fitting PCVu windows - foam and sealant

[sm_jamieson]

Standard method is to fill gaps around frame with expanding foam, then a frame sealant on the outside. But, what is the trick to foam the windows and leave the foam 5mm below the surface in order to receive a sensible sized bead of frame sealant ? AFAICS, the foam will overflow at least slightly and stick to the frame and bricks such that cutting it back will leave residue. You could tape / mask off the window frame OK, but this would be tricky for the bricks which do not present a contrinuous surface with the mortar beds etc. I don't want to stick on white cover strips which look crap. So whats the trick to doing this ? Cheers, Simon.

[Tim W]

sm_jamieson wibbled on Wednesday 13 January 2010 15:48

When I did mine, I tried to go easy on the foam, inserting the tip of the nozzle into the gap. I also foamed from both sides as the plaster was stripped back inside.

Obviously, try not to foam level with the frame as it will expend further.

But, if it does extrude outwards, I found that being semi gone off in this state, it didn't adhere so much to the bricks not did it get stuck to the front surface of the frame. Masking tape if practical will certainly protect the frame and the bricks from accidental contact and a fine wire brush (fine bronze coloured jobbies) can take most of the residue of a rough finished brick OK and a screwdriver can be used with care for minor cleanup (don't obviously do this on the face of uPVC)

After 24 hours, I used a screwdriver just to scrape back the foam so it was a few mm undercut and applied sealant - the latter I found vastly more fiddly as there's not much latitude for error nor using Fugenboys when you have rustic faced bricks!

[sm_jamieson]

Thanks for that. Luckily I have smooth bricks. I've also got a pro foam gun this time, and low expansion foam, so I can do a few tests and get used to how much the foam expands. Simon.

[Tim W]

sm_jamieson wibbled on Wednesday 13 January 2010 16:32

OK, because you can, use masking tape. Try to get the wet foam around

1/4-1/2" back from the final surface. That should make scraping back simple and not leave too big a gap to fill with sealant.

[Stuart Noble]

According to our DG fitter the foam gun is "the secret". He reckons you can tell a d-i-y job by the orange foam residue on the wall.

[Usenet Nutter]

But what if the d-i-y'er is using a Pro Gun?

[Stuart Noble]

He reckons it's more controllable because at least some of the expansion takes place before it leaves the gun

[JimK]

mmm... more like practice makes more perfect

OP - white spirit will help clean it off hands and frames whilst it's wet (unset) - though getting it off masonry could be interesting.

JimK