Expanding Foam?

[junglejim01]

I've just finished installing rigid insulation boards between the rafters in my attic. 50mm between rafters plus another 50mm with plasterboad underneath rafters. The problem is that the edge of the attic is bare stone so there are varying sizes of gaps along the edges. I was thinking of filling carefully with some expanding foam...any thoughts??
Thanks in advance for any tips.

 

[RedHerring2]

That'll work OK. Foam can be painted after it's cured.
Otherwise, if you're intending dot & dabbing pb (poss with insulation backed) on the walls, the pb might cover the gaps.

BTW, you should have minmum 50mm gap above insulation betwen rafters, assuming you have a non-breathable felt lining the roof.
You can reduce that to 25mm gap min with breathable membrane.
You'll also need to ensure that you've got low level and high level ventilation.

 

[junglejim01]

thanks for that, yeah i've got a breathable membrane + at least 25mm air gap. The walls are going to be plastered so in most places this may be sufficient but i just wanted to help seal it up for greater heat efficiency.

I'm not sure what you meant by low and high vetilation. The attic is about 200 years old with the walls extending to knee height. The seems to be ventilation from the eaves but i can't see anything else.?? Cheers

 

[catlad]

You need ideally to vent at the eves and the ridge to stop condensation.

 

[freddiemercurystwin]

You need ideally to vent at the eves and the ridge to stop condensation.

Not if he has a breathable membrane.

 

[junglejim01]

brilliant, thanks all the help. Gonna need lots of expanding foam now!

 

[catlad]

I would not totally rely on breather membrane for getting rid of moisture that builds up in loft conversions.

 

[emyr46]

I would not totally rely on breather membrane for getting rid of moisture that builds up in loft conversions.

So what would you rely on.

 

[freddiemercurystwin]

I would not totally rely on breather membrane for getting rid of moisture that builds up in loft conversions.

They've been around long enough that there doesn't seem to be any consistent issues or inherent problems within the industry regarding their inability to breathe.

 

[catlad]

Vents eaves and ridge to get rid of the stale air, especially if you are squeezing the gap to 25mm and there is snow on the roof.