Cavity walls are a common feature in modern properties and have several advantages over solid brick walls. They provide good insulation for heat and are cheaper to build as they do not need to be as thick. They also give protection against efflorescence, which is the white marks that can appear on the external surface of a wall when water penetrates through the brickwork leaving crystalline salt deposits.
In order to be effective a cavity wall requires considerable care in its construction. Failure to take this precaution may result in the outer skin of a building being exposed to appreciable movements in temperature and moisture content, resulting in stresses which produce cracking. In order to prevent this it is usual to incorporate vertical control joints in the outer wall.
The cavities in cavity walls are often filled with mineral wool or another insulating material. The choice of materials depends on many factors such as environmental considerations, the thickness of the wall and its position, the cost and durability etc. It is generally best to use a low water vapour permeable type of insulation as this will help to reduce the risk of condensation within the wall.
The two skins of the wall are bonded together by metal ties known as ‘wall ties’. These are usually of the stainless steel variety, which is less prone to corrosion than the traditional mild or iron steel ties and as such they will remain in service for much longer.