If you are installing SureCav, or just deciding to use SureCav25 instead of SureCav50, the gains in space when installing SureCav, compared to using a traditional concrete backing block are not to be ignored. A reduction in wall thickness of just 25mm, when using SureCav25, will increase the internal dimensions of the property by 50mm in each direction and result in a 1.6% increase in floor space over 2 floors.
All the following information is based on a design including at least 75mm insulation, to achieve the Part L Building Regulations with a U-Value of a minimum 0.18W/m2K.
The question is often asked; What difference will it make if I install SureCav25 instead of SureCav50? It is important to note that he properies of the 2 sheets are identical, apart from the obvious difference in depth i.e. 25mm or 50mm. Then, both size sheets have BBA approval, in all weather zones. Most importantly, by installing SureCav25, you can gain an extra 1.3m2 floor area, over two floors.
Surecav25 saves 25mm of cavity and results in 1.6% of extra internal space on an average two storey three-bedroom house. If the house sells for £280,000, it is the equivalent of £4,800 of extra value for a cost of only the SureCav25!
Worst case scenario: A 75mm residual cavity is often specified for areas in high exposure zones around the UK.