Celotex help !!!

[FRAN1870]

Celotex is driving me mad .... Old building, irregular gaps in rafters, twisted rafters, bent rafters !!

The larger gaps I can fill with expanding foam .... But what about the smaller 5mm or less gaps where I can't get the nozzle in.

Any tips?

 

[noseall]

If using the DIY type broad plastic nozzle, just hammer it flat for tight gaps or use the silicone gun. The foil tape will get the smallest of gaps ion any case.

 

[Gerrydelasel]

I've been wondering, does it matter? I mean, you've insulated 99.9% of the available area, what does it matter if there are thin gaps and cracks in it when it used to be 'one giant gap'?

 

[londoner1]

Insulation tape??

 

[geraldthehamster]

I suggest using an applicator gun - the nozzle is very small and you can control the flow. So much easier, and less messy.

 

[garyo]

I've been wondering, does it matter? I mean, you've insulated 99.9% of the available area, what does it matter if there are thin gaps and cracks in it when it used to be 'one giant gap'?

My thinking is 'yes': The insulation becomes pointless if the air can leak around the side. It's like leaving all your windows open and wondering why your central heating isn't very good. Probably massively dependant on whether your 99.9% is actually 99.9% or whether it's really 98.2%

 

[Gerrydelasel]

It's like leaving all your windows open and wondering why your central heating isn't very good.

Surely it's like leaving all your windows open a crack? Not 100% perfect, but way better than when you had no windows at all!

 

[garyo]

Surely it's like leaving all your windows open a crack? Not 100% perfect, but way better than when you had no windows at all!

Yeah - you're probably right. And if you cover the rafters with foil tape that will help a lot too.. like covering your window cracks with clingfilm.

OP - are you also putting another layer of PIR under the rafter too anyway, or are you only going between the rafters?

 

[noseall]

Sealing the gaps is there to prevent air movement (below the venting layer) and moisture migration. Think 'robust'.

 

[FRAN1870]

Surely it's like leaving all your windows open a crack? Not 100% perfect, but way better than when you had no windows at all!

Yeah - you're probably right. And if you cover the rafters with foil tape that will help a lot too.. like covering your window cracks with clingfilm.

OP - are you also putting another layer of PIR under the rafter too anyway, or are you only going between the rafters?

Just between ... hence the need for a good seal