Aircrete for residential extensions

UK homeowners move, on average, every 20 years. Two decades is a long time to expect a home to meet the needs of a developing family, so it is hardly surprising that extensions are a popular way of creating the space needed while avoiding the trouble and expense of moving.

And when it comes to adding a rear, side or even double-height extension to an existing home, aircrete blocks are ideal for external walls.

Under the current rules around permitted developments most homeowners can build a rear extension of up to 3m or a side return extension, or even add a storey in height to their home without needing detailed planning permission.

There are constraints within this permission, however, one of which is the stipulation that extensions should match the aesthetic of the building onto which they are added. This will typically mean a brick or rendered façade, making the choice of a cavity wall construction using brick and block or twin block walls an obvious one.

Thermal performance

Extensions will need also to meet the thermal performance standards of Approved Document L1B. The easiest way to do this is to ensure that the external walls have a U-Value of 0.28W/m2K or lower. This is simple to achieve with a cavity wall construction using Standard Grade Celcon Blocks with around 75mm of insulation in the cavity. Full details of the U-Values of individual wall constructions can be found here. 

Higher levels of thermal performance can be achieved with different types or widths of insulation and with Solar Grade Blocks or Thin-Joint construction.

Particular care needs to be taken at the junction between the new build extension and the existing house structure in order to allow for differential movement. The older structure may well have less robust foundations and be subject to greater movement in extreme weather. Advice on constructing this joint detail can be found here. (p16). 

Aircrete walls are ideal for kitchen extensions where load-bearing cabinets or appliances need to be fixed to the wall. Aircrete provides an appropriate substrate and advice on the right fixings for these applications can be found here (p35). 

On site, aircrete blocks will be welcome. Their lightweight structure makes for easier lifting and handling while they can also be cut with a handsaw for detailing.

Aircrete products from H+H are available from builders’ merchants across the country. To find your local stockist, go to the bottom of this page.