How much to allow for an external wall?

Question

I am building a new extension which can extend no more than 4m from the house.What will the internal size be?My external walls + finish in my house are around 30 cm , but it is around 20 years old.I understand there are new building regulations which focus on the energy efficiency of any additional building attached to the original house.Will the external wall plus inslation and finish be more tha 30 cm?

Answer 1

If your walls are 30cm thick built with traditional building materials IE brick block there should not be a problem.  you can either use a full fill cavity insulation like rockwool or a partial fill material like celotex.

Answer 2

3 1/2 inch studs covered with 1/2 inch plywood on the outside and 1/2 inch sheetrock on the inside.   House wrap does not take up any space.   Which leaves possible use of exterior board insulation (used when you side your house with vinyl).   Plus the thickness of whatever you have on the outside (brick, stone, clapboard, siding.....etc).

So far, that 1s 13 cm.    What do you have on the outside of your house