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Insulating a ceiling - non standard construction
Daniel 17/12/2025 - 7.58 AM
Hello. This is quite difficult to explain but I will do my best to try and make it clear. My house is classed as non-standard construction. It was originally built as social housing and with a flat roof. At some point in it's life, a pitched roof was added by the council. There are two seperate roof spaces to the house. The main house had a loft hatch added along with the new pitched roof and was insulated as normal. There is a second roof void above a single storey 'extension' type of room. This currently has no access and is extremely difficult to heat and keep warm. I recently employed a tradesperson to install a hatch in this room but upon cutting a small opening in the plasterboard ceiling, it revealed that the newer pitched roof had effectively been built on top of the old flat roof. The only access point between the old flat roof and the new pitched roof space is a hole left behind by the previous owner who removed a chimney breast. I imagine that this hole is letting a lot of cold air through although the room itself is not draughty. It's just very thermally inefficient. Constructed as a pitched tiled roof then below this is the original flat roof boards (some odd material that does not look like modern OSB but looks fibrous almost like compressed straw. Rafters and then plasterboard with a skim finish. When the hole was cut by the tradesperson, it felt very cold and draughty. I was intending to have the hatch installed and an insulation company out to insulate it like a standard loft but upon discovering the old flat roof, think that this is no longer possible (even with the sizeable access hole from the old chimney breast) it would seem futile to insulate over the old flat roof as there would still be the large air gap between the rafters. My main question after all of this rambling and explaining is, Should I board over the old hole where the chimey went through and should this make sufficient difference to the warmth of the room? Or if I were to try and insulate the ceiling, would it be best to take the whole ceiling down and place celotex/kingspan type material between the rafters and re-board and skim the ceiling or simply replace with an insulated plasterboard? I don't really want to add a false ceiling as I can't afford to lose ceiling height. I hope that someone can perhaps offer thoughts or some insight into this. Kind regards
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2 Answers
Handimen (Home & Garden)
PDH Insulations Ltd