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- 15 Jan 2024
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Hi,
I am looking into installing 25mm thick PIR Insulation Foam Boards (Celotex) in my loft. Its a normal standard pitched loft (triangle shaped). Currently my loft side vertical walls going in traiangular shape has battens which hold the roof. Behind the battens is felt. The battens appear to be 4 x 2 inch C24s. The PIR boards will fit inside the frame (battens) as friction fit. The battens are 57cm width between each other (inside measurement between the battens). My question is what size width would I ideally need to cut the PIR boards. I have read somewhere online to add extra half inch (13mm / 1.3cm) to your measurements and this will friction fit perfectly between battens but that isn't correct because it won't fit. I know another option is to cut it short and use expansion foam but this is a messy job and we have carpets in loft. I was wondering whether anyone knows how much extra width should be added to existing width in order to friction fit the boards perfectly. I tried cutting 57cm exactly but the boards are not stable, too loose.
Thanks.
Isaac
I am looking into installing 25mm thick PIR Insulation Foam Boards (Celotex) in my loft. Its a normal standard pitched loft (triangle shaped). Currently my loft side vertical walls going in traiangular shape has battens which hold the roof. Behind the battens is felt. The battens appear to be 4 x 2 inch C24s. The PIR boards will fit inside the frame (battens) as friction fit. The battens are 57cm width between each other (inside measurement between the battens). My question is what size width would I ideally need to cut the PIR boards. I have read somewhere online to add extra half inch (13mm / 1.3cm) to your measurements and this will friction fit perfectly between battens but that isn't correct because it won't fit. I know another option is to cut it short and use expansion foam but this is a messy job and we have carpets in loft. I was wondering whether anyone knows how much extra width should be added to existing width in order to friction fit the boards perfectly. I tried cutting 57cm exactly but the boards are not stable, too loose.
Thanks.
Isaac