Ok so this is niche. I’m renovating my old sash windows as over 140 years of bodges (silicon bathroom sealant for filling cracks anyone? Sheesh!) have finally taken their toll. The windows are in good condition but the mix of horse hair mixed lime mortar, cement and foam have given up the ghost. I’ve got some proper sand mastic for the sealing but need advice on which is the best low expansion foam to use to fill the gap between the frame and the exterior stonework?

So what does the hive mind recommend? Soudal low expansion roam and a professional gun seem to be the way forward but any experience and advice greatly appreciated.

Thanks

Sanny

Not used that Soudal foam but the rest of their products are good. Do however get a Fischer foam gun, they are super easy to control and are much better than the budget ones from Screwfix etc.

That is the gun I am getting! Happy days!

use Everbuild Dryfix, it’s meant for sticking plasterboard to bare masonry so it stops expanding after a few minutes. skoosh some water in to help the bond and make sure you only fill the very front of the space or you will end up with cords and weights getting stuck.

Soudal low expansion roam and a professional gun seem to be the way forward but any experience and advice greatly appreciated

I used quite a bit of this to stick the insulation in our camper van.

No problem at all with the Soudal low expansion foam – very predictable and controllable, but I think it’s the gun that makes the difference.

It’s all a far cry from the mad and messy world of aerosol can foam.

Get a can of gun cleaner to run through it when you’ve finished the job. (I used to leave the foam can on the gun for a few days at a time and it was OK).

Don’t get it on anything you don’t want made sticky – best thing for cleanup *before* it goes off is Everbuild Wonder Wipes.

Something breathable would be good , maybe horse hair lime mortar or modern horse hair replacement. With old properties its always 3 rules breathable, breathable, breathable. Low expanding foam is just another bodge.

It’s all a far cry from the mad and messy world of aerosol can foam.

I made a stable door for a lady about 5 years ago. While fitting it I used that horrendous stuff and managed to get it stuck in her dogs fur.

Still with her mind. 😂