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We have a massive attic which has ben floored. I'm wanting to plaster board it to make it look better and be more useful for locking children in! I thought about insulating between the joists on roof first but partner says this will lead to damp issues, any suggestions?
do you mean joists or rafters? the sloping bit is rafters
can't see how it would lead to damp issues myself but I am not a pro roofer / builder
Rafters, Sorry! didnt want to say sticky up bits and show my level of expertise!
Think if you leave a gap between the insulation and at the top and bottom to allow airflow then you'll be OK. If a very steep pitch you might want a couple of vents halfway up or something too in order to enable a flow. But yes, you do need to be mindful of damp and need to make sure air can circulate around the roof felt and get from the eves/soffits area and up the roof between the insulation. This will also be beneficial in summer.
Building regs require minimum 50mm gap for airflow between top of rafters and top of insulation between rafters.
Easiest way would be insulated plaster board on top of rafters. Much better job as well no fiddling around trying to get a good fit inbetween rafters etc insulation would also be even across rafters as well. Nice big air gap behind . Jobs a good un
As above 50 mm minimum gap between I insulation and roof (felt or sarking board). Also make sure to leave space for air to flow in the bottom and top of the gap to take condensation away.
Insulated plasterboard is heavy so it can be easier to put insulation up first then plasterboard on top. If you're wanting it to be considered a room in the future there are minimum insulation standards needed. If just to make the attic less unpleasant to escape to then just use whatever.
When I was thinking of doing ours a few years ago a mate who works in building control said to use 50mm celotex or the like inbetween the rafters to leave a 50mm gap then overboard with 100mm or 50mm celotex, can't remember which now.
I still have fibreglass in between the joists. 🙂
When I was thinking of doing ours a few years ago a mate who works in building control said to use 50mm celotex or the like inbetween the rafters to leave a 50mm gap then overboard with 100mm or 50mm celotex, can’t remember which now.
Celotex have a guide for the ventilation gap:
[url= https://live.staticflickr.com/7447/9914758565_3a9ac3ac80.jp g" target="_blank">https://live.staticflickr.com/7447/9914758565_3a9ac3ac80.jp g"/> [/img][/url][url= https://flic.kr/p/g78Jic ]Celotex between rafters[/url] by [url= https://www.flickr.com/photos/brf/ ]Ben Freeman[/url], on Flickr
As for overboarding, up to you as to how much insulation you want / head height reduction you can take....