External Walls: Cavity wall Construction

The external leaf protects the structure from the penetration of moisture while the inner leaf provides the main structural support for the building.In an external cavity wall construction, each leaf has a distinct purpose.  The external leaf protects the structure from the penetration of moisture while the inner leaf provides the main structural support for the building.  Celcon Blocks fulfil both of these requirements.

For the loadbearing inner leaf, a range of Celcon Blocks of different strengths are available, with the choice dependent upon the height and design of the building under construction.  Wall ties conforming to BS EN 845-1 should be used in cavity wall construction, with a minimum embedment of 50mm into each leaf.

With its inherent thermal efficiency, aircrete is an ideal material for constructing external walls: typically a cavity wall constructed of two leaves of 100mm Celcon Blocks and 100mm of insulation material will meet the requirement of Building Regulations Approved Document L 2013 with its focus on a Fabric First approach to energy efficiency in new housing.

As required U-values have been driven down, the significance of heat loss through thermal bridging increases. Non-repeating thermal bridging at the junction of building elements (floors, walls and roofs) can account for as much as 50% of the fabric only heat loss.  The use of H+H aircrete can significantly reduce the thermal bridge effect at junctions as it will have a far better thermal resistance than denser materials.  Where aircrete is used both for separating walls and the inner leaves of external walls, heat losses at thermal bridges can be reduced by around 50%.  More information on thermal bridging is found on this page.