Vapour control layer and celotex loft quickie.

[arthurdap]

Hi all.

I've battened 50mm Celotex from Wickes onto my rafters (Product Code: 190544) . But should I have a vapour control layer?
Also do I need to keep an air gap between the external wall and celotex?

Any help would be great thanks.

P.S. Any body know whats best to fill some gaps between chipboard flooring and celotex covered plasterboard? Pollyfilla maybe?

 

[skaboy607]

I'm no expert and prepared to be shot down but I think your vapour protection should be installed as final layer negative side I. E into house.

An air gap will always help with u value.

 

[arthurdap]

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• arthurdap
• 19 Sep 2013
• 1

Thanks for your help, it's much appreciated. This should be a pic of where I'm upto so far. I wasn't sure if the celotex foil would stop moisture or even really the purpose.
Is it to basically stop damp/condensation lingering around the wood structure and rotting it.
Thanks

 

[geraldthehamster]

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• arthurdap
• 19 Sep 2013
• 1

Thanks for your help, it's much appreciated. This should be a pic of where I'm upto so far. I wasn't sure if the celotex foil would stop moisture or even really the purpose.
Is it to basically stop damp/condensation lingering around the wood structure and rotting it.
Thanks

The foil provides a vapour barrier; if you tape the joins between the boards you don't need an additional barrier.

The purpose of the vapour barrier is to prevent warm air inside the space penetrating into the cold space behind the insulation, and moisture condensing out of it onto the timber, etc.

Cheers
Richard

 

[arthurdap]

Thanks Richard. That's a perfect description. I added a couple of other pictures now.
So i can fill all gaps between the wall and the celotex with thin slithers of celotex and foil tap to fill all the gaps.
I was thinking of putting some thin bits of wood onto the wall and fixxing celotex to it to insulate the outer wall. Is that a good idea do you know?

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• arthurdap
• 19 Sep 2013
• 1

At the ridge i left a 3" gap for air flow over the top but once the last bits go up i'll need some soffit vent won't I too?


Thanks again for you time and help?

Regards Arthur

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• arthurdap
• 19 Sep 2013
• 1

 

[geraldthehamster]

Thanks Richard. That's a perfect description. I added a couple of other pictures now.
So i can fill all gaps between the wall and the celotex with thin slithers of celotex and foil tap to fill all the gaps.

You can; alternatively expanding foam is your friend

I was thinking of putting some thin bits of wood onto the wall and fixxing celotex to it to insulate the outer wall. Is that a good idea do you know?

Depends what's on the other side of the wall. Unnecessary if it's an insulated cavity; otherwise I would batten it with 2x2 timber and fit 50mm Celotex between the battens. If it's a solid wall between you and the outside it might be an idea to put a membrane between the wall and the timber.

At the ridge i left a 3" gap for air flow over the top but once the last bits go up i'll need some soffit vent won't I too?

Soffit vents and in an ideal world also ridge vents - unless your roofing felt if of the more modern breathable membrane type, in which case in theory I don't think you need a ventilated gap at all (someone please correct me on this if I'm wrong).

Disclaimer: I'm not a builder but have done several jobs like this on my own house and a friend's.

Cheers
Richard

 

[arthurdap]

I'm so glad there's a thanks button for your help.

It's an out side wall but i'm not sure if it's a cavity or not. I know we couldn't get cavity wall insulation as not all our wall were. I can pull the extractor hose about and check though.

Do you think it be possible fix the celotex directly to the wall, then I wouldn't need the vapour control?

 

[geraldthehamster]

I'm so glad there's a thanks button for your help.

It's an out side wall but i'm not sure if it's a cavity or not. I know we couldn't get cavity wall insulation as not all our wall were. I can pull the extractor hose about and check though.

Do you think it be possible fix the celotex directly to the wall, then I wouldn't need the vapour control?

It won't really hurt to do it, even if it is a cavity wall.

Yes, you could stick the celotex directly to the wall. I guess you would use a PU adhesive, though I've not done this. Depends what you want to do with the wall afterwards - if you ever wanted to fix to it, or put up some storage shelves, the battens would be useful to fix to.

Cheers
Richard

 

[TheVictorian]

Looking at the brick work I would suggest that this is not a cavity wall.

 

[arthurdap]

It's really just gonna be used for light storage up there. But i'm considering my old childhood hobby of model trains and may have some thing up there at a later date.

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• arthurdap
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These are my pictures so far, incase it helps any one. I used wicks 22mm boards on the centre and old home base ones about 18mm on the outside. Any sagging felt/lining stuff I supported with chicken wire stappled between rafters. about 1' from the edge I batterned vertically joist to rafter some 3/4 x 1.5" and fixed celotex then platerboard. I just thought this area is more likly to get bashed by boxes.
I just need more than my 1 bulb. As it's head hight and I can see my self walking into it. Then you can guess. Break glass and cut head, electrocuting and fall through open loft hatch.
I might look at led strip lights I saw somewhere, low profile, low voltage and won't generate heat.

Thanks for all the help folks. I'll post a finnish picture so you can see how your help helped me.

 

[AdamCH]

Soffit vents and in an ideal world also ridge vents - unless your roofing felt if of the more modern breathable membrane type, in which case in theory I don't think you need a ventilated gap at all (someone please correct me on this if I'm wrong).

Cheers
Richard

25mm gap with the correct breathable membrane I believe looking at the Celotex website.

 

[arthurdap]

Nearly all done. This weekend I hope to finnish it all. Gap filling and tapping all the gaps.

 

[arthurdap]

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• 29 Sep 2013
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Nearly done but never enough hours in the weekend. Need more tape too.
A big thank you for everyones help.

 

[monty77uk]

Sorry to dredge this up but doing something similar and wondered if you had more pics? Did you plasterboard? Any issues?

Cheers!