Internal insulation and BC

[Tim Streater]

There was some reference in a previous thread to the notion that although one ought to be able to add internal insulation in an older building (such as a

20s or earlier house with no cavity above the ground floor), that Building Control would prevent this, as it would be a "modification" that would be disallowed, with BC insisting instead that the mod be to bring the upper floor to "current standards"? Is this the case or am I mis-remembering the point that was being made. If I'm not, then what would "current standards" be in such a house?

[Robin]

The "current standards" are just that, and apply to a new build as to a change to an existing wall, floor etc. For those see e.g. Approved Document L1B.

But you aren't required to do more than is cost-effective. So e.g. when we had a new roof here I fitted PIR insulation in the low-pitched roof on the back extension to the then current standard *except* where doing so would have reduced the gap for air circulation too much. BCO signed it off without comment.

[Andrew]

If you replace more than 25% of a flat roof or replaster more than

25% of the total area of your outside walls then you are supposed to upgrade the whole lot.

However, after watching Homes under the Hammer a few times you will soon come to the conclusion that people don't bother unless they are doing other work that the BCO has to sign off.