Things I have learnt this week: Low expansion foam

[Tim S]

Hi,

Part of a new mini series :)

The other day I needed to fix some celotex in place in a rather fiddly location (bay window ceiling retrofit) so it wasn't possible to make it all a snug fit.

Tried some of the Siroflex PU drywall adhesive

it seemed to be pretty suited to the job:

very sticky, expands relatively little (perhaps x2).

The conduit are drops for any future lighting in that area.

Now I'm off to B&Q to see if I can rig a bit of metal tube and plastic pipe to make a nozzel extension for my foam gun - that upside down work was fiddly and I did get as much foam on me as on the board!

Cheers

Tim

[lardconcepts]

Glad you posted that - I'm starting to think about insulating the walls too - any Celotex or similar information is always welcome!

[geraldthehamster]

You actually get a much better fit, and seal, between Celotex and rafters/joists if you cut it slightly undersize, hold in place with pins or similar, then foam it in. I did this recently for a stud wall built out from a single-skin brick exterior wall, using window/door sealing foam (the low expansion, waterproof stuff that window fitters use when replacing windows with plastic excrescences). Not only was the result vapour-tight, but also very strong - you could lean on the Celotex panels, and they weren't going anywhere. Possibly a bit uneconomical if you have a lot to do, though a little foam goes a long way, in this application. If you *do* have a lot to do, consider buying one of those cleanable foam guns that screw into the top of the foam cartridge. Soon pays for itself in the number of blocked, part- used aerosol cans that you are no longer throwing away ;-)

Regards Richard

[Tim S]

lardconcepts wibbled:

Glad my senile wibblings are occasionally useful :)

I used BallyTherm - got it from a mate of the bloke John Rumm recommended in Essex at a very reasonable price. Pays to shop around for that stuff - do not buy from a builder's merchant unless you have thumbscrews!

"2nd grade" is worth seeking - it's a bit dinted, perhaps reclaimed excess from a bigger building job or just slightly out of spec. In practice I have found little of consequence wrong with my batch, especially as for many domestic jobs you are cutting it down so dinted edges are easily lost.

Cheers

Tim

[Tim S]

geraldthehamster wibbled:

I have come to that same conclusion - especially for fiddly fits where there's wood everywhere, rather than nice parallel rafter runs. Makes less mess too as you are not perpetually rubbing the sides off stuffing it in.

Yes I have a gun and I agree totally. I do wish though that they'd make one with a proper screw on flexy extension nozzle though. Pratting around with bits of plastic tube that fall off and spray foam everywhere is a bit painful. I also picked up the trick here of not cleaning it out but leaving the can attached if doing a run of work. Doesn;t seem to do any harm and saves gallons of cleaner.

Cheers

Tim

[Tim S]

Tim S wibbled:

BTW - I found (also a tip from here) that a bread knife makes less mess when cutting it - use the wibbly blade, not the sawtooth version.

I haven't found the dust to be too bad on me in small doses, but it's allegedly a mechanical irritant so a mask or avoidence to breathing it is advisable.

I find it more of a problem on my eyes - like getting sand in them.

Cheers

Tim

[David]

Sounds good, I want to get the solid walls in our house insulated soon.

[John Rumm]

How about, 1/4" rubber hose as used for a manometer, clamped on the end with a small jubilee clip? A plumbers merchant will have the hose.

Yup, tis what I do. Just scrape the nozzle clean and you are ready to go.

[John Rumm]

On the inside or the outside? I am looking at doing the latter here.

[geraldthehamster]

That's what it said to do, on the destructions that came with mine. Just screw the regulator valve shut. If no air can get to it, bringing moisture, then it's not going to go off.

I would recommend the low expansion closed cell foam, though, for this application, rather than the less controllable stuff used, apocryphally, for destroying canoes ;-)

Regards Richard

[David]

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