Lisø PhD Dissertation Manuscript - NTNU

geographically dependent climatic exposure must be established in order to develop
improved standards and design guidelines for different climates.
3.5. Masonry mortar
The masonry mortar must be compatible with the suction rate of the brick in order to
ensure the highest degree of water tightness possible, to avoid the disintegration of mortar
joints and finally to secure the intended load-bearing capacity. The introduction of new
types of clay brick in the Norwegian marked has led to problems due to lack of
compatibility between the suction rate of the brick and the traditionally used masonry
mortar. The Norwegian focus has been on the type of mortar. However, the type of
masonry technique applied may eliminate such problems. E.g. in Belgium and in the
Netherlands it is customary to scrape off and refill mortar joints with a particular
compacted repointing mortar. In Norway brickwork is constructed with fully filled mortar
joints, which afterwards are compacted. The different techniques yield diverse rain
penetration resistance. Edgell and Haseltine [15] demonstrate the possibility of repointing
weak mortar joints to withstand freezing and thawing and gives a draft specification for
repointing.
3.6. Shrinkage and movement defects
The performance of movement joints and sliding layers against the foundation, the most
frequent cause of defect in the presented investigation, is highly critical. Martens and
Vermeltfoort [16] conclude that the rules determining the spacing of movement joints are
primarily empirical and consequently often “a mystery”. Such a basis for movement joint
design has resulted in quite different national rules. The conclusion of Martens and
Vermeltfoort [16], based on an investigation of cracking in façades as well as literature
surveys on the shrinkage and temperature deformation of masonry walls, supports the
experience gained in Norway. More accurately defined guidelines on how to minimize
shrinkage and temperature deformation are urgently required.
3.7. LECA masonry
Light Expanded Clay Aggregate (LECA) masonry needs always to be rendered to ensure
satisfactory air and rain protection. Hence, the correct choice and performance of rendering
systems is crucial. Such walls have to be built as shell bedded walls (i.e. a wall in which
the masonry units are bedded on two masonry mortar strips at the outside edges of the bed
face of the units) to avoid capillary suction through the wall via the mortar joints. Details
identified with carrying out of flashings, doors and windows are even more important for
LECA masonry than for bricks, as LECA masonry walls are often constructed as compact
walls without separate wind and rain barriers. It is also essential that the sliding layer
(damp proof course) adjacent to the foundation be properly constructed. The distance
between movement joints must be smaller for LECA masonry than for bricks, as the
moisture movements are much larger for LECA masonry.
3.8. Weather-protective flashings
Flashings must always be designed and constructed so that water is directed away from the
structure, and rain or snow is not led underneath the flashing with the consequent risk of
leaks [4]. Generally, a flashing should not be the sole protective layer against water
ingress. Flashing should function primarily as a drainage covering or an external rain
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