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Roofing

Improving insulation of flat roof internally

Anonymous user 28/02/2024 - 3.57 PM

I have a room at the back of my garage, about 4.5 x 3.5m built in 1980. It has a large double rad that's plumbed into the main CH. The temperature can be 5c different.There are 3 external walls, two windows. There is about 80mm of fibreglass between the felt roof and ceiling. There is plenty of headroom. I'd like to install extra insulation internally. I should be able to add horizontal lengths of wood, screwing into the existing ceiling joists add kingspan on the void and then celotex as the new ceiling. Am I right in assuming I don't need to worry about vapour barriers etc as it already has insulation ? Is it worth doing something similar with the walls am I better off getting someone to blow insulation into the cavity or is that likely to give me problems later on? thanks

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1 Answer

Anonymous user

If you have a warm roof setup it should be fine to just overboard with kingspan or a equivalent foil backing insulation, Depending on how thick you want the insulation you can just overboard with 40mm kingspan and plaster board and use 60mm drywall screws to hold it all up and then plaster over the new plaster board. If you want 100mm kingspan it properly be easier to rip the old celling down and taking the 80mm rock wall out and providing you have enough room put the 100mm king span back in between the rafters and then 40mm overboard that with king span and plasterboard with 60mm drywall screws and plaster the Celling for a finish, If you have a cold roof setup just make sure you have enough air flow in the ceiling you need at least 55mm gap between the ceiling and the insulation for air flow. I hope this helps

Answered14 January 2021