Very significant and I would be mega interested in a thermal image of the wall in question, where are you?

It is usually pretty windy in the floor void which is connected to outside in several ways including via the loft!

I have taken some stills, not sure how much they convey, the video with motion helps to understand what you are looking at. Can they be attached to the thread? If so I will need to re-size them first I think.

Upload the video to Youtube and copy the link into here. Works for me.

But they still don't get used!

If removing skirting boards then drill holes big enough for the nozel of a PU foam gun and give a little squirt every 80mm-100mm this could also be done at top of room and covered with coving. Dont squeeze in to much foam as it could push the plasterboard of the wall.

Thanks for the ideas everyone. Downstairs will be ok to fill at the bottom as most of the skirting has already been replaced and most is now removable via screws. Some sealing has been done, but wont be complete since I hadn't quite realised the importance. Coving already downstairs, the plaster type which is not easy to remove, need to experiment there. Upstairs is the reverse, I think I can fill the top from the loft, but the skirting has not been off. May be I should insulate between rafters upstairs as well - I did one bedroom (over garage!) last year, since the floor is chipboard one was enough.

I did mean floor joist, yes - it certainly will be a lot easier to not lift all the floors up. I think my next purchase is some polyurethane foam. A plan of action is slowly forming.

Andy

Posted By: andyman99Just been looking for an expanding foam with low expansion capabilities as I dont want to blow the plasterboard off the wall. Found Insta Stik Foam Grab, but it seems a bit expensive. Would "Everbuild Pinkgrip Dry Fix Drywall Adhesive" be suitable for this job?

Should work fine.
It will still expand a bit just less than the standard stuff. For a good bond it works best if you can wet the surfaces as you go along. I use a cheap plant sprayer for the job. Are you buying a foam gun and separate cans or the all in one? The reason I ask is that you have much more control with the dedicated guns than the all in one cans and the foam is a bit cheaper.

Made a start in the lounge, around the newish French doors. Uncovered this rather large hole direct into the cavity after cutting away small strip of the plaster - gales blowing in yesterday - these were put in by a window company so this is not the builders fault.

Nice work with the foam, I would masking tape newspaper to the floor first! or is that cardboard protection in the pic?

Try to ensure foam fully fills all gaps and cracks.

I used to very lightly mist with a house plant sprayer first to aid adhesion and setting before and after applying the foam.

I would clear a track 15 to 22 at the bottom and foam as you are doing ensuring that the foam goes both up behind the board a bit and below the floor.

No gaps or misses is the order of the day.

I reckon that you could publish this job in GBM -- I am happy ho help with that too.

Thanks, I will look for some suitable tube, it will enable me to ensure I get some foam up behind the board which is difficult with the gun alone. I also experimented in the loft yesterday, this is more straightforward in principal just squirting down the gap, but again getting into the corners was not possible and there were a few times when I got a burst of propellant only - health and safety advice taken on board. So I have ground floor skirting and loft space techneques pretty much worked out. I Just need to find the best/least intrusive way to sort the junction between ground floor ceiling and first floor. Would be nice to be able to work just from the bedrooms downwards, i will need to find a place where I can view the results from below to test different techniques.

Sheffield used to supply them in bags try another branch? It will work but beware wind can blow them about.

Continuing the investigative work, now at bedroom floor level, I have started sealing the base of the plasteboard behind the skirting board. All went well until I reached far RHS of the first bedroom and discovered gales blowing in. Investigating further I uncovered an I beam or RSJ? This takes the weight of the bedroom rear wall over the lounge. The lounge, for some reason, extends beyond the rest of the house and has horrid little flat roof to the rear. This RSJ is about 12/13ft long. By cutting holes in 2 bedrooms I have I think worked out the cross section, see below. From previous investigations of the flat roof, I am pretty sure that the wall at points "A" is not so good, and likely not sealed completely, but I dont have pictures of this. The void between the I beam and the Joist is quite a big and awkward area. All I can think of is to get some of the more expanding, expanding foam and try to seal this void at each end and perhaps in the middle (prior to checking over the suspect wall at a more suitable time). It is not easy to get access to the whole length of the RSJ (although possible I guess). Oh and also try to seal the gap along the botom of the skirting "B". And there is a 5mm gap under the RSJ to the lounge ceiling. I think I could only seal that from the flat roof side