Can I build an extension with a single skin timber wall?

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Agent_zed

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Hi,

I'm planning an extension that will be a more modern looking design with a flat green roof and clad with local cedar. For the walls I was thinking of using 6x2 timber which would then have plasterboard on the inside then osb / battens /cladding on the outside. The cavity would then have 6inch of insulation.

Does anyone know if this is an allowable design? Or would building regs need a break in the 6x2's?

I'll obviously run this past the local building inspector but didn't want to go and ask a really dumb question if it's clearly not possible etc.

thanks
 
I'm out of touch now with the current regs, but have in the past when building with timber frame had U value/Standard Assessment Procedure (SAP) calcs done to satisfy Part L and Building Control.

Last big one I built in 2017/18 we used 140mm studs, snap shot picture below of calcs and layers of construction, detail:

U value.png
 
I'm out of touch now with the current regs, but have in the past when building with timber frame had U value/Standard Assessment Procedure (SAP) calcs done to satisfy Part L and Building Control.

Last big one I built in 2017/18 we used 140mm studs, snap shot picture below of calcs and layers of construction, detail:

View attachment 195981
That's really useful thanks.

Do I correctly read that the 15% softwood is the amount of surface area of the edges of the timber that is touching the osb?

Also is the 20mm of celotex across the entire inside wall before the plasterboard?

Thanks
 
To be honest, not a clue about the 15% figure, but yes to the Celotex, goes straight on/over the studwork to make a thermal break with the battening nailed through it to make the service void then ply, and PB
 
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