Covering expanding PU foam around windows and doors

[David W E Roberts]

On Linux at the moment - so different news server.

I have finally filled all the gaps around the doors and windows with expanding PU foam and now need to finish off.

It is easy(ish) to cut the foam back to flush with the frames but much more difficult to create a (say) 2mm rebate for flexible filler or (in the case of some of the larger gaps around the door frames (blush) to point up with mortar.

I have looked for advice on painting over PU foam, and the general advice (including some on this NG) seems to be that you should do more than just paint.

However

"Tooling: cured foam can easily be cut, sawn, sanded, plastered or painted. " So is it OK to paint over foam with an external masonry paint or should it really be cut back intop the recess and covered with something else?

I am going to use flexible filler around the windows, but I am looking for an easier way to finish off the doors.

Cheers

Dave R

[Tim Watts]

How I did it:

Small gap width, 2-7mm - I managed to scrape out the foam with a small screwdriver to about 3mm or so rebate, then filled with acrylic sealant.

The wide gap as the bottom I cut flush and stuck from uPVC trim on.

[Jim K]

piece of wood with "a few" nails through the end, protruding as far as you want the rebate deep. cut cured foam flush to frames (I find it simplest with a wide chisel or 1inch filling knife) then abrade with your "scratching stick" to make the rebate?

Jim K

[David WE Roberts]

thanks, but the wall by the door is out of true so I have a gap that is too wide (and irregular) to cover with trim. I need to paint it to match the wall and so hide my shame :-( The windows are no problem thanks to the dummy frames they were built around. So I need to know if I can paint straight over foam or if it needs something more to cover it. The widest part is very wide to cover with filler so it would be nicer to put some render on where it is not flush with the wall.

Just exploring options

Cheers

Dave R

[stuart noble]

Even if you could paint it, the texture of foam is never going to match the masonry. It turns bright orange after a while, which might show through the paintwork, and (I think) breaks up under UV light. I'd cut it back to about 10mm below the surface (a broken hacksaw blade is quite useful for this), and fill with a sand/cement/pva mortar.