Newly constructed buildings will nearly always be vulnerable to cracking for a variety of reasons. However, nowadays we understand much more about why this occurs and what particular controls can be put in place to minimise the effects of movement of building materials and components.
Shrinkage will occur in masonry structures, particularly if blockwork has not cured properly. However, the secondary control to accommodate this shrinkage is the installation of a movement joint.
Movement joints are generally formed to address either contraction (shrinkage) or expansion, whichever will occur first. These terms are used interchangeably in the industry although they are very different. For example, movement joints in concrete footpaths are often referred to as ‘expansion’ joints although they are in effect ‘contraction’ joints as contraction will always occur first as the concrete cures and loses its moisture content.
Unfortunately, buildings can be designed or constructed poorly, with less regard to these controls as identified in the Technical Guidance Documents or Homebond manual.
This crack has formed in the middle of two semi-detached houses in Ballyvolane, constructed in 2005. It is mirrored on the opposite side of the building which is to be expected. The whole building is about 16m in length and 6m in width. It is clear that a movement joint has not been installed and could have been neatly concealed behind the downpipe.
Homebond provide good guidance for movement joints in both brick and masonry buildings. It states that ‘Codes of Practice recommend that spacings of movement joints should be referred to by the building designer. It is not standard practice to incorporate movement joints in semi-detached houses. Based on traditional construction, the minimum recommendation is that in terraces of three or more houses, joints should be built in every two houses unless specified more frequuently by the designer.’ (Homebond, 2008). It also refers to joints at 12m centres or very two houses whichever is less.
Considering the geometry of this building, a movement joint should have been installed. As cracking will normally occur over weak points in a building, it was just unlucky for this homeowner that it occurred on his side.