Extension wall material

[AndyDavis]

I'm building a double storey extension, would it be better (stronger, resistant to frost, better heated) to build the external walls using Celcon solar blocks (235mm thick) only or a cavity wall of brick and Celcon solar blocks (100mm thick), with Rockwool foam insulation in the cavity.

Looking in the forums I've notice some concern about Celcon blocks being prone to frost, how serious is this?

 

[murraysnudge]

You don't care what it looks like then Andy?

 

[AndyDavis]

It'll all be rendered with white cement. I wasn't planning anything too extravagant!

 

[murraysnudge]

Just my opinion, but I always think an extension should match the rest of the house and ideally look as if it was built at the same time. That means using a matching facing brick(and no flat roof ). If the rest of the house had suffered frost damage with spalled bricks then I could understand your concern to use something else. Perhaps it has, and you are planning to render the whole house?

 

[AndyDavis]

Couldn't agree more. The house is currently pebble dashed, that's all coming off and the whole house will be rendered.

 

[masona]

I've notice some concern about Celcon blocks being prone to frost,

Celcon block’s are moisture resistance and high thermal efficiency so I can't see how they can be prone to frost.

 

[murraysnudge]

OK, thanks Andy but I thought from your post here that it was a facing brick extension.
....or are you building two extensions?

 

[AndyDavis]

masona - The frost issue is mentioned in some literature that I got from Celcon, however, I gave their technical department a call to find out more and they said that its no longer an issue.

murraysnudge - my building regs says use a solid 250mm celcon solar block, expect that celcon don't make 250mm blocks anymore. I've tried a number of others including Thermalite but no one seems to make a 250mm block any more, although I'm told Durox might. All the blocks go from 215mm to 265mm. I'm thinking that if I can't get any 250mm blocks then I'll build a cavity wall of either brick-block or block-block, with Rockwool in between.