Celotex Isover

Insulation for Masonry Partial Fill Cavity Walls

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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 to consider
Product Name Thickness Range Sizes Lambda BBA
Celotex CW4000 40-100mm Width 450mm, Length 1200mm 0.022 W/m.K Tick Icon
ISOVER CWS 32 65-150mm Width 455mm, Length 1200mm 0.032 W/m.K Tick Icon
ISOVER CWS 34 75-150mm Width 455mm, Length 1200mm 0.034 W/m.K Tick Icon
ISOVER CWS 36 50-150mm Width 455mm, Length 1200mm 0.036 W/m.K Tick Icon