The function and importance of cavity walling

High rainfall regions can experience condensation on the inside surface of the building shell during cold weather. This is commonly visible on glass doors and windows but can also be found on the walls themselves. In addition to causing damage, the continual dampness results in mould growth and many other health issues.

The winter rainfall regions of the southern and western Cape are particularly susceptible to condensation, due to the differential between heated indoor air and the icy cold outdoor temperatures.

An important revision to National Building Regulations is expected to address the problem through changes to SABS 10400-XA regarding standards for masonry walling, roofing and ceilings, flooring, shading and windows.

Technical experts from the Clay Brick Association of Southern Africa (CBA) have been closely involved in the drafting of the new standard. Mariana Lamont, Executive Director of the CBA explains.

‘No matter how thick the wall or what it is made from, condensation will always be a problem if there is only a single walling layer or “leaf”. Cavity walls have been used since the 1800s to naturally insulate buildings in cold, wet climates like the UK and Europe.

‘The new SANS 10400-XA thermal performance requirement for masonry walling is based on the location, the type of building and the hours of day the building is used. The option is either a cavity wall (with or without insulation) or a composite wall with insulation.