External walls

Constructing Party Walls

This article is provided by H+H

When deciding what materials to use for party walls, consideration needs to be given not only to the performance of the wall itself, but also to potential heat loss through junctions with external elements. Using an energy-efficient material such as aircrete in party walls, in conjunction with aircrete inner leaves on external walls, can reduce heat losses at thermal bridges by as much as fifty per cent - the equivalent to the effect of adding 10-15 millimetres (mm) of insulation to the external walls.

Thermal performance

Since the changes to the building regulations Part L in 2010, party walls have had to meet strict thermal performance criteria. This is best achieved by using a cavity wall construction, where the cavity is filled with insulation material - a very similar design to the external walls.

Thermal Bridging

Thermal bridges occur where the party wall breaks the continuity of external fabric insulation – for example at junctions with external walls, floors and roof.  Heat losses associated with these thermal bridges can significantly affect the thermal performance of the house.

Using aircrete significantly reduces the thermal bridge effect at junctions as it has a far better thermal resistance than denser concrete blocks. 

View a series of calculations to demonstrate this effect (external link).

These calculations can be used in the design of party wall details.

Acoustic performance

Another key performance characteristic for party walls is sound insulation – with requirements set out in Part E of the Building Regulations. Although light weight would not normally be associated with acoustic performance, the close cellular structure of  aircrete gives it excellent sound insulation properties relative to its weight.

To determine whether a wall construction detail will meet the requirements of Part E, reference can be made to Robust Details (external link). These are independently assessed design details that can be used in the design of wall constructions. 

Robust Details demonstrate that aircrete party walls will provide the same level of acoustic performance as dense aggregate blocks, but with all the benefits of using a lightweight block.

To find out more about building masonry walls – including party walls – with aircrete, download this information from the manufacturer.