What wall cavity size on new build/extension these days?

[RomanAbramovich]

..the builder tells me 100mm cavity is now standard. However, I've seen some plans lodged with my local authority that specifiy 85mm cavity. Meanwhile last time I extended 75mm cavity was used!

The inner skin will be aircrete type lightweight blockwork, does the combination of inner skin material and cavity insulation product used govern the cavity size? Intend to use dritherm batts.

I want the cavity to be less, to increase internal room size (albeit fractionally).

Cheers.

 

[garyo]

Depends on the materials used for the inner leaf, insulation, outer leaf, and internal finish. Take a look at page 5 and 6 of this PDF and you'll get a feel for the options.

http://www.harborough.gov.uk/downloads/HDC_12_U-Values_of_Elements_1_.pdf

I've no idea what the 'most common' construction is nowadays. I'd be interested to know myself.

Gary

 

[noseall]

A typical and frequently used cavity is 100mm fully filled.