Lisø PhD Dissertation Manuscript - NTNU

Concrete walls
32 %
LECA masonry
10 %
Other
3 %
Brick cavity or veneer
walls
17 %
Timber framework
30 %
Metal framework
7 %
Sandwichelements
1 %
Figure 5. Defect cases for the 10-year period 1993-2002 concerning
external walls above terrain, distributed by type of wall
(587 cases, 29% of the total amount of building defects).
Other
6 %
Element walls under
terrain
7 %
Concrete walls
66 %
Brick walls
1 %
LECA masonry
20 %
Figure 6. Defect cases for the 10-year period 1993-2002 concerning
external walls under terrain, distributed by type of wall
(145 cases, 7% of the total amount of building defects).
Pitched wooden roof with
cold attic
12 %
Raised wooden roof structure
on a underlay of concrete or
ligthweight concrete
2 %
Insulated pitched wooden
roof with combined wind
barrier and sheathing
(watertight breather
membrane)
7 %
Insulated pitched wooden
roof with separate wind
barrier and sheathing
(venting (air gap) between
wind barrier and sheathing)
7 %
Other
11 %
Pitched wooden roof with
heated rooms in parts of the
attic
14 %
Insulated terrace with
wooden floor joists
2 %
Compact roof
19 %
Terrace on concrete floors
26 %
Figure 7. Defect cases for the 10-year period 1993-2002 concerning
roofs, distributed by type of roof (465 cases, 22% of
the total amount of building defects).
In Figures 5–7 building defects concerning external
walls above terrain (i.e. ground level), external
walls under terrain and roofs respectively are broken
down into distributions by type of structure. Only
30% of the building defect cases related to external
walls above terrain is related to timber frame walls.
The bulk of defects related to walls above terrain are
found on walls made out of porous mineral building
materials – with defects on rendered facades by far
being the most common exterior surface problem.
Approximately 20% of the building defects are
reported within the first year, and about 48% of the
defects are reported within 5 years after completion
of the building (Fig. 8).
No. of building defect cases
300
250
200
150
100
50
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
No. of years from completion until defects are being reported
Figure 8. Process induced building defect cases for the 10-year
period 1993-2002, distributed by number of years from completion
until defects are being reported.
A bulk of the defects is related to moisture, and
many types of building defect cases are recurring
items, which indicate a general lack of knowledge
concerning fundamental principles of building physics.
A wide range of classical problems has been recorded,
as for example unfortunate design and use of
materials, inaccurate craftsmanship, structure and
composition of rendering layers and paint on porous,
mineral building materials, inappropriate rendering
layers on facade systems with rendering directly on
thermal insulation, insufficient efforts to protect
against precipitation and insufficient efforts to protect
against moisture in general. These findings are
supporting earlier investigations concluding that the
construction industry is not able to learn from past
experience and that the exchange of knowledge in
construction projects is not satisfactory (e.g. Lisø et
al. 2000).
The building defects archive reveals serious deficiencies
in the construction industry with regard to
knowledge about correct design and construction of
buildings in Norway. These findings are also supported
by earlier case studies of building defect assignments
carried out by the institute. Lisø et al.
(2005c) present a review of typical problem areas associated
with weather-protective flashing. A total of
175 assignment reports associated with defective or
damaged flashing from the period 1963 - 2001 were
analysed. The investigation clearly showed that certain
faults and deficiencies are recurring items. Windowsill/weatherboard
flashings comprised as much
as 41% of the building defect cases associated with
weather-protective flashing. Defects in connection
with parapet flashing comprised 27% of all cases included
in this investigation. With few exceptions, instances
of flashing defects are located in Norway’s
coastal areas.
A review of the archives regarding process induced
masonry defects showed that inappropriate