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Cold deck insulation thickness

We are installing a cold deck on our extension (cold deck due to height). However when trying to work out what Insulation we need it has become rather confusing! We have used 150mm timbers (suitable for the span) but now can’t seem to find anywhere that says which Insulation is suitable. Theoretically it should be 100mm as if you need to leave a 50mm gap then you couldn’t have any more than 100mm but I feel that isn’t enough!

What would we need to get passed the latest building regs?!

Any help is much appreciated!! And Merry Christmas!

1 Answer from a MyBuilder Roofer

Best Answer

100mm solid board insulation between the beams then you can use thermal plaster board internally to prevent cold spots.
Good luck Alex


Answered 24th Dec 2017

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