Blockwork Wall

[mark]

I have planning permission to build on top of my flat roof garage.

The next stage is submission to Building Control. The existing garage has 50mm cavity walls. I am proposing to have this extension done entirely in thermalite blocks. However a rockwall filled cavity of 50mm doesn't seem to meet the insulation requiements. Do you think that Building Control would let me step the inner wall to provide a wider cavity?

The roof will be a conventional pitched and hipped roof with pantiles. With thermalite blocks there is a trade off with strength and insulation. i.e., weakest block has highest insulation. How do I chose which grade I need for strength?

Thanks

mark

[Lobster]

Just ask them informally before you submit the application. Doesn't sound a very stable structure, however. How much "step" were you thinking of? Can't you use 50mm Kingspan instead, which is a much better insulator?

On a separate note - do you know if the garage has adequate foundations for the extra storey? That could be a show-stopper for Building Control otherwise... if you don't have any form of 'proof' they may require you to excavate a test hole so they can see the footings.

David

[mark]

The footings have been seen by BC and approved. Didn't realise that Kingspan can be used in cavities.

mark