Celotex Isover

Insulation for Masonry Partial Fill Cavity Walls

Application image
U-value Calculator
Start your U-value calculation >
Use the calculator

Building two skins of masonry (brick and/or blockwork) either side of an air cavity has been the most popular method for constructing external walls in the UK for about a century. From its development to address some of the flaws of traditional solid wall construction, it has gradually evolved in response to improving insulation technology and the development of building regulations relating to energy efficiency.

In a partial-fill masonry cavity wall the residual cavity between the two leaves of masonry is partly filled with either a PIR cavity board or a glass mineral wool (GMW) insulation slab. Typically a 50mm residual cavity is required to be maintained between the outer face of the cavity insulation and the inner face of the outer leaf.

The building detail is for illustrative purposes only. It does not constitute advice and should not be relied upon.

Insulation products
Product Name Thickness Range Sizes Lambda
Celotex CW4000 40-100mm Width 450mm, Length 1200mm 0.022 W/m.K
ISOVER Cavity Wall Slab (CWS 32) 65-150mm Width 455mm, Length 1200mm 0.032 W/m.K
ISOVER Cavity Wall Slab (CWS 34) 75-150mm Width 455mm, Length 1200mm 0.034 W/m.K
ISOVER Cavity Wall Slab (CWS 36) 50-150mm Width 455mm, Length 1200mm 0.036 W/m.K