Sealing a cavity

[dickm]

Not entirely woodworking, but there are ingenious folks on here who may have some ideas to solve a silly problem. Had an extension built on the side of a 1970s timber frame/block clad bungalow. This means that part of the original cavity wall is now an internal wall and there is a howling gale through the cavity. Trying to think of a way of sealing the cavity so that the heat loss from the timber framed side isn't monstrous. The piece of wall is about 3m long by 2m high, and there is access to the cavity at one end via a new door opening. My first thought was to get the cavity professionally filled with blown insulation, but firms aren't interested in small jobs like this. Next thought was to try and insert timber fillers from the open end top and bottom, but difficult because of randomly (well, irregularly) spaced wall ties. And that would still leave one end open. So been thinking along the lines of drilling holes through the blockwork and using gun-foam, but I suspect it will slump in the cavity and leave gaps.

So open to ingenious but not exorbitant suggestions.

 

[Steve Maskery]

Tricky-dicky.
If you are not averse to a few holes, I would think that a trade-box of PU foam would do a pretty decent job. It's not a huge wall and so is definitely in the DIY spectrum.

 

[Rorschach]

Lots of cans of spray foam, if you buy in bulk it is probably still a lot cheaper than getting someone in.

 

[Dan j]

You're likely right in thinking the foam will slump. A light spray of water will help the foam to stick slightly better. You can probably buy a lot of foam for the price of getting insulation blown in.

Is there any chance of accessing from above in the loft space?

 

[Rorschach]

You're likely right in thinking the foam will slump. A light spray of water will help the foam to stick slightly better. You can probably buy a lot of foam for the price of getting insulation blown in.

Is there any chance of accessing from above in the loft space?

Access from above would really help with the foam, as would making up a longer nozzle to help direct the foam where you need it.

 

[RobinBHM]

Close off with gun foam or brush strip and fill up space with polystyrene beads?

 

[Phil Pascoe]

You're likely right in thinking the foam will slump. A light spray of water will help the foam to stick slightly better. You can probably buy a lot of foam for the price of getting insulation blown in.

Is there any chance of accessing from above in the loft space?

Access from above would really help with the foam, as would making up a longer nozzle to help direct the foam where you need it.

Yes. I usually buy a couple of metres of polythene tube to fit the nozzle so I can inject over windows, doors etc with the can still upside down. Sacrificial, but it allows the job to be done properly.

 

[biskit]

I always knocked the outside skin down to gain another 6" of room, and just fit cut blocks and dpc up the end cavity.

 

[plug]

Possible to fill with vermiculite insulation?

 

[dickm]

Possible to fill with vermiculite insulation?

Certainly a thought, but not sure how to do it. Presumably needs blowing in with something, and you'd really need to have something along the bottom of the space still?

I think we'll probably go along the "drill holes and squirt foam" lines. Anyone got recommendation for the cheapest place to buy foam to go on a standard gun?

 

[Steve Maskery]

Screwfix?

 

[Austinisgreat]

Screwfix?

Seconded. Last time I bought some their own "value" or whatever expanding foam it was loads cheaper than "branded" foams.

HTH

Andrew

 

[Phil Pascoe]

Don't forget to 1/ damp down where you can, and 2/ warm the cans well before you start - you'll get much better expansion. If you put holes in specifically for the injection, it might pay to inject alternate holes and let the foam set before doing the other holes - the first lot setting will help stop the second lot blowing anything apart if happen to use too much ... which you probably will. DAMHIKT.

 

[dickm]

Thanks guys. The house is actually my daughter's, and son-in-law has gone ahead with the drill holes/inject foam option. Seems to have worked, but difficult to be sure if there are any gaps. Still, whatever gaps are left, it has to be better than the previous howling gale.