Cavity closers

16 Apr 2013
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United Kingdom

I'm currently doing a cavity build and I'm not sure if to use cavity closers or not. My cavity insulation is Celotex 75mm and was wondering if I could just cut a 100mm slab, my cavity is 100mm, and use that to close the cavity around the door and window.

Having a search on here, there were some old posts where some people do that and some swear by cavity closers but there was no definitive answer.

Would I be fine closing the cavity with a 100mm cut insulation board? The inside of the build is going to be plasterboarded if that decides anything and I have brick on the outside leaf but only on one side, the other 3 walls are block on the outside leaf and will be painted to seal them.

Thank you :D

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:LOL: Got plenty of Celotex but no cavity closers. Oh well, it was worth a try, I'll get some ordered. Thanks Freddy
You can sandwich a dpc between the outer leaf and the celotex but only if you return the inside cavity to make sure it holds in place
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I have some DPC left over so that would brilliant! May I ask what you mean by "return the inside cavity to make sure it holds in place". I was thinking, with your idea of using the DPC, putting in a 100mm cut of celotex to fill the cavity but have a strip of DPC against the outer leaf. The celotex would be a snug fit and would hold the DPC against the outer leaf. Is that what you meant?
Fair enough freddie but often for a diyer cheaper and slower is ok compared to a tradesman where the extra few quid doesn't matter.

I was only 2 in 1984.... maybe i was born in the wrong era

Traditionally, well in recent tradition, you would turn the inside leaf out towards the outside and form a corner, this would be a cut block which would then be held off the outer leaf by a strip of dpc and a strip of insulation. Usually 25mm.

The danger with just dpc and insulation is that should your dpc slip out at some point over the years as the insulation shrinks a bit then your left with nothing to prevent ingress of damp.

Not sure that would ever happen though.

A cavity closer has no advantage other than speed really.
A proper cavity closer is fool proof. The costs/hassle of rectifying a leak or damp should it ever occur will far out weigh the few extra quid for some proper closers. DIY or not.

The forum is littered with people with damp around the windows because of poorly fitted or ill thought out methods of cavity closing.
That's a cheap price, I can only find them around here for £15 per 2.4m strip :eek:
That's a cheap price, I can only find them around here for £15 per 2.4m strip :eek:

I used cavity closers on a self build project a year or so ago. 100mm cavity, a 2400 length cost around 12 quid.

Simply trim it to size then friction fit the closer. I used a few galvanized clout nails to further secure the closer (medium density blocks). I guess a bead of silicone could also be used, for completeness.

So easy, so quick - the finish looked almost professional. I would advise shelling out, save so you much time and hassle.
Είναι όλα ελληνικά για μένα
Is it?

Dunno why - it seemed quite understandable to me.

Still - you know best what you can and cannot comprehend.

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