Quick Question - Sealant For Gaps In Rafter Insulation

6 Nov 2014
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United Kingdom
I'm putting 50mm GA4050 between rafters and 80mm GA4080 under the rafters. If my saw is broke (wink) and wanders ever so slightly on the insulation i'm using between rafters, can anyone advise whether i need to plug these gaps with some sealant or not? If so can you suggest a sealant. I'll be taping up the 80mm level and filling gaps at the edges with expanding foam but i don't think the gaps i'm talking about on the rafter layer are wide or deep enough for expanding foam. Just to be clear, I haven't started yet so i haven't got a roof full of badly cut insulation but i'm assuming i will slip up a couple of times and have the odd bit here and there.

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No sealant, just expanding foam.

If you want to do a decent job at fitting between rafters, then cut the panels to size so that you can foam all around them, rather than trying to delude yourself you can cut them to fit tight with no gaps.

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