Lisø PhD Dissertation Manuscript - NTNU

Table 1. Process induced building defects inflicted on masonry structures (302 building defect assignments
related to masonry in the 20-year period 1983-2002). Categories of causes of defects are distributed by
frequency according to the percentage of building defect cases associated with the main cause of defect (see
Fig. 2 for illustrations)
Main cause of defect Explanation
A Shrinkage and thermal movement defects
(34%)
Movement joints missing, absence of sliding layer between
masonry and foundation, concentrated tension loadings, locking
of masonry to other structures
B Deficient flashing (26%) Deficient door/window/parapet flashing, faulty drainpipes and
roof gutters, faulty door/window installation
C Deficient rain barrier (25%) Non-watertight/ porous mortar joints or disintegration of the
surface, faults in composure of the rendering
D Faulty painting system (18%) Unfortunate choice of paint, paint that is too vapour tight
E Insufficient durability of masonry units (16%) Low frost resistance of bricks and mortar, sulphate attack on
block
F Deficient drainage of the wall (12%) Too narrow air-gap, mortar bridges between outer leaves and rear
wall, missing drainage opening at bottom of wall
G Lack of compatibility (adhesion) (11%) Inadequate adhesion rendering/substructure, lack of compatibility
mortar joints/masonry units
H Reinforcement corrosion (9%) Corrosion on reinforcement
I Under dimensioning (8%) Anchorage to rear wall missing, insufficient bearing capacity,
earth pressure, overload
J Settling/ Settlements (7%) Settling defects, soil mechanics
K Moisture absorption from the ground (7%) Raising damp, capillary action, deficient drainage
L Aesthetic problems (4%) Organic growth, unsatisfactory colour and structural variations,
efflorescence of salts (not causing defects)
M Salt eruption (3%) Crypto-efflorescence of salts causing scaling of rendering or
bricks/blocks
N Thermal bridges (3%) Heat loss, condensation, staining, discolouration
Process induced building defects inflicted on masonry structures are presented in
Table 1, and illustrated in Fig. 2. The masonry defects are grouped according to a system
developed as part of the examination. Main categories of causes of defects are in Fig. 2
distributed by frequency according to the percentage of building defect cases associated
with the main cause of defect (thus, the percentage of defects do not add to 100%).
Shrinkage and thermal expansion/contraction without the necessary countermeasures are
the most common cause of defect, registered in one third of all cases of masonry defects
analysed. Furthermore, the investigation reveals that two thirds of all cases comprise faults
in the execution of the actual rain barrier (non water-tight mortar joints and rendering),
drainage from the air gap (insufficient air gaps, mortar bridges between outer leaf and rear
wall as well as missing drainage openings at bottom of wall) and the execution of window
and parapet flashing.
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