Relating to another question about loft conversion I also want to fill up the gaps in between the trusses on which the roof tiles lie on.

So during allot of build I heard here and there that some lofts should not completely seal off the space outside the tile and inside the tile because massive pressure differences in windy situation can cause the roof to implode or explode because there is nothing relieving the pressure. But that is not the case for all types of pitched roofs Problem is I do not know when this applies or not.

enter image description here

enter image description here

I have an idea to block piece by piece with a piece of plank- fill it with expansion foam and let it grow and easily overflow.. piece by piece(painfully slow) but end of day its extremely light weight and are porous to an extent. I do not want place plaster board as they weight too much. Then I can just smooth the foam and paint it even with the joists also saving head space (its already a bit tight in some place. I do not want to do this all the way to the bottom. Just the top to about 3/4 way down. The last 1/4 length I want to convert into cupboards / drawers - so they are not air tight but also add extra protection from cold. The space in-between the load bearing wall and where the trusses lie onto are not insulated.. I think It has to stay like that.

Any suggestions? I am a bit stuck on this...

2 Answers 2


In the US, you can find rigid insulation panels of polyisocyanurate foam


and polstyrene foam


These can be cut to fit tightly between studs or rafters, can be flush with the face of the wood and are thick enough to be self supporting. They are usually sealed to the wood using broad tape, such as aluminum.

They are not cheap and not very strong if hit, but have a very high R value.

They also could be covered with either very thin drywall or the new ultralight drywall.


I'd go with fibreglass insulation and 1/4 inch drywall or thin plywood. Just don't throw anything at it, or you'll poke a hole in it. Also, leave a gap at the top and bottom, and the air pressure issue is irrelevant.

Another, cheap options is to simply staple up cloth. It's not like this space is ever going to be a finished entertaining area, so you don't have to be too finicky.

  • 2
    You also might consider stapling up house wrap and shoot a coat of paint on it.
    – Bob
    Commented Aug 2, 2012 at 17:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.