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

mark wrote:
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?

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

"Lobster" wrote in message
...
mark wrote:
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?

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


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

mark