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design guide 

from Tarmac Topblock

Design Contents 

Introduction 3 

Physical properties 4 

Structural design 6 

Thermal insulation 13 

Acoustic insulation 31 

Durability 42 

Movement control 45 

Safe handling 52 

Other information 

The information within this guide is designed to 

supplement the data given in the Tarmac Topblock 

product brochures: 

• Durox and Toplite – aircrete blocks 

• Hemelite and Topcrete – lightweight and dense 

aggregate blocks. 

In addition to the above, supplementary guidance is 

given in the following brochures: 

• Sitework Guide 

• Durox System – thin joint blockwork 

• Product Health and Safety guide. 

All of our technical information is held on 

www.topblock.co.uk 

2 www.topblock.co.uk

Design Introduction 

The UK’s top 

block solution 

Tarmac Topblock is the UK’s leading 

manufacturer of concrete blocks 

with specifications to match the 

most demanding of building 

requirements. With a unique 

product range including aircrete, 

dense and lightweight aggregate 

blocks, Tarmac Topblock is able to 

offer a product for every 

application from an extensive 

network of production facilities. 

At Tarmac Topblock we are 

committed to meeting our 

customers’ requirements through: 

• A programme of continuous 

research and development, 

resulting in a product range that 

is constantly updated to reflect 

the changing demands of the 

building industry 

• Strategically located sales offices 

serving local, regional and 

national customers supported by 

an experienced field sales team 

• Dedicated technical services 

providing advice on applications 

and the suitability of Tarmac 

Topblock products to specifiers 

and housebuilders 

• Maintaining a high standard of 

environmental, quality and 

health and safety performance, 

through the adoption of 

management systems meeting 

recognised international 

standards 

• Continued investment in block 

manufacturing capability. 

Durox and Toplite 

The aircrete range comprises two 

well-known product brands, Durox 

and Toplite. Aircrete is a modern 

construction material, which is able 

to adapt in response to changing 

regulatory requirements. Whilst it 

is used extensively because of its 

exceptional thermal insulation and 

low unit weight, it is a versatile 

material which is able to provide 

solutions below ground in 

foundation walls, in suspended 

beam and block floors, and all 

types of internal and external 

walling. 

For many years, Durox and Toplite 

products have been used for the 

inner leaf of cavity walls in 

conjunction with various insulation 

materials, making a valuable 

contribution to the overall thermal 

performance of the building. 

More recently the introduction of 

thin joint blockwork has seen 

Durox System providing a fast build 

method by adapting techniques 

proven in Europe to suit UK 

construction methods. 

Hemelite 

and Topcrete 

Continuous product development 

has led to an extensive range of 

lightweight and dense aggregate 

blocks, supplied from a network of 

production units located 

throughout the country. 

Hemelite lightweight aggregate 

blocks are suitable for use in walls 

above and below ground, and in 

block and beam floors. They have a 

proven high level of technical 

performance and provide a strong 

background to receive fixings 

and finishes. 

Topcrete dense aggregate blocks 

are extremely durable and have 

excellent loadbearing and sound 

insulation properties. Recent 

developments have seen the 

introduction of Multicore and RPW 

blocks, both of which have been 

designed to make them convenient 

to handle on site, whilst retaining 

good technical performance. The 

benefits of ease of handling will 

assist contractors and specifiers in 

meeting the obligations of the 

Construction (Design and 

Management) Regulations. 

Both Hemelite and Topcrete are 

produced in solid, hollow or 

cellular units and are available in 

Standard texture and closetextured 

Paint Quality grades. 

3 National Sales Helpline: 0845 606 2468

Design Physical properties 

Table 1: Durox aircrete blocks 

Supabloc Supabloc Supabloc Foundation System Floor Coursing 

4 7* 500/600/700 bricks 

Compressive strength to BS EN 771-4 (N/mm 2 ) 

3.6 4.2 7.3 3.6 & 7.3 3.6, 4.2 & 7.3 3.6 3.6 & 7.3 

Material dry density (kg/m 3 ) 

460 630 680 460 & 630 460, 630 & 680 460 460 & 680 

Thermal conductivity (W/mK) @ 3% moisture content 

0.11 0.16 0.19 0.11 & 0.19 0.11, 0.16 & 0.19 0.11 0.11 & 0.19 

Moisture movement (mm/m) (shrinkage) 

< 0.70 for all products 

Typical airtightness (m 3 (h.m 2 ) @ 50 Pa) 

100mm blocks - no finish 0.12 for all products 

Note*Supabloc 10 is available to special order, see the Durox product brochure for further details. 

Table 2: Toplite aircrete blocks 

GTI Standard ‘7’ Foundation Floor Coursing bricks 


2.9 3.6 7.3 3.6 & 7.3 3.6 2.9, 3.6 & 7.3 


460 630 730 630 & 730 630 460, 630 & 730 


0.11 0.15 0.19 0.15 & 0.19 0.15 0.11, 0.16 & 0.19 

Moisture movement (mm/m) (shrinkage) 

< 0.70 for all products 

Typical airtightness (m 3 (h.m 2 ) @ 50 Pa) 

100mm blocks - no finish 0.12 for all products 

4 

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Design Physical properties 

Table 3: Hemelite aggregate blocks 

Standard 

Paint Quality 


Solid blocks 3.6, 7.3 & 10.4* 3.6, 7.3 & 10.4* 

Cellular and hollow blocks 3.6 3.6 & 7.3* 


Solid, cellular or hollow 3.6 N/mm 2 1360 1400 

Solid 7.3 N/mm 2 1450 1400 

Solid 10.4 N/mm 2 1520 1500 

Solid Ultra - 1050 


Solid, cellular or hollow 3.6 N/mm 2 0.45 0.46 

Solid 7.3 N/mm 2 0.47 0.46 

Solid 10.4 N/mm 2 0.49 0.48 

Solid Ultra 3.6 N/mm 2 and 7.4 N/mm 2 - 0.38 

Moisture movement (mm/m) (shrinkage and expansion) 

Design Structural design 

Design principles 

Building Regulation A1 1 requires 

buildings to be constructed so 

the combined dead, imposed 

and wind loads are sustained 

and transmitted safely, without 

causing deflection or 

deformation in any part of the 

building. 

Many masonry structures can be 

designed to meet those 

requirements by using 

prescriptive rules in Building 

Regulations and British 

Standards, without the need for 

detailed structural calculations. 

Those rules apply to: 

• Houses and other small 

buildings up to three storeys in 

height; see Approved 

Document A 2 (2004 edition) 

and BS 8103-2: Part 2: 

‘Structural design of low-rise 

buildings’ 

• Non-loadbearing partitions: 

determination of thickness 

according to panel length, 

height and degree of fixity is 

contained in BS 5628-3. For 

structures outside the scope of 

those rules, design methods 

are contained in BS 5628: 

‘Code of practice for use of 

masonry’ which consists of the 

following parts: 

i) BS 5628-1 Structural use of 

unreinforced masonry 

ii) BS 5628-2 Structural use of 

reinforced and prestressed 

masonry 

iii)BS 5628-3 Materials and 

components, design and 

workmanship 

1 For Scotland refer to Section 1 

of The Building (Scotland) 

Regulations 

2 For Scotland refer to the Small 

Buildings Guide. 

Blockwork 

construction options 

To avoid designing with heavy 

masonry units, a number of 

construction and product options 

are available for constructing 

190-215mm width solid walls. 

These solutions are summarised 

below. In addition to good 

loadbearing potential, these 

constructions can also provide 

very good levels of fire resistance 

and sound insulation 

• Lay 440 x 100 x 215mm 

Topcrete Standard blocks flat 

(aspect ratio 0.46) to construct 

215mm wide walls 

• Use 290 x 190 x 140mm 

Topcrete RPW blocks (aspect 

ratio 0.74) to construct 

190mm wide walls 

• Lay 290 x 140 x 215mm 

Topcrete Midi blocks (aspect 

ratio 1.54) to construct 140mm 

walls. This block may also be 

laid flat to give a wall 215mm 

thick (aspect ratio 0.65). 

The use of heavy units can also 

be avoided by using a doubleleaf 

collar jointed wall. This is 

particularly suited to 

constructing 190mm or 215mm 

wide walls with both faces built 

fair. 

These walls can be designed as a 

cavity or single leaf wall. 

Characteristic compressive 

strengths for both of these 

conditions can be obtained from 

BS 5628-1. When designing as a 

single leaf wall, the leaves may 

be tied together using suitable 

metal ties or bed joint 

reinforcement. For blockwork, 

bed joint reinforcement can also 

be used to enhance its lateral 

load resistance, as well as 

increasing the spacing of 

movement joints. 

It is not practical to fully fill the 

collar joint with mortar and 

BS 5628-1 does not stipulate this 

as a requirement as it once did. 

Fig 1. Double-leaf 

collar jointed wall 

Reinforcement 

Collar joint 

Fig 2. Wide wall from 

blocks laid flat 

6 

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Blockwork 

construction 

options (continued) 

For other situations the use of 

heavy units e.g. those exceeding 

20kg, can be avoided as follows: 

• Change the block specification. 

• Select an alternative face size 

solid unit such as Topcrete 

Midi or RPW, or 

• Select a Hemelite or Topcrete 

cellular or hollow unit instead 

of a solid block, without 

compromising essential 

requirements. 

Characteristic 

compressive 

strength of 

blockwork 

For the convenience of designers, 

the characteristic compressive 

strength of blockwork (fk) can be 

used in conjunction with Tarmac 

Topblock products are shown in 

the following tables. It includes 

fk values for walls incorporating 

solid and voided units, as well as 

for walls to be built using blocks 

laid flat or laid back to back. 

Solid blocks 

The aspect of ratio of a block – 

the ratio of height to thickness – 

affects the characteristic 

compressive strength of the 

blockwork masonry, termed f k . 

The values for f k given in Table 5 

apply to Tarmac Topblock 

products laid in normal aspect. 

215mm 

Where 100mm solid blocks are 

laid flat (aspect ratio 0.46) the f k 

values in Table 8 should be used. 

Cellular or hollow 

blocks 

The compressive strength of 

cellular or hollow blocks is based 

on their gross area; no allowance 

need be made for the voids. 

Where the voids will be 

completely filled with concrete 

in-situ, the compressive strength 

should be calculated on the net 

area of the block, provided the 

28 day cube strength of the 

infilling concrete is not less than 

the net strength of the block. 

Characteristic compressive values 

can be obtained from Table 6. 

Width 

Notes 

Double-leaf collar 

jointed walls 

For double-leaf collar jointed 

walls designed as a single leaf 

wall, the f k values in Table 7 

should be used. These are 

applicable to walls in a thickness 

range of 190-215mm. 

Blocks laid flat / 

alternative unit 

aspect ratios. 

When designing walls using 

blocks laid flat, the f k values in 

Table 8 should be used. 

For walls constructed of 140mm 

height units, such as Hemelite 

Foundation blocks and Topcrete 

RPW blocks, the f k values in 

Table 8a should be used. 

Table 5: Characteristic compressive strength of 

blockwork, f k , in N/mm 2 using solid blocks 

(Group 1 units) 

Compressive strength 2.9 3.6 4.2 7.3 8.7 10.4 17.5 22.5 

of units (N/mm 2 ) 

Block width: 

characteristic compressive strength, f k (N/mm 2 ) 

75mm - 3.5 - 6.4 - - - - 

90mm - 3.5 - 6.4 - 8.2 10.1 12.0 

100mm 2.8 3.5 4.1 6.4 6.9 8.2 10.1 12.0 

115mm 2.7 3.3 3.9 6.1 - - - - 

125mm 2.5 3.1 3.6 5.8 - - - - 

130mm 2.4 3.0 - 5.6 - - - - 

140mm 2.3 2.9 - 5.3 5.8 6.8 8.4 10.0 

150mm 2.2 2.8 - 5.1 - 6.5 8.1 9.6 

190mm 1.9 2.4 - 4.4 - 5.7 7.0 8.3 

200mm 1.9 2.3 - 4.3 - 5.5 6.8 8.0 

215mm 1.8 2.2 2.6 4.1 - 5.3 6.5 7.7 

260mm 1.6 2.0 - 3.7 - - - - 

275mm 1.6 1.9 - 3.6 - - - - 

280mm 1.6 1.9 - 3.6 - - - - 

300mm 1.5 1.8 - 3.5 - - - - 

1. Blocks have a height of 215mm and are laid in normal aspect 

2. This Table is applicable to aircrete and aggregate blocks from the Tarmac 

Topblock range 

3. All values shown are for blockwork built with designation (iii) mortar. Values 

for blockwork built with mortar of other designations may be determined 

from BS 5628-1 

4. Check the individual product brochures for availability of sizes and strengths 

7 Technical Services: 0870 242 1489


Width 

215mm 

Table 6: Characteristic compressive strength of blockwork, f k , in N/mm 2 , using 

cellular or hollow blocks (Group 2 units) 

Compressive strength of unit (N/mm 2 ) 3.6 7.3 10.4 

Block width: 

100mm 3.5 6.1 7.1 

140mm 2.9 5.1 5.9 

190mm 2.4 4.2 4.9 

215mm 2.2 3.9 4.6 

215mm 

Notes 

Width 

1. This Table is applicable to units in the Hemelite and Topcrete ranges 


3. All values shown are for blockwork built with designation (iii) mortar. Values for blockwork built with mortar of other 

designations may be determined from BS 5628-1 

4. Check the individual product brochures for availability of sizes and strengths 

Table 7: Characteristic compressive strength, f k , in N/mm 2 , of collar jointed 

walls built with aggregate blocks having a block height/wall thickness ratio 

of between 1.0 and 1.2 

Compressive strength of unit (N/mm 2 ) 3.6 7.3 10.4 17.5 22.5 

Mortar group (iii) 2.4 4.0 5.1 7.0 8.3 

Mortar group (ii) 2.8 4.5 5.7 7.9 9.4 

Mortar group (i) 3.4 5.5 7.0 9.7 11.6 

100mm 

Notes 

215mm 



3. Suitable ties or bed joint reinforcement should be used to connect the leaves together 

Table 8: Characteristic compressive strength, f k , in N/mm 2 , of walls built with 

aggregate blocks laid flat having an as laid height / wall thickness ratio of 

between 0.4 and less than 0.6 

Compressive strength of unit (N/mm 2 ) 3.6 7.3 10.4 17.5 22.5 

Mortar group (iii) 2.5 4.1 5.2 7.0 8.1 

Mortar group (ii) 2.9 4.6 5.9 7.9 9.1 

Mortar group (i) 3.5 5.6 7.2 9.7 11.3 

140mm 

Notes 

Width 


2. The values shown would normally be applicable to 100mm thickness blocks laid flat used to construct a 

215mm width wall 

3. Unit strengths are those for units tested in the normal aspect 

Table 8a: Characteristic compressive strength, f k , in N/mm 2 of walls built with 

140mm high blocks 

Compressive strength of unit (N/mm 2 ) 2.9 3.6 4.2 7.3 8.7 10.4 17.5 22.5 

Block width: 

190mm (RPW) - - - 3.5 - - - - 

215mm (Any 140mm block laid flat) 1.5 1.8 2.1 3.3 3.6 4.2 5.3 6.2 

255mm (Hemelite Foundation) - - - 4.1 - - - - 

275mm (Topcrete Foundation) - - - 4.1 - - - - 

Note 

All values shown are for blockwork built with designation (iii) mortar. Values for blockwork built with mortar of other 

designations may be determined from BS 5628-1 


Design Unreinforced walls 

Partial safety factors 

Tarmac Topblock products are 

manufactured under an ISO 9001: 

2000 quality assurance system. 

All units conform to Category 1 

manufacturing control allowing 

enhanced safety factors to be 

adopted in the design of 

masonry walls. Consequently, the 

partial safety factors for material 

strength given in Table 9 may be 

employed. 

Laterally loaded 

walls 

Recommendations for walls 

subject to lateral loading are 

given in BS 5628-1. Such loading 

must be taken into account when 

the lateral load is predominant 

and when the wall must be 

designed to resist accidental 

damage. 

Table 10: Section properties 

of blockwork 

Block 

width 

(mm) 

Section modulus 

(Z), per metre 

length (cm 3 /m) 

90 1350 

100 1667 

125 2604 

140 3267 

150 3750 

190 6017 

200 6667 

215 7704 

Table 9: Partial safety factors for material strength using 

Tarmac Topblock products 

Category of 

Category of 

Masonry Units construction control 

Special Normal 

Compression (ϒ m ) Category I 2.5 3.1 

Category II 2.8 3.5 

Flexure (ϒ m ) Category I and II 2.5 3.0 

The characteristic flexural 

strength of blockwork, f kx , is 

given in BS 5628-1: Table 3 and 

relates broadly to the 

compressive strength of the units 

(water absorption is not a 

relevant factor). The values apply 

to walls built with solid, cellular 

and hollow blocks. The section 

properties of blockwork are 

shown in Table 10. 

Non-loadbearing 

internal walls 

Unless internal walls or partitions 

are designed to be freestanding 

they should be laterally 

restrained. Horizontal or vertical 

supports may be either 

continuous or intermittent. 

The length and height of the 

wall in relation to its thickness 

should fall below the relevant 

line on the graphs on page 10. 

Where it is known that an 

internal wall is to be plastered, a 

maximum of 13mm of plaster to 

one or both sides may be 

included when determining the 

wall thickness, e.g. for 100mm 

width blockwork plastered both 

sides the overall wall thickness is 

126mm, therefore, it would be 

appropriate to use the 125mm 

line on the graph. In such cases, 

consideration should be given to 

the need for temporary support 

prior to plastering. 

Consideration should also be 

given to the following factors, 

which may affect the stability of 

the wall: 

a) accommodation of movement 

b) openings 

c) the likelihood of exceptional 

lateral loading owing to the 

nature of the building 

d) wind load (see BS 6399-2). 

In addition, increased thickness 

may be required to take account 

of other performance 

requirements such as sound 

insulation or fire resistance. 


Design Unreinforced walls 

Table 11: Wall restrained at top only 

9 

8 

Unrestrained height (m) 

7 

6 

5 

4 

3 

2 

1 

0 

2 3 4 5 6 7 8 9 10 11 12 

Unrestrained length (m) 

Wall thickness (mm) 

215 

190 

150 

140 

125 

115 

100 

90 

75 

Table 12: Wall restrained at both ends only 

9 

8 


7 

6 

5 

4 

3 

2 

1 

0 

2 3 4 5 6 7 8 9 10 11 12 



215 

190 

150 

140 

125 

115 

100 

90 

75 

Table 13: Wall restrained at both ends and top 

9 

8 


7 

6 

5 

4 

3 

2 

1 

0 

2 3 4 5 6 7 8 9 10 11 12 



190 

150 

140 

125 

115 

100 

90 

75 

10 


Design Reinforced walls 

Reinforced walls 

Adding reinforcement to 

blockwork improves both the 

vertical loadbearing capacity and 

the bending resistance of the 

masonry. 

Reinforced blockwork should be 

constructed in accordance with 

the recommendations of BS 

5628-2. Further guidance for 

reinforced freestanding walls is 

given in BRE Good Building 

Guide (GBG) 19, and for 

reinforced retaining walls in 

GBG 27. 

Guidance on the design and 

construction of masonry 

retaining walls suitable for 

basements is given in the 

Approved Document ‘Basements 

for Dwellings’. 

There are two common methods 

of forming reinforced 

blockwork: 

• placing reinforcement and 

concrete in the cores of 

hollow blocks. Typically 

215mm Topcrete hollow 

blocks can be considered for 

this application 

Fig 3. Reinforcement: using 

Topcrete hollow blockwork 

• placing reinforcement and 

concrete in the cavity 

between two leaves of 

blockwork; this construction 

is known as grouted-cavity 

masonry. 

450mm 

Fig 4. Reinforcement: 

grouted-cavity masonry 

Mortar mixes for reinforced 

blockwork should be designation 

(i) or (ii) according to BS 5628-2. 

However, designation (iii) mixes 

may be used if the lateral load 

resistance is enhanced by bed 

joint reinforcement. 

Concrete infill should be a 

minimum of grade 25 as 

described in BS 5328; 

alternatively the following 

volume proportions may be 

used: 1:1/4:3:2 cement: lime: 

sand: aggregate, using 

aggregate not greater than 

10mm. 

Cover to 

reinforcement 

Grouted cavity at 

least 100mm wide 

When determining fire resistance 

the block may be considered as 

forming part of the cover to the 

reinforcement, in accordance 

with BS 8110-2. However, when 

the durability of the 

reinforcement is being assessed, 

only the thickness of the 

concrete infill can be considered 

as forming the cover to the 

reinforcement (see Fig. 5). The 

minimum concrete cover 

required for durability under a 

range of exposure conditions is 

given in BS 5628-2 Table 12. 

Fig 5. Determination of cover for 

fire resistance and durability 

(1) 

Notes 

Concrete infill 

Design of walls with 

Durox System 

Durox System is thin jointed 

blockwork using 2-3mm mortar 

joints. Characteristic compressive 

strength values are given in 

BS 5628-1, and may be taken as 

the values given for mortar 

strength class M12 (mortar 

designation (i) in Table 2 of this 

Standard. Similarly the 

characteristic flexural strength 

may be taken as the values given 

for mortar strength class M12 

(mortar designation (i) in Table 3 

of this Standard. 

For further advice refer to the 

Durox System brochure. 

(2) 

(1) Thickness of cover for 

determination of fire resistance 

(2) Thickness of cover for 

determination of durability 

11 

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Design Reinforced walls 

Eurocode 6 Design 

of Masonry 

Structures 

(BS EN 1996) 

Eurocode 6 will eventually 

replace BS 5628: Parts 1, 2, & 3. 

However, until the Draft National 

Annexes and a complementary 

British Standard covering aspects 

of BS 5628 not addressed by 

Eurocode 6 have been published, 

it is unlikely that designing 

masonry structures to the 

Eurocode 6 will prove attractive 

to designers. 

BS 5628: 1, 2, & 3 are proposed 

to be withdrawn in 2011. 

The relevant parts of Eurocode 6 

are shown in Table 14 below: 

Table 14 

Eurocode Part Full title Publication date Supercession details 

BS EN 1996-1-1 Eurocode 6 30/12/2005 BS 5628-1: 

Design of masonry BS 5628-2 

structures 

Common rules for 

reinforced and 

unreinforced 

masonry structures 

BS EN 1996-1-2 Eurocode 6 30/06/2005 Parts of BS 5628-3 

Design of masonry 

structures 

Structural fire design 

BS EN 1996-2 Eurocode 6 15/02/2006 BS 5628-3 


structures 

Design considerations, 

selection of materials 

and execution of 

masonry 

BS EN 1996-3 Eurocode 6 15/03/2006 - 


structures 

Simplified calculation 

methods for 

unreinforced 

masonry structures 

12 


Design Thermal insulation 

This section has been prepared 

to give designers and users a 

concise overview of the new 

Part L standards for the 

conservation of fuel and power 

in buildings. 

Its main purpose is to highlight 

the major changes embodied in 

Approved Document L (2006 

edition) and give guidance on 

the revised methods of 

compliance and the design tools 

required to calculate the overall 

energy efficiency of buildings. 

For any building the cost 

effective design of walls and 

floors is paramount, and usually 

one of the first areas sought to 

establish compliance. A number 

of wall and floor construction 

solutions are presented using 

Tarmac Topblock products. Such 

constructions are practical to 

build and based on concepts that 

are tried and trusted and offer 

little or no risk to specifiers and 

end users. 

can only be practically achieved 

by the use of approved software. 

In the case of dwellings Tarmac 

Topblock is able to offer its 

specifiers and end users design 

solutions based on the latest BRE 

approved SAP 2005 software. 

A charge will be made to cover 

administration costs, but overall 

this offers great value to users of 

our Tarmac Topblock products. 

This section also includes case 

studies for new build dwellings. 

These are intended to illustrate 

the sort of measures that will be 

required to satisfy Part L 

together with the associated 

floor, wall and roof U-values. 

Although construction 

techniques will not alter 

significantly in meeting the new 

Part L standards there is a new 

approach to the calculation of 

energy, to the extent that this 

13 



Background to the 

new Part L 

Part L objectives 

The new standards in thermal 

efficiency are intended to 

support the Government’s 

commitment to reduce CO2 

emissions, saving an estimated 

one million tonnes of carbon 

every year. 

To satisfy the requirements of 

the Energy Performance Building 

Directive, improved energy 

performance standards of 

20%-27% have been set for all 

new buildings. This is based on a 

‘whole building’ CO2 Target 

approach - see Table 15. 

Table 15 - Part L Summary Chart 

New Build 

Refurbishment 

(inc. extensions, 

alterations and 

change of use) 

Dwellings 

• 20% better than 2002 standards based 

on notional building (Elemental U-values) 

• Whole building CO2 target determined 

using SAP 2005 

• Minimum permitted fabric standards. 

(Limiting U-values set for walls, floors, 

roofs, windows and doors) 

• Air pressure testing on a sample basis 

• For renovations, extensions, changes of 

use, etc. Elemental U-values used to 

show compliance 

• SAP/Reduced SAP may be used as an 

alternative method of demonstrating 

compliance 

Buildings other than Dwellings 

• 27% better than 2002 standards based 

on notional building (Elemental U-values) 

• Whole building CO2 target determined 

using new methodology (Simplified 

Building Energy Model) 

• Minimum permitted fabric standards 

(Limiting U-values set for walls, floors, 

roofs, windows and doors) 

• Air pressure testing 

• For renovations, extension 1000m 2 to be upgraded when 

extended and when services are first 

installed or enlarged (cost limited to 

10% of principal works) 



New Part L Approved 

Documents 

To support the improved 

standards required in energy 

efficiency, together with the 

implementation of the European 

Union’s Energy Performance of 

Building Directive (EPBD), a new 

set of Approved Documents has 

been published in relation to the 

following building types: 

• Approved Document L1A : New 

dwellings 

• Approved Document L1B : 

Work on existing dwelling 

• Approved Document L2A : New 

buildings – other than 

dwellings 

• Approved Document L2B : 

Existing buildings – other than 

dwellings. 

The new requirements took 

effect on the 6th April 2006. 

Second Tier reference 

documents 

The Approved Documents refer 

to a number of second tier 

reference documents which 

designers will need to familiarise 

themselves with. Some of these 

are listed below: 

• The Governments Standard 

Assessment Procedure for 

Energy Rating of Dwellings 

(2005 Edition) 

• Limiting thermal bridging and 

air leakage: Robust 

construction details for 

dwellings and similar buildings 

• Low or Zero Carbon Energy 

Sources: Strategic Guide 

(2006 Edition, 

ISBN 1-85946-224-3) 

• Domestic Heating Compliance 

Guide (2006 Edition, 

ISBN 1-85946-225-6) 

• Non Domestic Heating, 

Cooling and Ventilation 

Compliance Guide 


ISBN 1-85946-226-X). 

• The National Calculation 

Methodology for determining 

the energy performance of 

buildings Part 1: A guide to the 

application of the SBEM and 

other approved calculation 

tools for building regulation 

purposes in the UK 


ISBN 1-85946-227-8). 

• Accredited details 

Accredited Construction Details 

have (ACDs) have been 

developed to minimise cold 

bridging and improve 

airtightness. A full range of 

details for masonry construction 

are available on the following 

website: 

www.planningportal.gov.uk. 

15 



Complying with the 

new standards 

Methods of Compliance 

This is straightforward in that all 

new buildings must meet a set 

carbon dioxide emissions 

target based on a whole 

building energy performance 

approach. This replaced the 

‘elemental’ and ‘alternative’ 

methods of compliance allowed 

in the 2002 standards. 

The target CO2 emission rate 

(TER) is calculated using the 

following methodologies. 

L1A New Dwellings 

Using the Government’s 

Standard Assessment procedure 

(SAP) for Energy Rating or 

Dwellings, SAP 2005 edition. 

L2A New Buildings – other than 

Dwellings 

Using the Simplified Building 

Energy Model (SBEM), or other 

approved software tools that are 

approved as set out in Annex 1 

of ODPM Circular 04/2006. 

Key design factors 

In order to demonstrate 

compliance, the following 

factors will need to be addressed 

during the design of buildings. 

• Building type and 

configuration 

• Building fabric U-values 

• Glazed areas and orientation 

(solar gain) 

• Thermal bridging details 

(Accredited Construction Details) 

• Space heating and hot water 

• Ventilation (natural or 

mechanical) 

• Fixed lighting internal and 

external 

• Airtightness of the building 

fabric. 

Reasonable limit for design air 

permeability is 

10m 3 /(h.m 2 ) @ 50 Pa: 

Sample testing of new dwellings 

required. 

Elemental U-values 

For new buildings (L1A and L2A) 

meeting maximum Elemental 

U-values will no longer be valid 

as the sole means of 

demonstrating compliance. 

Whilst minimum acceptable 

performance standards for the 

building envelope are given 

compliance is achieved by 

calculating CO2 targets. 

However, the Elemental U-value 

route may be used to show 

compliance for extensions and 

refurbishment work to existing 

buildings. 

Wall solutions 

The Tarmac Topblock product 

range, Durox, Toplite, Hemelite, 

and Topcrete, provide extensive 

options for established, cost 

effective, solutions in all types of 

walling situations. 

In addition to the requirements 

for improved thermal insulation 

the Tarmac Topblock range of 

products provide the following 

benefits: 

• Structural strength 

• Fire resistance 

• Durability 

• Sound insulation 

• Resistance to moisture 

penetration 

• Frost resistance. 

Subject to energy calculations, 

for most applications external 

walls constructed in the range 

0.27-0.30W/m 2 K are likely to be 

found to provide acceptable 

performance levels. For 

constructions not featured 

contact the Technical Helpline on 

0870 242 1489. 

16 



Table 16 - Thermal properties 

Topblock Product Thermal Conductivity Compressive Strength* 

(W/mK) (N/mm 2 ) 

Durox Supabloc 0.11 3.6 

Durox Supabloc 4 0.16 4.2 

Durox Supabloc 7 0.19 7.3 

Toplite GTI 0.11 2.9 

Toplite Standard 0.15 3.6 

Toplite 7 0.19 7.3 

Hemelite 0.45, 0.47, 0.49 3.6, 7.3, 10.4 

Topcrete 1.28 3.6 – 22.5 

Note *Compressive strength to BS EN 771-3 & 4 

Table 17 - U-values using full fill cavity insulation (W/m 2 K) 

facing brick outer leaf • insulation • block • surface finish 

Dritherm insulation with Durox and Toplite aircrete blocks 

100mm Inner leaf 

Insulation 

Internal Finish 

Durox 

Supabloc 

Durox 

Supabloc 4 

Durox 

Supabloc 7 

75mm Dritherm 32 






13mm dense plaster 

13mm lightweight plaster 

12.5mm plasterboard 

Toplite GTI 

Toplite 

Standard 

Toplite 7 

0.29 0.31 0.32 

0.28 0.29 0.30 

0.29 0.30 0.31 

0.27 0.29 0.30 

0.28 0.30 0.30 

0.27 0.28 0.29 

Table 18 - U-values using full fill cavity insulation (W/m 2 K) 

facing brick outer leaf • insulation • block • surface finish 

Dritherm insulation with Hemelite lightweight and Topcrete dense aggregate 

Insulation 











Note *The thermal conductivity of Dritherm is 0.032 W/mK. 


Hemelite Standard Topcrete Standard 

0.32 0.34 

0.28 0.30 

0.32 0.34 

0.28 0.29 

0.31 0.33 

0.27 0.29 

17 

www.topblock.co.uk


Table 19 - U-values using partial fill cavity insulation (W/m 2 K) 

facing brick outer leaf • 50mm cavity • insulation • block • surface finish 

Kingspan insulation with Durox and Toplite aircrete blocks 


Insulation 


Durox 

Supabloc 

Durox 

Supabloc 4 

Durox 

Supabloc 7 

40mm Kingspan TW50 









Toplite GTI 

Toplite 

Standard 

Toplite 7 

0.29 0.31 0.32 

0.26 0.27 0.28 

0.29 0.30 0.31 

0.25 0.27 0.27 

0.28 0.29 0.30 

0.25 0.26 0.27 

Table 20 - U-values using partial fill cavity insulation (W/m 2 K) 

facing brick outer leaf • 50mm cavity • insulation • block • surface finish 

Kingspan insulation with Hemelite lightweight and Topcrete dense aggregate blocks 

Insulation 









Hemelite Standard Topcrete Standard 

0.30 0.31* 

0.29 0.31* 

0.28 0.30 

Note 

*These constructions can achieve a U-value of 0.30 W/m 2 K using 50mm Kingspan Kooltherm K8 in lieu of Kingspan TW50. 

The thermal conductivity of Kingspan TW50 is 0.023 W/mK and Kingspan K8 is 0.021 W/mK. The Kingspan low-e cavity has 

a thermal resistance of 0.64 m 2 K/W 

Table 21 - U-values using clear cavity with thermal laminate (W/m 2 K) 

facing brick outer leaf • 50mm cavity • block 

British Gypsum’s thermal laminate with Durox and Toplite aircrete blocks 

Insulation 


Durox Supabloc Durox Supabloc 4 Durox Supabloc 7 

Toplite GTI Toplite Standard Toplite 7 

60mm Thermaline Super 

0.27 0.29 0.30 


0.26 0.27 0.28 

Note Other thermal laminates of equivalent thermal resistance may be used 

Table 22 - U-values using clear cavity with thermal laminate (W/m 2 K) 

facing brick outer leaf • 50mm cavity • block 

British Gypsum’s thermal laminate with Hemelite lightweight and Topcrete dense aggregate blocks 

Insulation 


Hemelite Standard 

Topcrete Standard 


0.32 0.33 


0.30 0.31 

Note Other thermal laminates of equivalent thermal resistance may be used 

18 



Ground Floors 

Subject to energy calculation, for 

most applications ground floors 

will need to be constructed to 

meet a U-value of around 

0.20W/m 2 K. 

The U-value of a ground floor is 

dependent on the ratio of its 

perimeter and area (P/A). Table 

23 shown below indicates the 

thickness of insulation required 

for beam and block ground 

floors that are designed to meet 

a U-value of 0.20W/m 2 K. The use 

of Durox or Toplite Foundation 

blocks below ground will further 

improve the U-value of the 

floor, optimising the thickness 

of insulation that is required 

as shown. 

U-value example 

Determine the required 

insulation thickness to achieve a 

U-value of 0.20W/m 2 K for a 

beam and block floor comprising 

Hemelite infill blocks. 

6m 3m 

5m 

15m 

10m 

9m 

Solutions 

(i) Calculate the floor perimeter, P: 

P = 10 + 9 + 15 + 6 + 3 + 5 = 48m 

(ii) Calculate the floor area, A: 

A = (6 x 5) + (10 x 9) = 120m 2 

(iii) Ratio of P/A: 

P/A = 48/120 = 0.40 

(iv) From the following tables 

the thickness of added 

insulation can be found 

under the column heading 

P/A ratio = 0.4 

e.g. 120mm Jabfloor 70 

Table 23 - Beam & block ground floor to achieve U-value 0.20 (W/m 2 K) or better 

Floor Block Insulation type Insulation thickness 

P/A ratio 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 

Durox Jabfloor 70 20 75 95 105 110 115 120 120 125 125 

Durox Polyfoam 15 60 85 95 100 105 105 110 110 115 

Floorboard 220 

Durox Celotex 10 45 60 65 70 70 75 75 75 75 

Toplite Jabfloor 70 20 80 100 110 115 120 125 130 130 130 

Toplite Polyfoam 15 65 90 100 105 110 110 115 115 120 


Toplite Celotex 15 50 60 70 70 75 75 80 80 80 

Hemelite Jabfloor 70 30 90 110 120 125 130 135 135 140 140 

Hemelite Polyfoam 25 80 100 110 115 120 120 125 125 125 


Hemelite Celotex 20 55 65 75 80 80 85 85 85 85 

Topcrete Jabfloor 70 35 90 110 125 130 135 140 140 145 145 

Topcrete Polyfoam 25 80 100 110 115 120 125 125 130 130 


Topcrete Celotex 20 55 70 75 80 85 85 85 90 90 

Notes 

1. Floor beams are assumed at 515mm centres except Durox at 620mm centres. 

2. Some thicknesses of insulation are achieved by combining one or more layers to obtain the overall thickness. 

3. Floors finished with (minimum) 50mm screed or chipboard 

19 



Table 24 - Beam & block ground floor with Foundation blocks to achieve U-value 0.20 

(W/m 2 K) or better 

Floor Block Insulation type Insulation thickness 

P/A ratio 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 

Durox Jabfloor 70 - 60 85 95 105 110 110 115 120 120 

Durox Polyfoam - 45 70 85 95 95 100 105 105 110 


Durox Celotex - 35 50 60 65 65 70 70 70 75 

Toplite Jabfloor 70 - 65 90 100 110 115 120 120 125 125 

Toplite Polyfoam - 50 80 90 95 100 105 110 110 110 


Toplite Celotex - 40 55 60 65 70 70 75 75 75 

Hemelite Jabfloor 70 10 75 100 110 120 125 130 130 135 135 

Hemelite Polyfoam 10 60 90 100 105 110 115 115 120 120 


Hemelite Celotex 10 45 60 70 75 75 80 80 80 85 

Topcrete Jabfloor 70 20 80 100 115 120 125 130 135 135 140 

Topcrete Polyfoam 15 65 90 100 110 115 120 120 125 125 


Topcrete Celotex 10 50 65 70 75 80 80 80 85 85 

Notes 

1. Floor beams are assumed at 515mm centres except Durox at 620mm centres 

2. Durox or Toplite Foundation blocks, 3.6 N/mm 2 , are assumed 300mm thick, to a depth of 675mm below external ground level 

3. Some thicknesses of insulation are achieved by combining one or more layers to obtain the overall thickness 

4. Hyphen (-) denotes no insulation required over floor to achieve U-value 

5. Floors finished with (minimum) 50mm screed or chipboard 

New Dwellings (L1A) 

Demonstrating compliance 

Compliance is demonstrated by 

meeting the five criteria set out 

below: 

1. The Dwelling Emission Rate 

(DER) is not greater than the 

Target Emission Rate (TER) 

2. The performance of the 

building fabric and fixed 

building services are no worse 

than set design limits. 

3. The dwelling has appropriate 

passive control measures to 

limit the effect of solar gains 

on indoor temperatures in 

summer. 


“as built” dwelling is 

consistent with the DER. 

5. The necessary provisions for 

energy efficient operation of 

the dwelling are put in place. 

Methodology document – 

SAP 2005 

SAP worksheet and specification 

can be downloaded from 

www.bre.co.uk/sap2005 

1. Dwelling Emissions Rates. It is 

advisable to calculate the 

dwelling emissions rate at the 

design stage. A final “as built” 

calculation is required to 

reflect any changes that 

occurred during construction. 

How to comply 

Using SAP 2005, the CO2 

emission rate is calculated for a 

notional dwelling of the same 

size and shape as the proposed 

dwelling, using a fixed set of 

reference values for the fabric 

heat loss, building services and 

fuel type. The calculated CO2 

emission rate is equivalent to 

dwelling constructed to 2002 

thermal standards. 

Table 25 lists the reference 

U-values used to calculate the 

CO2 emission rate for the 

notional building. 

The TER is determined by 

reducing the notional buildings 

CO2 emission rate by 20%, and 

making an allowance for any 

change to the main heating fuel 

using the ‘fuel factor’ 

(see Table 26). 

The SAP calculation is repeated 

but this time inserting the 

proposed U-values, air 

permeability, building services, 

fuels and low or zero carbon 

energy sources for the proposed 

building. 

This results in the Dwelling 

Carbon Emission Rate (DER). If 

the DER of the proposed building 

is less than the TER the first 

criteria has been achieved. 



Table 25: Reference U-values used in the notional dwelling* 

Element 

U-value (W/m2K) 

Wall 0.35 

Floor 0.25 

Roof 0.16 

Windows and doors 2.00 

Note *A full set of reference values is given in Appendix R of SAP 2005 

Table 26: Fuel Factor 

Element 

Fuel Factor 

Mains gas 1.00 

LPG 1.10 

Oil 1.17 

Grid electricity 

(for direct acting storage and electric heating pumps) 1.47 

Solid mineral fuel 1.28 

Renewable energy, incl. bio-fuels such as wood pellets 1.00 

Solid multi-fuel 1.00 

2. Limits on design flexibility 

Show that the thermal 

performance of the building 

fabric and the heating, hot water 

and lighting systems are within 

the design limits. 


Design limits for envelope 

standards 

Limiting U-values for the 

building fabric are stipulated in 

Approved Document L1A and 

these are summarised in Table 27. 

The averaged weighted U-value 

for any of the elements listed in 

column (a) should not be 

exceeded. However, to achieve 

the TER the envelope standards 

for most of the elements will 

need to be significantly better 

than those shown. 

No individual area of an element 

should exceed the values shown 

in column (b) in order to 

minimise condensation risk e.g. 

recess for external meter box. 

The new ADL also sets out 

limiting criteria for: 

• Air permeability 

• Heating and hot water systems 

• Insulation of pipes ducts and 

heating vessels 

• Mechanical ventilation and 

cooling 

• Fixed lighting internal 

and external 

Table 27: Limiting U-values 

Element (a) Area-weighted average U-value (b) Limiting U-value 

(W/m 2 K) (W/m 2 K) 

Wall 0.35 0.70 

Floor 0.25 0.70 

Roof 0.25 0.35 

Windows and doors 2.20 3.30 

21 



New Dwellings (L1A) 

(continued) 

3. Limiting solar gains in summer 

Provision should be made to 

prevent high internal 

temperatures due to excessive 

solar gain. 


Designers can calculate if there is 

a high risk that solar gains will 

result in high internal 

temperatures in accordance with 

Appendix P of SAP 2005. The use 

of air conditioning in housing 

should be discouraged. 

Further guidance is given in 

‘CE 129 Reducing overheating, a 

designers guide’ which can be 

downloaded from The Energy 

Saving Trust website at 

www.est.org.uk. 

4. Quality of construction and 

commissioning 

Demonstrate that the 

performance of the dwelling as 

built is consistent with the DER. 

Demonstrate that the quality of 

construction has been achieved 

by adopting Accredited Details 

and undertaking an air pressure 

test to confirm the specified 

design air permeability has been 

achieved. 

permeability standards have 

been met. A reasonable limit for 

design air permeability would be 

10m 3 /(h.m 2 ) @ 50Pa. Suitable 

site inspection is required to 

confirm satisfactory installation 

of insulation to minimise thermal 

bridging. 

Commissioned heating and hot 

water systems to be signed off by 

a competent person. A final 

calculation of the DER should be 

based on the dwelling as 

constructed, including any 

changes made and the results of 

the air permeability test. 

5. Providing information 

Provide operating and 

maintenance instructions to 

enable the building and its 

services to be operated in an 

energy efficient manner. 


The owner of the building should 

be provided with a set of 

operating and maintenance 

instructions to optimise the 

efficiency of the dwelling in use. 

Provide notice that the building 

services are in accordance with 

the proposed building design 

and have been inspected, tested 

and commissioned. 


An air pressure test, by an 

accredited tester, must be carried 

out to show that minimum air 

Air pressure testing 

24 22 



Case studies 

Assuming 2002 levels of heating 

controls and air permeability, 

case study 1 shows the fabric 

U-values required to give a PASS 

under the new regulations when 

applied to a standard 3 bed 

semi-detached or end 

terraced property. 

Case Study 1: 3 bed semi or end terrace (73.6m2 floor area) 

Building Fabric Insulation 

Element U-value (W/m 2 K) Area (m 2 ) Heat loss (W/K) 

Ground floor 0.18 37.74 6.89 

Walls 0.26 72.64 18.89 

Roof 0.14 37.74 5.28 

Windows/doors 1.80 15.00 27.00 

Space/Water Heating 

Boiler 

90.3% SEDBUK, gas fired 

Controls 

Programmer, roomstat + TRVs 

Secondary heating None 

Air Permeability 

Design value of 10m3/(h.m2) @ 50Pa 

TER 

DER 

23.69 23.58 

PASS 

Improving the air tightness of 

the dwelling will have a 

significant effect on the overall 

performance of the dwelling. 

Case study 1a below, shows how 

an improved air permeability 

rate together with improved 

space heating controls can allow 

the wall U-value to be increased 

from 0.26 to 0.30W/m 2 K. 

Case Study 1a: 3 bed semi or end terrace (73.6m2 floor area) 



Ground floor 0.18 37.74 6.89 

Walls 0.30 72.64 21.76 

Roof 0.14 37.74 5.28 

Windows/doors 1.80 15.00 27.00 


Boiler 


Controls 

Time and temperature zone control 




TER 

DER 

23.69 23.64 

PASS 



Case Study 2: 3 bed mid terrace (73.6m2 floor area) 



Ground floor 0.18 37.74 6.89 

Walls 0.30 55.44 16.63 

Roof 0.14 37.74 5.28 

Windows/doors 1.80 15.00 27.00 


Boiler 


Controls 





TER 

DER 

22.55 22.61 

FAIL 

It should be noted that what may 

appear to be a worse case 

situation is not always the case. 

For example, the semi detached 

dwelling shown in case study 1a 

above passes with the 

specification given. However, 

when the same dwelling using the 

same specification is plotted as 

mid terrace it fails, case study 2. 

Such cases will require a slight 

Case Study 2a: 3 bed mid terrace (73.6m2 floor area) 



Ground floor 0.18 37.74 6.89 

Walls 0.29 55.44 16.08 

Roof 0.14 37.74 5.28 

Windows/doors 1.80 15.00 27.00 


Boiler 


Controls 





TER 

DER 

22.55 22.53 

PASS 

modification such as improving 

the wall U-value as shown in 

case study 2a. 

In practice it is likely that the 

higher specification required for 

the worst case will be adopted. 

However, for buildings 

containing multiple dwellings 

(such as a terrace of houses or 

flats), AD L1A permits an average 

TER and DER for the building to 

be calculated to show 

compliance, see case study 3. 

24 



Case Study 3: Terrace of 3 houses (73.6m2 floor area each unit) 

Unit 

TER DER Floor Area (A) (m 2 ) TER x A DER x A 

End terrace unit 

(from Case study 1a) 

23.69 23.64 73.6 1743.58 1739.90 

Mid terrace unit 

(from Case study 2) 

22.55 22.61 73.6 1659.68 1664.09 

End terrace unit 

(from Case study 1a) 

23.69 23.64 73.6 1743.58 1739.90 

Totals 

220.8 5146.84 5143.89 

Average TER for building = 5146.84/220.8 = 23.31 

Average DER for building = 5143.89/220.8 = 23.30 

PASS 

Note 

The individual TER & DER for each dwelling are still required 

Effect of secondary 

heating 

SAP 2005 assumes that 10% of 

the heating demand will be met 

by a secondary heating system. 

Where no secondary heating is 

specified, electric room heaters 

must be assumed unless a 

chimney or flue is provided – 

in which case an open solid fuel 

fire (37% efficiency) or 

decorative fuel effect gas fire 

open to chimney (20% efficiency 

must be assumed depending on 

whether a gas point is provided 

or not. 

Case study 4 shows a 

specification, which works, for a 

typical 3 bedroom detached 

house. As no secondary heating 

has been specified, and no flues 

or chimneys will be provided, 

electric room heaters are 

assumed to provide secondary 

heating. 

Case Study 4: 3 bed detached (119.3m2 floor area) 



Ground floor 0.18 60.67 11.15 

Walls 0.30 126.50 37.95 

Roof 0.14 60.67 8.49 

Windows/doors 1.80 25.40 45.73 


Boiler 


Controls 

Timer and temperature zone control 

Secondary heating Not specified – Electric room 

heaters assumed 



TER 

DER 

21.92 21.80 

PASS 

If a chimney or flue is to be 

provided, the carbon emission 

calculations for the dwelling 

given in case study 4 will be 

affected as shown in case study 

4a. This highlights the need to 

specify the secondary heating at 

an early stage as the assumptions, 

which would otherwise be 

required to be made, could lead 

to an un-economic and over 

specified design. 

25 



Case Study 4a: 3 bed detached (119.3m2 floor area) 

Secondary Heating 

Assumed as: 

• Not specified 

Solid fuel burning open fire in grate 

• Chimney or flue provided 

(37% efficiency) 

• No gas point 

TER 

DER 

21.92 25.70 

FAIL 


Assumed as: 

• Not specified 

Solid fuel burning open fire in grate 

• Chimney or flue provided 

(37% efficiency) 

• Adjacent g.as point 

TER 

DER 

21.92 24.46 

FAIL 


Assumed as: Specified appliance 

• Specified as: Flush fitting live effect gas 

fire, sealed to chimney (50% efficiency) 

TER 

DER 

21.92 21.63 

PASS 

Conclusion 

No one measure can achieve the 

overall 20% CO2 emissions 

savings; this is a significant step 

change that will require changes 

to the complete specification. 

Specifiers and end users must 

decide on the most appropriate 

package of measures for the 

fabric insulation, air permeability 

and fixed services to meet the CO2 

targets in a cost effective way. 

26 

www.topblock.co.uk


New Buildings – 

Other than 

Dwellings (L2A) 

Demonstrating compliance 

Compliance with AD L2A is 

similar to the principles set out 

for AD L1A but using SBEM 

methodology rather than 

SAP 2005. 

Compliance is demonstrated 

by meeting the following 5 

criteria. 

1. The Building Emission Rate 

(BER) is not greater than the 

Target Emission Rate (TER) 


building fabric and fixed 

services are no worse than set 

design limits 

3. Those parts of the building 

that are not provided with 

comfort cooling systems have 

appropriate passive control 

measures to limit the effect of 

solar gains 

4. The performance of the “as 

built” building is consistent 

with the BER 

5. Necessary provisions for 

energy efficient operation of 

the building are put in place. 

(Methodology document – 

NCM/SBEM (Simplified Building 

Energy Model). 

Table 28: Performance U-values for use in the notional building L2A 

Element U-value (W/m 2 K) 

Pitched roof 0.16 

Flat roof 0.25 

Walls 0.35 

Floors 0.25 

Windows and doors 2.20 

Display windows 6.00 

Smoke vents 6.00 

Vehicle access doors 1.50 

Air permeability and pressure 

testing: Non Dwellings L2A 

All new buildings require 

pressure testing. Exceptions are: 

• Building with a floor area less 

than 500m 2 . (Providing the air 

permeability of 15m 3 /(h.m 2 ) @ 

50Pa is used in the BER 

calculation and improvements 

to other areas of the 

building fabric and services 

to ensure the BER is no worse 

than the TER.) 

• Large complex building. (Refer 

AD L2A paragraph 72). 

27 



Work On Existing 

Buildings 

Dwellings L1B and 

Non-Dwellings L2B 

Demonstrating compliance on 

existing buildings with both 

these documents are similar and 

cover the following areas of 

work. 

• Extensions to buildings 

• Material change of use 

• Material alterations 

• Renovation of thermal 

elements. 

Extension work: L1B and L2B 

Building fabric standards 

New elemental U-value standards 

have been set for extension work 

to buildings (see Table 6). 

Achieving these fabric standards 

is one means of showing 

compliance with L1B and L2B. 

Other limiting criteria include: 

• Heating and hot water systems 

• Area of windows and doors 

• Insulation of pipes, ducts etc 

• Mechanical ventilation and 

cooling 

• Lighting (internal and external) 

• Reducing unwanted air 

leakage using Accredited 

Details – but no air 

permeability testing required 

Table 29: Standards for newly constructed elements 

Element Dwellings Other buildings 

U-value (W/m 2 K) U-value (W/m2K) 

Walls 0.30 0.30 

Floors 0.22 0.22 

Roof insulation at ceiling level 0.16 0.16 

Roofs insulation at rafter level 0.20 0.20 

Roofs (flat) 0.20 0.20 

Windows, roof windows & rooflights 1.80 1.80 

Doors with more than 50% of internal face glazed 2.20 2.20 

(Pedestrian) 

Other doors 3.00 - 

Entrance doors - 6.00 

Vehicle access or similar large doors - 1.50 

Roof ventilators (including smoke ventilators) - 6.00 

Note 

(For extension work to buildings other than dwellings L2B: Where the proposed extension has a total floor area greater than 

100m 2 and greater than 25% of the floor area of the existing building, it should be regarded as a new building and must 

comply with L2A using SBEM methodology) 

28 



Renovation and 

Repair Work: L1B 

and L2B 

Table 30: Standards for retained elements 

Element Dwellings Other buildings 

U-value (W/m 2 K) U-value (W/m 2 K) 

Walls 0.35 0.35 

Floor 0.25 0.25 

Roof insulation at ceiling level 0.16 0.16 

Roofs insulation at rafter level 0.20 0.20 

Roofs (flat) 0.25 0.25 

Windows, roof windows & rooflights 1.80 1.80 

Doors with more than 50% of internal face glazed 2.20 2.20 

(Pedestrian) 

Other doors 3.00 - 

Entrance doors - 6.00 

Vehicle access or similar large doors - 1.50 

Roof ventilators (inc smoke extract) - 6.00 

Note 

Where more than 25% of the surface area is being renovated, then the whole element should be upgraded to meet the 

thermal performance shown in Table 30 above 

Flexible measures 

If upgrade is not technically or 

functionally feasible or would 

not achieve a simple payback 

within 15 years, then upgrade to 

achieve best practical standards 

within the simple payback term. 

(Table A1 in AD L1B sets out the 

circumstances for cost-effective 

U-value targets when 

undertaking renovation work). 

Upgrading Retained Thermal 

Elements: L1B and L2B 

For further guidance refer to the 

appropriate Approved Document. 

29 

www.topblock.co.uk

Design Insulation manufacturers 

Tarmac Topblock products are 

compatible with a range of 

insulation materials commonly 

available for use as full fill, 

partial fill and internal or 

external insulation systems. 

Celotex 

Celotex Ltd 

Lady Lane Industrial Estate 

Hadleigh 

Ipswich 

Suffolk IP7 6BA 

Tel: 01473 822093 

Dritherm 

and Polyfoam 

Floorboard 

Knauf Insulation Ltd 

PO Box 10 

Stafford Road 

St Helens 

Merseyside WA10 3NS 

Tel: 01744 693885 


Dow Construction Products Ltd 

2 Heathrow Boulevard 

284 Bath Road 

West Drayton 

Middlesex UB7 ODQ 

Tel: 020 8917 5050 

The U-values given in this 

brochure are correct at the time 

of going to press and are based 

on manufacturers’ literature 

available at that time. 

Jablite 

Vencel Resil Ltd 

Infinity House 

Anderson Way 

Belvedere 

Kent DA17 6BG 

Tel: 020 8320 9100 

Kingspan 

Kingspan Insulation Ltd 

Shobdon Industrial Estate 

Pembridge 

Leominster 

Herefordshire 

HR6 9LA 

Tel: 0870 850 8555 

Rockwool 

Rockwool Ltd 

Pencoed 

Bridgend CF35 6NY 

Tel: 01656 862621 

Thermal Laminates 

British Gypsum Ltd 

East Leake 

Loughborough 

Leicestershire LE12 6JT 

Tel: 08705 456123 


Design Acoustic insulation 

General 

This information demonstrates 

how Tarmac Topblock products 

can be used to meet the 

requirements for sound 

insulation specified in Approved 

Document E (2003 Edition) of 

the Building Regulations for 

England and Wales. It includes 

Tarmac Topblock constructions 

that can be built as a Robust 

Detail, which is capable of 

providing enhanced sound 

insulation in houses and flats 

without the need for precompletion 

testing. 

The range of solutions presented 

is suitable for both housing and 

residential buildings. 

Compliance using 

Pre-Completion 

Testing 

Pre-Completion Testing (PCT) is a 

requirement permitted under 

Regulation 20A of the Building 

Regulations, to improve as-built 

compliance with the 

requirements of Part E1. 

PCT is not applicable to internal 

walls and floors. 

The normal frequency of testing 

on a site will be at least 1 in 10 

houses, flats or rooms for 

residential purposes. However, as 

building control will ask for one 

set of tests to be carried out 

between the first properties 

scheduled for completion, a site 

comprising only one pair of 

properties will therefore require 

a test to be completed. 

Where there are significant 

differences in construction, the 

testing regime will include 1 in 

10 of each type. For instance, 

houses including bungalows, 

flats and rooms for residential 

purposes should be grouped 

separately. Similarly sub-groups 

should be formed where there 

are variations in the construction 

of separating floors and walls, as 

well as any significant 

differences in the flanking 

construction. 

Sound tests are normally carried 

out at the developers or builders 

expense. 

Testing should be carried out 

when rooms on either side of 

the separating floor or wall are 

completed, but prior to 

decoration. Testing should not 

normally be carried out between 

living spaces and corridors, 

stairwells or hallways. 

Approved Document E advises 

that testing organisations with 

UKAS accreditation should 

preferably carry out testing. Such 

companies are listed on the 

UKAS web site: www.ukas.org. 

Members of The Association of 

Noise Consultants (ANC) are also 

regarded as suitably qualified to 

undertake pre-completion 

testing. Registered organisations 

are listed on the ANC web site: 

www.association-of-noise 

consultants.co.uk. 

Compliance using 

Robust Details 

As an alternative to compliance 

by PCT, for new homes, Robust 

Details (RD) has been established 

for a number of separating wall 

and floor constructions. These 

constructions have been 

rigorously field tested to 

demonstrate that they can 

consistently provide a 

performance better than the 

standard set by Approved 

Document E. Therefore, if built 

correctly they should provide a 

high level of sound insulation 

and consequently do not require 

routine testing. 

A handbook “Robust Details Part 

E, Resistance to the Passage of 

Sound” gives detailed guidance 

on the separating construction 

and the associated flanking 

elements. Each RD contains a 

“checklist” which can be 

reproduced and completed as a 

site record. Every new home 

built to the RDs will need to be 

registered with Robust Details 

Ltd and a plot registration fee 

paid. Further information on the 

scheme is available on their 

website: www.robustdetails.com 

There are currently 8 RD’s 

separating wall constructions 

featuring concrete blockwork, 

these consist of two leaves of 

blockwork with a 75mm 

(minimum) cavity - as shown in 

Figures 6 and 7. This choice of 

constructions allows virtually any 

type of concrete block (600- 

2300kg/m 3 ) from the Topblock 

range to be used. 



To many builders the adoption 

of RDs will mean little or no 

change to building practice, 

particularly if walls are to be 

plastered. Separating walls can 

also be finished with drylining, 

although it is stipulated that a 

8mm scratched finish render coat 

is first applied to the face of the 

blockwork. However, RD E-WM-8 

does allow directly applied 

drylining providing a proprietary 

mineral wool batt is used in the 

cavity. 

To avoid PCT completely, in flats, 

it is necessary to specify RD 

constructions to both the 

separating floor and wall. 

However, there may be 

circumstances where it is 

desirable to specify RD 

construction to either the floor 

or the wall. In such circumstances 

this is provided for, by requiring 

the non-robust detail element to 

be subject to PCT. However, 

designers must ensure that any 

non-robust detail construction is 

capable of meeting the required 

level of performance. 

Performance 

standards 

To meet the performance 

requirements for separating 

walls and floors, and for certain 

internal walls and intermediate 

floors, the specified levels of 

sound insulation in Table 32 

should be met. 

Achieving the specified 

performance is highly dependent 

upon good detailing, design and 

workmanship in separating walls 

and floors and also in the 

associated flanking construction. 

Masonry separating wall 

Ground floor not continuous between dwellings 

225mm (min) 

Foundation 

Fig 7. Ground floor junction with separating wall 

Plaster or drylining depending on block density 

Block density range 600-2300 kg/m 3 

Minimum 75mm cavity 

Block thickness 100mm minimum to each leaf 

Fig 6. Basic construction of Robust Details for masonry 

Table 31: Robust Details for masonry construction 

Robust Detail Basic Construction 

E-WM-1 

E-WM-2 

E-WM-3 

E-WM-4 

E-WM-6 

E-WM-7 

E-WM-8 

Masonry – dense aggregate blockwork (wet plaster) 

Masonry – lightweight aggregate blockwork (wet plaster) 

Masonry – dense aggregate blockwork (render and gypsum-based board) 

Masonry – lightweight aggregate blockwork (render and gypsum-based board) 

Masonry – aircrete blockwork (render and gypsum-based board) 

Masonry – aircrete thin-joint blockwork (render and gypsum-based board) 

Masonry – lightweight aggregate blockwork British-gypsum-Isover ISOWOOL 

(gypsum-based board) 

32 

www.topblock.co.uk


Table 32: Approved Document E (2003 Edition) performance requirements 

Element Performance requirement Solutions 

Airborne Impact 

Dwellings: New Build 

Separating Walls min 45dB Use either an RD with no requirement 

D nT,w +C tr for pre-completion testing – See Table 33 – 

or any other solution which will require 

pre-completion testing – See Table 34 

Separating Floors min 45dB max 62dB Consult Tarmac Topfloor for details 

D nT,w +C tr L' nT,w 

Internal Walls 1 min 40dB Use prescriptive solutions from Approved 

and 

R w 

Document E or lab-tested constructions (no 

Internal Floors 

Rooms for Residential Purposes 2 : New Build 

requirement for pre-completion testing): 

See Table 36 

Separating Walls min 43dB Use any solution which will require 

D nT,w +C tr pre-completion testing: See Table 37 

Separating Floors min 45dB max 62dB Consult Tarmac Topfloor for details 

D nT,w +C tr L' nT,w 

Internal Walls 1 min 40dB Use prescriptive solutions from Approved 

and R w Document E or lab-tested constructions (no 


Schools: New Build 

Internal Walls Consult Building Bulletin 93 

Internal Floors Consult Building Bulletin 93 

requirement for pre-completion testing): 

See Table 36 

Terminology 

Notes 

dB The unit used for many acoustic quantities to indicate the level with respect to a reference level. 

D nT,w +C tr Site measurement of airborne sound insulation with low-frequency correction factor (C tr ) applied 

(higher figure = better performance) 

L’ nT,w Site measurement for impact sound level (lower figure = better performance) 

R w Laboratory-derived measurement of airborne sound insulation (higher figure = better performance) 

1 This refers to walls between a bedroom or a room containing a w/c and other room and the internal floor 

2 

Rooms for residential purposes means a room, or a suite of rooms (not including a dwelling house or flat), which 

is occupied by one or more persons to live or sleep in but not including rooms in hospitals, or similar 

establishments, used for patient care 

Construction 

solutions 

An extensive range of solutions 

for new build construction are 

given in Tables 33 to 36. These 

cover constructions using the 

range of Tarmac Topblock 

products in separating walls, 

internal walls and beam and 

block internal floors. The 

solutions presented are by no 

means exhaustive and the 

Technical Services Department 

will be pleased to discuss the 

suitability of any construction 

not featured. 

The solutions provided are 

based, where appropriate, on 

the guidance published in 

Approved Document E, The 

Robust Details Handbook, 

together with sound tests 

commissioned by Tarmac 

Topblock. 

33 



Table 33: New Dwellings – Robust Details 

Construction Methods of compliance RD ref Recommended solution 

elements 

Separating walls Robust Details E-WM-1 

Pre-completion testing or 

not required 

E-WM-2 

13mm plaster (10kg/m 2 min) 

• 2 x 100mm Topcrete Standard E-WM-1 

• 2 x 100mm Hemelite Standard E-WM-2 

75mm min cavity 

E-WM-3 

or 

E-WM-4 

Drylining (8kg/m 2 min) 

Nominal 8mm 

parging 

• 2 x 100mm Topcrete Standard E-WM-3 

• 2 x 100mm Hemelite Standard E-WM-4 


E-WM-6 


• 2 x 100mm Durox Supabloc 4 or Supabloc 7 

• 2 x 100mm Toplite Standard or Toplite 7 

Nominal 8mm 

parging 


E-WM-7 


• 2 x 100mm* Durox System 600 or 700 

Nominal 8mm 

parging 

75mm min cavity - un-tied 

E-WM-8 


RD - no site 

testing 

required 

• 2 x 100mm Hemelite Standard 

35mm Isowool 

Hi-Therm RD35 

acoustic batt 

Notes 

1. Durox System 600 and 700 is thin jointed blockwork using a 2-3mm bed joint 

2. All Hemelite and Topcrete should be specified as solid blocks in accordance with BS EN 771-3 

3. The status of all the RD’s should be periodically checked with RD Ltd 

34 



Table 34: New Dwellings – Pre-completion testing 

Construction Methods of compliance Recommended solution 

elements 

Separating walls 

Constructions requiring pre-completion 

testing in accordance with Approved 

Document E or other technical guidance 

e.g. BBA certification or field test data 


• 215mm Topcrete Standard 

(100mm blocks laid flat) 

215mm min 


• 2 x 100mm Topcrete Standard 



• 2 x 100mm Hemelite Standard 


Site testing 

required 

• 2 x Durox Supabloc 4 or 7 

• 2 x 100mm Toplite Standard or 7 

• 2 x 100mm Durox System 600 or 700 


13mm plaster (10kg/m 2 min) or plasterboard drylining on an 8mm parge coat 

Notes 

1. Durox System is thin jointed blockwork using a 2-3mm bed joint 2. All Hemelite and Topcrete should be specified as solid blocks in accordance 

with BS EN 771-3 3. Where there is a step or stagger of at least 300mm in the Hemelite separating wall a drylined finish may be used. 

Aircrete 

separating walls 

The Robust Detail testing 

programme that established 

aircrete separating wall 

specifications demonstrated that 

these constructions performed as 

well as higher density aggregate 

block constructions. As a result 

of this Table 3 of the Robust 

Details handbook allows 

Durox/Toplite cavity separating 

walls to be used in combination 

with the separating floor 

constructions E-FC-1 and E-FC-4. 

This indicates that Aircrete blocks 

can be used in both the flanking 

and separating walls, thereby 

35 

gaining the twin benefits of 

excellent thermal and sound 

insulation. When using these 

options, however, the floor will 

be subject to pre-completion testing. 

Work continues in developing 

additional Durox/Toplite 

specifications through the 

Robust Details programme and it 

is advisable to refer to Topblock 

Technical Services or our website 

www.topblock.co.uk for the 

most up-to-date specifications. 

Table 35: Durox/Toplite separating & flanking walls in flats 

Note 

RD ref No 

E-WM-6 

(Conventional 

mortar) 

E-WM-7 

(Thin layer mortar) 

Robust Detail 

Separating Wall 

Durox/Toplite Blocks 

2 x 100mm with 

75mm cavity 

Supabloc 4, 7 & 10 

Toplite Standard 

Toplite ‘7’ 

Durox System 

600 & 700 

Flanking wall 

Durox/Toplite 

inner leaf 

100mm min 

Supabloc, Supabloc 4, 

7 & 10, Toplite GTI, 

Standard Toplite ‘7’ 

Durox System 

500, 600 & 700 

*In accordance with Table 3 of the Robust Details handbook these separating 

floors require pre-completion testing 

www.topblock.co.uk 

Robust Detail 

separating floor* 

RD ref No 

E-FC- 1 and 4 

E-FC- 1 and 4


Table 36: New Build Dwellings and Extensions 


elements 

Internal Walls 

Approved Document ‘E’ 

prescriptive solutions, or 

Tarmac Topblock 

constructions which have 

been shown by testing 

to meet the regulations 

Plaster or Drylining 

Wall blocks comprising 

• 100mm Durox Supabloc 

• 100mm Durox Supabloc 4 or 7 

• 100mm Toplite GTI 

• 100mm Toplite Standard or 7 

• 100mm Durox System 500/600 

Plaster or Drylining 

Wall blocks comprising 

• 100mm Hemelite Standard 

• 75mm Topcrete Standard 


Notes 

Approved Document ‘E’ 

prescriptive solutions, or 

Tarmac Topblock 

constructions which have 

been shown by testing 

to meet the regulations 

50mm min sand/cement screed 

Any ceiling finish 

1. Durox System 500/600 is thin jointed blockwork using a 2-3mm bed joint. 2. Solid Hemelite blocks should be used 

Infill blocks comprising 

• 100mm Durox Floor 

• 100mm Toplite Floor 

• 100mm Hemelite Standard 

No site testing 

required 

Table 37: New Build Rooms for Residential Purposes* 

Any of the recommended solutions shown for the New Build Dwellings (Tables 33 and 34) can be specified for separating 

walls for use in rooms for residential purposes. In addition, the solutions shown below may be used: 


elements 

Separating Walls Constructions requiring 

pre-completion testing in 

accordance with Approved 

Document E, or other 

technical guidance 

e.g. BBA certification or 

field test data 

215mm 

13mm plaster or drylining (10kg/m 2 min) 

• 215mm Durox Supabloc 4 or 7 plastered 

• 215mm Durox System 600 or 700 plastered 

• 215mm Toplite Standard or Toplite 7 plastered 

• 215mm Topcrete (100mm blocks laid flat) plastered 

or drylined 

13mm plaster or drylining (10kg/m 2 min) 

140mm 

190mm 

190mm Topcrete RPW 

Site testing 

required 

Note 

*Rooms for residential purposes include hotels, hostels, boarding houses, halls of residence and residential houses but exclude hospitals or similar 

establishments used for patient accommodation 

36 



Minimising flanking 

sound transmission 

Flanking sound transmission 

occurs indirectly via paths such as 

windows, external walls, ceilings 

and internal corridors. It is 

defined as sound transferred 

from a source room but not via a 

single common building 

element. It is essential that 

flanking transmission is 

considered at the design stage 

and that the construction 

detailing specified will minimise 

the effect on the overall acoustic 

performance. 

Typical solutions for key 

junctions with the separating 

wall are shown. Where a 

variation or a different solution 

applies to a Robust Detail, the 

text is suitably highlighted. 

Cavity and solid 

separating walls 

Fig 8. External cavity wall with 

blockwork inner leaf 

Fig 9. External cavity wall with 

blockwork inner leaf - stagger 

At least 

300mm 

Inner 

leaf 

The junction of the inner leaf of 

an external cavity wall and a 

cavity or solid separating wall 

Inner leaf of 

should be formed as follows: cavity wall 

• The external wall cavity should 

be stopped with a flexible closer 

at the junction with the 

separating wall (see Figs 8 and 

9), unless the cavity is fully filled 

using polystyrene beads or 

mineral wool 

Cavity stop 

Cavity 

separating 

wall 

External leaf 

Inner leaf 

Cavity stop 

Cavity separating wall 

Fig 10. Junction of solid separating 

wall and inner leaf of cavity wall 

Solid separating wall 

• The separating wall should be 

connected to the inner leaf by 

block bonding or a tied junction. 

Where structural considerations 

allow, the use of a tied junction 

is recommended, as it is likely to 

improve the acoustic 

performance (see Figs 10 and 11) 

• Where there is a separating 

floor, which is subject to precompletion 

testing, the mass of 

the inner leaf should be at least 

120kg/m 2 . Hemelite and 

Topcrete products can meet this 

requirement using a minimum 

inner leaf width of 100mm. 

Alternatively Durox Supabloc 7 

or Toplite ‘7’ blocks of minimum 

150mm width can be used (see 

Table 38). 

Fig 11. Junction of cavity separating 

wall and inner leaf of cavity wall 

i. Bonded junction i. Bonded junction 

Inner leaf of 

cavity wall 


Inner leaf of 

cavity wall 

Inner leaf of 

cavity wall 



ii. Tied junction 

ii. Tied junction 

Note 

The outer leaf and cavity insulation has been omitted in Figs 10 and 11 for clarity 

37 



Flanking walls 

Construction of flanking walls, 

given in Approved Document E, is 

dependent on the construction of 

the separating wall and floor and in 

some cases the position and size of 

openings adjacent to the party wall, 

see Table 38. However, other 

constructions may be suitable. 

Solutions 

Correct specification of flanking walls 

is essential to enable the separating 

walls and floors to fulfil their 

function. Select flanking walls from 

Table 38, for use in conjunction with 

or without separating floors. They 

are suitable for buildings that are 

subject to pre-completion testing, 

and are intended to complement the 

separating elements in meeting the 

performance standards for new 

build dwellings. 

Fig 12. Window positions for solid 

separating wall with aircrete inner leaf 

Not less 

than 1m 

high 

Durox or Toplite flanking wall 

Table 38: Tarmac Topblock flanking wall constructions for pre-completion testing 

Separating Construction of inner leaf 1 Housing Flats Comments 

wall type adjoining separating wall ie with a separating floor 

Note 

Windows should be located on 

both sides of the separating wall 

and on all storeys 

Not more than 700mm 

from the separating wall 

Separating 

wall - 100mm 

Topcrete laid 

flat 

Solid - Topcrete 

215mm 

100mm Durox - any grade 2 

100mm Toplite - any grade 

✓ 

✓ 

- 

- 

Windows required on 

both sides of the 

separating wall - see Fig 12 

150mm Toplite 7 

100mm Hemelite Standard 

✓ 

✓ 

✓ 

✓ 

Achieves 120kg/m 2 

wall weight 

100mm Topcrete Standard 

✓ 

✓ 

Cavity - Topcrete 

50mm 



✓ 

✓ 

- 

- 



✓ 

✓ 

✓ 

✓ 


wall weight 


✓ 

✓ 

Cavity - Hemelite 

75mm 



✓ 

✓ 

- 

- 

In accordance with 

BBA certificate 3 




✓ 

✓ 

✓ 

✓ 

✓ 

✓ 


wall weight 

Cavity - Durox Supabloc 4 


or 7 or Toplite Standard or 7 


75mm 

✓ 

✓ 

- 

- 

In accordance with 

BBA certificate 3 

150mm Toplite 



✓ 

✓ 

✓ 

✓ 

✓ 

✓ 


wall weight 

Notes 

1. All flanking constructions can be finished with plaster or plasterboard on dabs (10kg/m 2 min) 

2. If Durox Supabloc 400 is specified the minimum thickness should be 115mm 

3. The BBA has assessed these constructions and has confirmed that they may be used with aircrete separating walls with or 

without a step and/or stagger - refer to Technical Services for details 

38 

www.topblock.co.uk


Further details on acoustic 

performance are given in the 

respective BBA Certificates for 

Durox and Toplite products. 

RD solution 

No restrictions are specified 

regarding the positioning of 

openings in the flanking wall. 

The construction of the inner 

leaf of the flanking wall is 

summarised in Table 39. 

At the time of publishing there 

is not a solid wall Robust Detail 

solution, therefore the flanking 

construction guidance is based 

on Approved Document E and 

BBA Certificates held for certain 

Tarmac Topblock products. 

Table 39: Tarmac Topblock flanking constructions for RDs 

Separating Robust Construction of inner leaf 1 Housing Flats 

wall type Detail ref adjoining separating wall 

Cavity - Topcrete 

75mm 

E-WM-1 

or 



✓ 

✓ 

E-WM-3 


✓ 

✓ 


✓ 

✓ 

Cavity - Hemelite 

75mm 

E-WM-2 

or 



✓ 

✓ 

E-WM-4 

or 

E-WM-8 5 



✓ 

✓ 

✓ 

✓ 

Cavity - Durox Supabloc 4 or 7 

or Toplite Standard or 7 

75mm 

E-WM-6 



✓ 

✓ 

✓ 4 

✓ 4 



✓ 

✓ 

Cavity - Durox System 600 or 700 

75mm 

E-WM-7 3 

100mm Durox System 500 


✓ 

✓ 


✓ 

Notes 

1. All flanking constructions can be finished with plaster (10kg/m 2 min) or plasterboard (8.0kg/m 2 min) on dabs 

2. If Durox Supabloc 400 is specified the minimum thickness should be 115mm 

3. Used in conjunction with 2-3mm thin joint mortar joints in both the separating and flanking walls 

4. If used in conjunction with robust detail separating floors, then the separating floor will be subject to a pre-completion testing 

5. Separating wall includes a 35mm Isowool Hi-Therm RD35 

39 



Junction with timber floors 

• Generally Approved Document E 

requires that if floor joists are 

to be supported on the 

separating wall, then they 

should be supported on 

hangers. However some 

practical difficulties with using 

hangers have already been 

acknowledged, particularly as a 

result of the changes to 

Approved Document L 

Fig 13. Timber floor 

Hanger 

Hanger 



• In situations where it is 

genuinely unavoidable to build 

joists into separating walls, it is 

recommended that Building 

Regulation approval is sought 

prior to commencing on site. In 

these situations it would be 

advisable to follow the 

guidance given in the Robust 

Details. 

Fig 14. External cavity wall at 

eaves level 

Flexible 

closer 

RD Solution 

As an alternative, when using an 

RD solution, floor joists may be 

built in provided that the 

following details are observed: 

For solid timber joists, the 

mortar joints around each joist 

perimeter should be recessed or 

struck (pressed in at the lower 

edges) and the joint between 

the blockwork and the timber 

should be carefully pointed with 

silicone sealant. The sealant 

should be applied after the 

building is weatherproofed so 

that the blockwork and joists are 

reasonably dry. 

If timber-engineered joists are 

used, they should be fitted with 

proprietary filler pieces fitted on 

both sides of the web between 

the top and bottom flanges. The 

depth of the filler pieces should 

be slightly less than the dimension 

between the joist flanges to 

achieve a loose fit. All joints and 

air gaps should be pointed with 

silicone sealant as detailed 

above. Alternatively, proprietary 

joist cap-ends may be used. 

In either case the joists must not 

be continuous between dwellings 

and if the wall finish is drylining, 

the pre-requisite render coat 

need not be carried into the 

floor zone. 

Junction with concrete floors 

• Concrete floors should 

generally be built into the 

separating wall and, in the case 

of a cavity wall, carried 

through to the cavity face of 

the leaf. When concrete floors 

are used at ground floor, they 

should not be continuous 

under a cavity separating wall. 

Junction with ceiling and roof 

• The separating wall should be 

continuous to the underside of 

the roof 

• The junction between the 

separating wall and roof 

should be filled with a flexible 

closer which is also suitable as 

a fire stop. Similarly the 

external wall should be closed 

at eaves level with a suitable 

flexible material such as 

mineral wool (see Fig 14). 

Wall ties 

• Wall ties to connect the 

separating wall leaves should 

be 'Type A' butterfly pattern 

(or ties of equivalent acoustic 

performance). 

Electric Sockets 

The position of sockets on 

opposite sides of the separating 

wall should be staggered. 

Flue blocks 

Flue blocks should be specified 

that do not adversely affect the 

sound insulation. A suitable 

finish must be used over the 

flue blocks. If in doubt refer 

to BS 1289-1:1986 and seek 

manufacturer’s advice. 

RD solution 

Specific guidance is given for 

allowing flue blocks to be used 

providing they are staggered 

along the separating wall – refer 

to the individual RD for detail. 

Separating floors 

We recommend that Tarmac 

Topfloor Limited is contacted for 

advice on the specification of 

precast concrete floors to comply 

with Building Regulations: 

Tel 01332 360601 

Fax 01332 868401 

40 



Building layout - 

houses/flats 

• When designing dwellings it is 

preferable that rooms of 

similar use should be located 

adjacent to each other across 

the separating wall 

• Reducing the common areas 

of walls and floors can result 

in improved sound insulation. 

This can be achieved by the 

use of steps and staggers 

Fig 15. Introducing steps and 

staggers to improve acoustic 

design 

Staggers 

Steps 

• Good design should ensure 

that bedrooms of one flat are 

directly below the bedrooms 

of the flat above 

• Services such as refuse chutes, 

vertical ducts and lifts should 

not adjoin bedrooms or 

living rooms 

• Movement joints should be 

avoided in separating walls 

• Mechanical equipment (such 

as boilers and cooker hoods) 

should never be mounted on a 

separating wall, unless secured 

on acoustic mountings. 

Building layout - 

residential 

accommodation 

(hotels, nursing and student 

accommodation etc.) 

The construction for the 

separating wall should also be 

specified for the corridor wall in 

order to control flanking 

transmission and to provide the 

required sound insulation 

between the residential room 

and the corridor. 

It is essential that any door has 

good perimeter sealing 

(including the threshold where 

practical) and have a minimum 

mass of 25 kg/m 2 . Alternatively, a 

doorset may be used, providing 

it achieves a minimum sound 

reduction index, Rw, of 29dB 

(based on laboratory 

measurements to BS EN ISO 140-3). 

It is also helpful to design the 

room layout to maximise the 

distance between adjacent doors. 

Noisy parts of the building (e.g. 

function rooms, bars) should 

preferably have a lobby, double 

doors or a high-performance 

doorset to contain the noise. 

Where this is not possible, 

nearby rooms for residential 

purposes should have similar 

protection. 

Particular attention should be 

paid to the specification of doors 

along corridors in multioccupancy 

buildings. 

41 

www.topblock.co.uk

Design Durability 

General 

The complete range of Tarmac 

Topblock products is inherently 

durable and is suitable for a 

variety of exposure conditions. 

The guidance presented includes 

recommendations for the use of 

products to resist frost, moisture, 

and sulfate attack. 

Frost resistance 

Extensive use of Tarmac Topblock 

products has confirmed their 

ability to achieve good frost 

resistance in practice, making 

them ideal for use below dampproof 

course (DPC) level. 

Generally products will be 

selected on the basis of the 

recommendations of 

BS 5628-3. 

In addition, the assessment 

procedure for BBA Certificates 

covering Durox and Toplite 

aircrete blocks includes tests to 

confirm the resistance of these 

blocks to the freeze/thaw 

conditions likely to occur below 

DPC. The ‘Code of Best Practice 

for the use of Aircrete Products’ 

also confirms their suitability. 

There is little or no risk of frost 

attack when blocks are used: 

• internally, above or below DPC 

• externally, above DPC when 

walls are protected by cladding 

or render. 

Any Topblock product is suitable 

for use in the above situations. 

For guidance on the selection 

of blocks for other applications, 

such as in unprotected walls 

above DPC, free-standing walls, 

and parapets, refer to 

BS 5628-3 or contact our 

Technical Services Department. 

The mortar properties should be 

appropriate to the degree of 

frost resistance required. 

42 



DPC 

Resistance 

to moisture 

Moisture in block walls does not 

adversely affect their strength. 

Provision must be made against 

rising damp by the introduction 

of DPCs at suitable locations. 

These will provide a barrier to 

the passage of water from the 

exterior of the building to the 

interior, or from the ground to 

the structure. 

In every external wall, a 

horizontal DPC should be 

provided at least 150mm above 

the finished level of the external 

ground or paving. To prevent 

the transfer of moisture from 

external walls into solid floors, 

the damp proof membrane in 

the floor, and the DPC in the 

wall, should overlap a minimum 

of 100mm or be sealed. 

DPCs should not be bridged by 

rendering and should extend 

through the full thickness of the 

wall or leaf, and preferably 

project slightly beyond the 

external face. 

Insulation 

Screed 

Durox, Toplite, 

Hemelite or Topcrete 

Foundation 

Fig 16. Topblock Foundation blocks 

below DPC 

The external wall should be 

selected to resist the anticipated 

exposure conditions. This may be 

done in accordance with BS 8104 

‘Code of practice for assessing 

exposure of walls to wind-driven 

rain’. This will result in the 

determination of the local spell 

index that will allow the 

designer to select an appropriate 

construction. To provide 

adequate resistance to rain 

penetration, the specification, 

design, detailing and 

construction of the total wall 

element should take account of 

local exposure conditions. 

Guidance on the resistance to 

rain penetration of solid and 

cavity wall construction is given 

in BS 5628-3. 

Sulfate resistance 

The environment below ground 

level should be assessed in 

accordance with BRE Special 

Digest 1, 'Concrete in aggressive 

ground'. 

There are five classes of sulfate 

level, DS-1 to DS-5, for soils and 

ground waters, with DS-1 having 

little or no sulfate and DS-5 

having high sulfate content. 

BRE Special Digest 1, Part 4: 

'Design guides for specific 

precast products' gives guidance 

on the specification of precast 

products for such conditions. 

Hemelite and Topcrete 

aggregate blocks 

In practice, aggregate blocks 

have been used below ground in 

all kinds of sulfate conditions for 

many years before a potential 

problem with sulfates was 

identified. 

Recent research 1 supports the 

long-term empirical evidence 

and suggests the guidance in 

BRE Special Digest 1 is too 

conservative. The research 

supports the BRE view that 

carbonation imparts sulfate 

resistance to concrete; aggregate 

blocks have a more open texture 

than concrete cast in-situ and are 

more able to surface carbonate. 

Further research 2 has 

demonstrated that the cement 

matrices of aggregate blocks and 

wet concrete mixes are very 

similar. These findings support 

and explain the high durability 

of aggregate blocks in terms of 

both frost and sulfate resistance. 

Durox and Toplite aircrete blocks 

The recommendations for use in 

sulfate soils are based on BRE 

Special Digest 1, Part 4, and are 

endorsed by the BBA Certificates 

covering Durox and Toplite 

aircrete. 

Notes: 1 Sulfate resistance of aggregate 

concrete blocks: Pettit G, Harrison W, 

Littleton I. Proceedings of the 15th 

International Congress of the Precast 

Concrete Industry July 1996 

2 Understanding the durability of 

aggregate concrete masonry units through 

a comparison of cement matrices of wet 

and semi-dry mix concrete: Pettit G, 

Harrison W. Proceedings of the 16th 

International Congress of the Precast 

Concrete Industry 1999 



Specification 

guidance 

When specifying blocks for sites 

where sulfates are present, 

always determine whether: 

• the conditions found relate to 

the depth at which the 

concrete units are to be used; 

relatively few sites have sulfate 

concentrations greater than 

DS-1 in the first metre of soil 

• ground water is likely to be 

present at the depths at which 

units are to be used; the risk of 

sulfate attack in dry conditions 

is minimal. 

The following recommendations 

are made on the basis of BRE 

Special Digest 1 and long-term 

research. 

Internally, above or below DPC: 

no risk of sulfate attack. 

Externally, above DPC, protected 

by render or cladding: 

no risk of sulfate attack. 

Externally, above DPC and 

unprotected by render or 

cladding: 

levels of sulfates in the 

atmosphere or precipitation are 

not usually sufficient to present 

a risk of sulfate attack for any 

Tarmac Topblock product. 

Externally, below DPC: 

Guidance on the use of Topblock 

products in class DS-1, DS-2 and 

DS-3 sulfate conditions is given 

in Table 40. 

Table 40: Use of Tarmac Topblock products in DS-1 to DS-3 

sulfate soil conditions 

DS-1 DS-2 DS-3 

Hemelite or Topcrete aggregate blocks 

Hemelite 3.6 N/mm 2 

✓ 

Hemelite 7.3 N/mm 2 ✓ ✓ ✓ 

Hemelite Foundation ✓ ✓ ✓ 

Topcrete Cellular 3.6 N/mm 2 ✓ ✓ ✓ 

Topcrete 7.3 N/mm 2 or greater ✓ ✓ ✓ 

Durox or Toplite aircrete blocks 

Durox Supabloc 400* 

✓ 

Durox Foundation ✓ ✓ 

Durox Supabloc ✓ ✓ 

Durox Supabloc 4 ✓ ✓ ✓ 

Durox Supabloc 7 ✓ ✓ ✓ 

Toplite GTI* 

✓ 

Toplite Foundation ✓ ✓ ✓ 

Toplite Standard ✓ ✓ ✓ 

Toplite ‘7’ ✓ ✓ ✓ 

Note *Suitable for use as the inner leaf of cavity walls and internal walls below DPC 


Design Movement control 

The causes of 

movement 

All buildings undergo small 

movements and dimensional 

changes from various causes; 

those which most affect 

concrete masonry are: 

• changes in moisture content 

of the blockwork (reversible) 

• changes in temperature 

(reversible) 

• carbonation of the concrete 

(non-reversible) 

• movement of the adjoining 

structure (reversible or 

non-reversible). 

There is a general tendency for 

concrete masonry to contract as 

it dries to equilibrium moisture 

content and the concrete 

carbonates. Clay masonry, by 

contrast, expands as the masonry 

matures and adsorbs water. 

Unless proper provision is made 

to allow such movements to take 

place in a controlled manner, 

cracking may occur; such 

cracking presents little hazard, 

but can be unsightly. The advice 

given here is based upon 

the recommendations of 

BS 5628-3 and long-term 

experience. 

Provision for 

movement 

The amount of movement to 

be expected is related to the 

moisture content of the materials, 

the ability of the masonry to 

carbonate after construction, and 

the ambient temperature during 

construction. Unless slip planes 

are provided, longitudinal 

movement in loadbearing 

masonry is likely to be less than 

that in non-loadbearing masonry 

because of the restraint provided 

by the structure. 

Whilst it is possible to calculate the 

likely level of movement and then 

to design for it, the number of 

variables involved make calculation 

complex; it is more usual to: 

• divide masonry into a series of 

discrete panels, separated by 

joints which allow movement 

of the panels, and/or 

• restrict movement by using bed 

joint reinforcement. 

Internal walls in single occupancy 

dwellings do not normally require 

movement joints; any small 

movement cracks are made good 

after the building has dried out. 

However, if the length of internal 

walls exceeds three times their 

height then provision for movement 

may need to be considered. 

Joints to accommodate 

horizontal movement 

Movement joints should be 

considered at the following 

locations: 

• at regular spacings in long runs 

of walling; 

• above and below openings; 

• at changes in wall height; 

• at changes in wall thickness; 

• at junctions with dissimilar 

materials; 

• to coincide with movement 

joints in other parts of the 

construction. 



Movement joints 

Movement joint spacings 

for Tarmac Topblock products in 

walling are given in Table 41. 

Where end restraint is provided, 

such as at bonded corners, the 

recommended spacings should 

be halved. Long, low panels – 

those with length to height 

ratios greater than 3:1 – should 

have joints at reduced spacings. 

In such cases, bed reinforcement 

may be a better solution as this 

will avoid an excessive number 

of movement joints. 

Table 41: Recommended 

movement joint spacings 

Product 

Joint spacing (m) 

Hemelite 7.0 - 8.0 

Topcrete 7.0 - 8.0 

Toplite 6.0 

Durox 6.0 

Formation of 

movement joints 

Typically, movement joints to 

accommodate horizontal 

movement should be straight, 

10mm wide butt joints built in as 

work proceeds. They should be 

filled with a suitable 

compressible material and sealed 

as required. Wider joints may be 

required where they pass 

through the whole structure. 

In some situations, for example 

internal walls, a simple butt joint 

may be used without filler. 

Suitable joint fillers include 

flexible cellular polyethylene, 

cellular polyurethane or foam 

rubber. Internal joints, which 

generally only need to allow for 

contraction, may be filled with 

fibreboard and carried through 

plasterwork. 

Structural continuity across 

movement joints, and at 

junctions of masonry with the 

structural frame, is achieved by 

using flat metal ties with one 

end de-bonded (for example by 

a plastic sleeve) at 450mm 

maximum vertical centres 

(see Fig 17). 

Movement joints must be 

continuous through applied rigid 

finishes such as plaster or render 

(see Fig 18). The use of a 

proprietary plaster/render stop 

bead will give the best results. 

Further construction details for 

movement joints are given in 

Figs 23 - 33. 

Flat section 

metal tie 

with one end 

de-bonded 

to alternate 

courses 

Joint 

filler 

Sealant where 

required 

Joint filler 

Sealant 

where 

required 

Fig 17. Movement joint with 

flat-strip metal ties 

Stop bead 

Fig 18. Movement joint continued 

through rigid finishes 



Vertical and 

lateral movement 

In non-loadbearing walls a gap, 

usually packed with soft filler, 

is left at the soffit to allow for 

vertical movement of the 

structure above. Lateral restraint 

can be provided by lengths of 

steel angle fixed to the soffit on 

either side of the masonry after 

the wall has been constructed 

(see Fig 19). Alternatively, sliding 

ties may be built into masonry 

perpend joints and fixed to the 

soffit; the use of ties which do 

not permit movement may cause 

dislodgement of the top course 

of masonry. 

Bed joint 

reinforcement 

Movement may also be 

controlled using prefabricated 

wire reinforcement in mortar 

bed joints to distribute stresses 

throughout the immediate area 

of the wall (see Fig 20). This will 

prevent major cracking. 

For use in conjunction with 

Durox System, thin joint block 

work, polymer movement 

control fabric, e.g. ‘Clanmesh’, 

can be considered as an 

alternative to steel composition 

reinforcement. Tests conducted 

by John Moores University have 

shown this material to be 

effective when incorporated in 

the bed joints to reduce the 

occurrence of shrinkage cracks 

and minimise crack width. 

Further details on application are 

given in the Durox System thin 

joint guide. 

Bed joint reinforcement may 

be used: 

• at stress concentrations around 

door and window openings 

(see Fig 21) 

• in long panels where 

movement joints are 

impractical (see Fig 22) 

• to increase the spacing of 

movement joints beyond 

that recommended for 

unreinforced masonry. 

Steel 

angle 

providing 

lateral 

support 

Soft filler 

Bed joint reinforcement 

Fig 21. Bed joint reinforcement at openings 


should extend a minimum 

of 600mm past opening 

Fig 19. Lateral restraint of 

non-loadbearing walls 

Reinforcement 


Fig 22. Bed joint reinforcement in low height panels 

Fig 20. Bed joint reinforcement 

47 

www.topblock.co.uk


Mortar 

A significant proportion of the 

overall shrinkage of masonry is 

owing to the mortar. The effect 

of the shrinkage can be reduced 

by ensuring mortar joints are 

weaker than the masonry units; 

this reduces the stresses by 

allowing redistribution of forces 

within the wall. However, the 

mortar must still be compatible 

with the strength and durability 

requirements of the masonry. 

Differential 

movement 

Differential movement may 

occur when designs combine 

materials with differing physical 

characteristics. This is not usually 

a problem when various types of 

concrete masonry are combined; 

for example only a small amount 

of differential movement will be 

produced between a Topcrete 

dense aggregate outer leaf and 

a Durox or Toplite inner leaf. 

However, allowance must be 

made for differential movement 

when concrete and clay masonry 

are used in adjoining leaves and 

the use of rigid wall ties should 

be avoided where possible. 

When concrete and clay units are 

built into the same panels, slip 

planes and/or more closely 

spaced movement joints may be 

necessary to allow for the 

differential movement. 

Site practice 

Protecting blocks from rain and 

snow will help minimise 

excessive movement caused as 

the blockwork dries out. 

Packs of blocks should be covered 

with weatherproof sheeting. 

Blocks can be supplied shrinkwrapped 

but these should also 

be covered once the wrapping has 

been opened. It is equally 

important to provide weather 

protection to blockwork under 

construction. Loaded-out blocks 

should be covered with a spot 

board and partially completed 

walls should be covered with a 

scaffold board or waterproof 

sheeting. 

During periods of very hot 

weather, blockwork should not 

be allowed to dry out too 

quickly. 

Summary 

• Internal walls in single 

occupancy dwellings do not 

normally require movement 

joints 

• Movement joints in 

unreinforced masonry should 

normally be 6.0 - 8.0m apart, 

depending on block type, for 

normal storey height walls 

• A movement joint should be 

provided at half the normal 

spacing where there is end 

restraint such as at bonded 

corners 

• Unrestrained or lightly loaded 

walls with length/height ratios 

greater than 3:1, such as low 

horizontal panels or parapet 

walls, require more frequent 

movement joints or the 

introduction of bed joint 

reinforcement 

• Bed joint reinforcement should 

be used to control movement 

at stress concentrations such as 

window and door openings, or 

to extend the spacing of 

movement joints 

• Where appropriate, suitable 

provision for movement should 

be allowed at the tops of walls 

• Over-strong mortars should 

be avoided 

• Suitable precautions should be 

taken when mixing materials 

of different compositions, such 

as clay and concrete, in the 

same wall. Movement joints 

and slip planes should be 

introduced as appropriate. 

48 



The following design details are 

the most common movement 

joint details likely to be 

encountered in the design of 

concrete blockwork. They are 

generally applicable to all 

Tarmac Topblock products but 

the designer is also referred to 

the Durox System guide for 

details of movement joints and 

bed joint reinforcement when 

designing with Durox thin 

joint blocks. 

Fig 24. Movement joints to walls 

incorporating hollow blocks 

Joint filler (and sealant 

where required) 

Voids filled 

with stiff 

mortar to 

support tie 

Flat section 

metal tie with 

one end debonded 

at 

450mm centres 

Fig 23. Movement joints to walls 

incorporating solid blocks 

Fig 25. Movement joints 

at an intersecting wall 

Joint filler 

(and sealant 

where required) 

Flat section metal 

tie with one end 

de-bonded at 

450mm centres 

Sealant where required 

Joint filler 

Flat section metal tie with 

one end de-bonded at 

450mm vertical centres 

10mm 

49 



Fig 26. Movement joint to the 

inner leaf of a cavity wall 

Fig 27. Movement joint at external 

wall junction to separating wall 

Wall ties at maximum 


Flat section metal tie with one 

end de-bonded at 450mm 

vertical centres 

Flat section metal tie with one 

end de-bonded at 450mm 



25mm clear 

Joint filler 

Joint filler 

225mm max 

225mm max 


MINIMUM 100mm 

EMBEDMENT 

225mm MAXIMUM 

Outer leaf 



Outer leaf 

Fig 28. Movement joint to a 

rendered outer leaf 

Fig 29. Movement joint and slip plane 

to the side of door openings 



Inner leaf 

Vertical movement 

joint continued up 

to top of wall 


tie with one end 

de-bonded at 450mm 


Movement joint 

225mm max 

225mm max 

Elevation 

Lintel 

Render 

Joint filler 

Render 

stop beads 

Lintel bearing bedded 

and jointed on DPC or 

two layers of DPM 

Joint filler 

Sealant 

50 

www.topblock.co.uk


Fig 30. Movement joint to 

blockwork at internal steel column 

Fig 31. Movement joint to blockwork 

supported by a steel frame 

Flexible ties at 

max 300mm 



Joint filler 75mm min 

Column 

225mm max. 

Fire protection 

to column 

Joint filler 


ties with de-bonding 

sleeves at 450mm 

vertical centres. 

Allow a minimum 

100mm embedment. 

Ties fixed to column 

(e.g. shot fired). 

Fire protection 

to column 

Column 

40mm min 



Outer leaf 

Fig 32. Movement joint to blockwork 

supported on a steel frame with internal pier 

Joint filler 

Sealant where 

required 

Fig 33. 

Movement joint at reinforced 

concrete column 

Flexible 

ties at max 

300mm 

vertical 

centres 

Concrete 

column 

Sealant where 

required 

Joint filler 

Dovetail channel 

cast into column 

Joint filler 

Concrete 

column 

Flat section 

metal ties 

with de-bonding 

sleeves at 450mm 

vertical centres. 

51 


Design Safe handling 

Regulations 

and guidance 

Increased awareness of Health 

and Safety issues has focused 

attention on building materials, 

including consideration of 

manual handling. The over-riding 

need is to ensure a safe 

environment and good working 

conditions for the construction 

team. 

Two items of legislation are 

relevant to the manual handling 

of blocks: 

• Manual Handling Operations 

Regulations (1992), placed 

duties on employers to carry 

out a risk assessment on all 

manual handling tasks 

• Construction (Design and 

Management) Regulations 

(1994), imposes mandatory 

Health and Safety requirements 

on clients, designers and 

contractors. 

Health and Safety Executive (HSE) 

Construction Sheet 37 ‘Handling 

Building Blocks’ gives guidance 

on meeting the requirements of 

those regulations. It advises there 

is a high risk of injury in the 

single-person repetitive handling 

of units heavier than 20kg. Units 

heavier than 20kg should be 

handled mechanically or by two 

man teams. 

Single-person handling of a small 

number of heavier units ,such as 

quoins and reveal blocks,is not 

identified as posing a high risk of 

injury. 

Guidance is also available in the 

CBA publication ‘Aggregate 

Concrete Blocks. Safe Handling 

and Correct Use’. 

Design 

considerations 

The extensive range of products 

from Topblock ensures the 

maximum choice possible in the 

specification of building blocks 

for any construction project. 


aggregate blocks 

It is possible to design with 

Hemelite and Topcrete aggregate 

blocks to satisfy the essential 

technical requirements for a 

project, using units meeting 

recommended handling 

guidelines. In some cases regular 

blocks can be laid flat, or 

constructed back to back, to 

achieve the required wall width. 

In other cases purpose designed 

blocks such as the Midi or RPW 

block can be specified safe in the 

knowledge that their design 

encompasses manual handling. 

Table 42: Aggregate blocks – Alternative to full width blocks exceeding 20kg 

Wall Width Material Block or Construction Solution 

140mm Hemelite 140mm Hemelite solid (3.6 or 7.3N/mm 2 ) 

140mm Hemelite cellular (3.6N/mm 2 only) 

Topcrete 140mm Topcrete Midi (7.3, 10.4, 17.5 or 22.5N/mm 2 ) 

140mm cellular, cellular Multicore or hollow (3.6 or 7.3N/mm 2 ) 

190mm Hemelite 190mm Hemelite cellular or hollow (3.6N/mm 2 only) 

190mm Hemelite Ultra solid (3.6 or 7.3N/mm 2 ) 

2x90mm Hemelite solid, collar jointed (3.6 or 7.3N/mm 2 ) 

Topcrete 

190mm Topcrete RPW (7.3N/mm 2 only) 

2x90mm Topcrete solid, collar jointed (7.3N/mm 2 only) 

215mm Hemelite 100mm Hemelite solid, units laid flat (3.6, 7.3 or 10.4N/mm 2 ) 

140mm Hemelite solid, units laid flat (3.6 or 7.3N/mm 2 ) 

2x100mm Hemelite solid, collar jointed (3.6, 7.3 or 10.4N/mm 2 ) 

Topcrete 100mm Topcrete solid, units laid flat (7.3, 10.4 or 22.5N/mm 2 ) 

2x100mm Topcrete solid, collar jointed (7.3, 10.4, 17.5 or 22.5N/mm 2 ) 

Notes 1) The availability of products should be checked with the Tarmac Topblock sales office. The above list is not exhaustive – 

please discuss your project requirements with our Technical Services team 

2) Refer to the product brochures for the technical specification of each product, or consult Technical Services for advice 

3) Wall constructions consisting of hollow blocks, cellular block, solid blocks laid flat or of collar jointed blockwork, will 

have a characteristic compressive strength slightly less than an equivalent thickness of wall built using solid blockwork 

(see pages 7-8). The use of these forms of construction should therefore be subject to the approval of the project engineer 

52 




aggregate blocks (continued) 

Table 42 provides the core 

solutions for using Hemelite and 

Topcrete, using units that fall 

within the guidance given in 

Construction Sheet 37. 

Using blocks in different aspect 

ratios will affect the characteristic 

compressive strength (fk) of the 

blockwork. To aid designers in 

their assessment values that are 

applicable to the entire range of 

Tarmac Topblock products is 

given in the Structural Design 

section of this Guide. 

Durox or Toplite aircrete blocks 

Aircrete is an inherently 

lightweight material which 

ensures that the majority of 

Durox and Toplite aircrete blocks 

in 75-215mm widths fall within 

the guidance for single-person 

repetitive handling. Foundation 

blocks are available in a range of 

widths from 260mm to 300mm. 

Some of these sizes at 215mm 

coursing height will exceed the 

nominal 20kg guidance. 

Foundation blocks with a 140mm 

bedding height are available and 

are recommended as a safer 

alternative. 

The designer should refer to the 

relevant product brochures for 

approximate unit weights of 

specific products. 

Health and Safety 

Full details of recommendations 

for the safe use of our products 

are given in the Tarmac Topblock 

Product Health and Safety Data 

Sheet. 

Site handling 

Handling by crane 

Do not lift packs of blocks over 

the workforce when using crane 

off-load vehicles and low level 

cranes. Packs to be raised by 

tower crane and high level crane 

should be netted or placed in 

cages before lifting. 

Packaging 

Tarmac Topblock offers a range 

of packaging options to suit 

individual site requirements. 

• Packs on pallets 

• Packs with voids for fork-lift 

handling (not available for 

Paint Quality products) 

• Packs for handling by grab. 

53 

www.topblock.co.uk


Site practice 

Good site practice requires 

planning and this is a 

management responsibility. 

By doing so the efficient and 

safe use of our products from 

receipt of delivery to installation 

should be ensured. 

The following points form part 

of best site practice: 

Site organisation: 

• Minimise manual handling by 

delivering units as close to the 

point of laying as safety 

considerations permit 

• Move blocks in packs and by 

mechanical means wherever 

possible 

• Store blocks on a clean, level 

and firm base 

• Avoid stacking blocks above 

head height, unless they are to 

be moved by mechanical 

means 

• Provide protective equipment – 

including safety helmets, safety 

footwear and suitable gloves – 

and ensure it is used 

• Ensure the blocklayer’s work 

area is clear of obstruction and 

properly organised. 

Block laying: 

• Use eye protection whilst 

cutting the banding on packs 

• Ensure blocks do not fall when 

packaging is removed 

• Load blocks out to above knee 

height 

• Handle blocks close to the 

body 

• Raise scaffolding to keep 

blockwork below shoulder 

height 

• Raise mortar spot boards to a 

convenient working height to 

avoid bending 

• Use eye protection and dust 

suppression or extraction 

measures when cutting or 

chasing blocks. 

54 


CI/SfB 

November 2006 

Ff4 

Where do I find more 

Tarmac Topblock offer a complete range of aircrete, lightweight and dense products. As a UK market leader you can 

expect our blocks to meet the most demanding of building regulations and requirements. To make contact could 

not be easier! 

National Sales Helpline 

Call us on: 0845 606 2468 

Technical Helpline 

Call us on: 0870 242 1489 

Email: technical.services@tarmac.co.uk 

Literature requests: 

Call us on: 08456 044 114 

Email: marketing@tarmac.co.uk 

Quote reference L106 

The product brochures available include: 

Durox - large format aircrete blocks 

Toplite - aircrete blocks 

Hemelite & Topcrete - lightweight & dense aggregate blocks 

Durox System - thin joint blocks 

Tarmac Topblock Limited 

Millfields Road 

Ettingshall 

Wolverhampton 

West Midlands WV4 6JP 

Website: www.topblock.co.uk 

Tarmac and the ‘T’ mark are registered trademarks of the Tarmac Group. 

Although Tarmac Limited does its best to ensure that any advice, recommendations or information it may give is accurate, no liability or responsibility of any kind (including liability for negligence) is 

accepted in this respect by Tarmac Limited, its staff or agents. Claims and statements made by Tarmac Limited regarding its products refer to those which have been properly handled on site. Tarmac 

Limited cannot accept any liability or responsibility of any kind (including liability for negligence) for problems caused by the acts or omissions of third parties or by poor practices.

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