Filling gap at edges of window reveals

[JamieB3009]

Hello,

I had new windows fitted a couple of months ago. The old windows had some odd shaped trims on them so where the new windows have been fitted, there is a gap at the edge of the reveal. The window fitter filled these gaps with filler, but it has started to crack. I have raked it out and it would appear it probably cracked as theres nothing behind it to grab to. What would be the best method to fill these gaps and prevent future cracking? Would it be expanding foam and then filler on top? I was intending to use painters mate for the long thin gap down the side of the frame (existing silcone raked out).

Thanks & merry christmas!

See photos.

 

[opps]

Given that you are filling up to existing rockwool type insulation, I would lightly mist the insulation, apply making tape to protect the upvc and then spray in expanding foam. Once cured, cut back so that it is about 5mm below the surface. Then use a filler such as toupret tx110.

The pound shop sells small cans of expanding foam for 2 quid. Shake the can before use, and only use the can upside down. It will increase in volume by at least a factor of 4.

Place a bin bag under the can. after using it, some foam may drip out the end of the nozzle. After a while, press the nozzle, it will force propellant out and largely clear the nozzle. After a couple of days, the can may well be unusable.

 

[robinbanks]

After a couple of days, the can may well be unusable.

Aye, so it perhaps makes sense to go round the house and make a list of all the places it could be useful in and use the entire can up on filling any gaps one can find

 

[opps]

Aye, so it perhaps makes sense to go round the house and make a list of all the places it could be useful in and use the entire can up on filling any gaps one can find

If in any of those places, you are unable to invert the can, there are some cans that will work regardless of the orientation of the can

eg https://bond-it.co.uk/pu-foams-adhesives/mega-foam-expanding-foam/

I have no idea how much experience of working with expanding foam, so please don't think I am being condescending... I try to ensure that I have a can of PU foam cleaner with me whenever using PU foam

No Nonsense Foam Gun Cleaner 500ml - Screwfix

Order online at Screwfix.com. Use with gun adaptor to clean guns and spray nozzles. Removes all uncured PU foam. Suitable for gun and hand foam. Ready to use. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

Acetone however will work just as well. The cleaner is pretty much acetone in an aerosol

The spray of water before hand is important, it will help adhesion and increase curing times.

If the foam is still slightly soft, it has not yet cured. The inside will still be very, very sticky. If you start picking at the outer crust the cell size inside will/may become so big that it compromises the integrity of the foam (to a degree).

Expanding foam will not stick to polythene bags or polythene dust sheets. That is useful, if for example you are using the foam at dynamic joints such as where the bottom of the skirting meets a floating floor. If the polythene is sufficiently strong/thick, you will be able to pull the polythene out once the foam has cured.

The propellant released as the foam cures is flammable. It is also heavier than air. You would need to be using several cans at the same time for it to be an issue though.

 

[robinbanks]

Another tip with it; try not to make it too deep; fill big holes in stages. If the outside of a large ball of foam cures it tends to lock the solvent in somewhat for the inner, which then causes the cell structure to collapse before it sets. Same for filling up holes where all the surround is non-porous