Fixing a UPVC window

[Theo]

I have a UPVC window which appears to not be attached to the frame along one edge. When the wind blows the top of the window moves outward[1] by about

3-5mm and there's a moaning draught through the gap (there's also a silicone seal that has broken due to the movement).

I could stuff in more silicone, but is there a better way to more securely anchor the window? The outside is inaccessible and I don't really want to take the frame or glass out (although the glazing panel isn't in the best of condition, it's OK for the moment). I don't know what's behind it but assume a timber frame (there's no masonry nearby).

Any suggestions what I should do? Maybe there's something I could squirt into the gap? I have some expanding foam, but I'd like to prevent the window moving first of all, ahead of filling the gap.

Thanks Theo

[1] due to the prevailing wind, the window is in a low pressure spot and gets pulled outwards

[Steve Walker]

Expanding foam will both fill the gap and stick to all surfaces, so anchoring the window. Many (less than good) installers rely upon it alone instead of properly securing the frames to the brickwork.

[Martin Brown]

Expanding foam can expand too much and is a crude solution.

Space filling PU high tack glue is probably better suited to the job.

Wear gloves! It sticks anything to everything very aggressively.

[Jeff Layman]

I assume it's a tilt and turn window if the top moves outwards (or is it the glass which is moving within the frame? If so, that's a different issue). Don't PVC windows have multi-locking points? Is it possible that one or more at the top have come loose, or the handle isn't turning the locking mechanism far enough to fully engage the lock?

Anything useful here:

[Theo]

No, it's a fixed pane (one part at the end is casement, but that's not affected). The whole glass and UPVC frame moves in the wind, ie it isn't anchored to the surrounding wall.

Theo

[The Natural Philosopher]

Actually a foaming glue like gorilla glue applied to a large surface area is far better than screwing a frame in a few places to an uncertain matrix

And it seals as well.

[The Natural Philosopher]

Gorilla glue or any strong foaming style adhesive

Even redoing any caulking or frame sealer will probably work

[Theo]

Thanks. They all seem to use different words, but do you mean something like Sikaflex EBT+ ?

There are also 'hybrid' polymer sealants claiming to offer the best of silicone and PU, eg Everbuild EB25. Are they better than straight PU?

Is it possible to shape it into a bead like silicone, or does it end up too sticky? (Not sure if the hybrid versions are less sticky, but they set faster)

I also wonder whether it's better to have something rigid to prevent the window moving, or something flexible to allow the window to move but keep the gap sealed...

(I have no idea how big the gap behind the frame actually is)

Theo

[RJH]

I'm not sure, but I'd guess Martin's talking about one of the low expansion 'fixing' types.

It ends up like solid foam, and you can only work it when dry.

I'd strongly recommend a gun - it'll allow you accurately control the volume the foam, and allow a relatively think bead if you need it. It'll also keep the foam ready for use again - I keep mine for up to a year at a time and it's always been fine. But the guns are quite pricey, and you'll need a tin of acetone to clean it between cartridges.

Rigid - it was supposed to be screwed into the wall in the first place.

Another case for foam - many of my windows have gaping holes behind the facia trims where the openings have been hacked away over the years. The bay sash windows alone took 4 whole tins of high expansion foam. Filling them with foam gives a measureable improvement to surface temperatures. What that means in the scheme of insulation I'm not sure.

[Andrew]

You need to use foaming PU adhesive NOT expanding foam, which will join the top of the frame to the lintel above it.

If the wind can bow the frame out at the top you can push it out and get the nozzle in there.

uPVC window frames tend not to be mechanically fixed at the top, and rely on internal streghtening inside the uPVC profile to provide stiffening. In the past (?still done) a metal channel section would be inserted and if the window is load bearing I think this is still done, but these days a plastic channel moulding is inserted inside the boxy uPVC frame for extra strength before the sections are cut and welded by the computer-controlled rig.

[Brian]

From your description, you need to remove the glass to do a proper job. If not, the whole inner frame could drop out.

Generally, this isn?t too difficult unless the glass is large and heavy.

There is usually a narrow rubber sealing strip next to the glass, 4 bits. Remove carefully noting where there where.

With someone holding the glass, remove the 4 beads, they should unclip.

There will probably be some spacers under the glass, note where they are.

Carefully lift the glass out, the spacers may drop out so retrieve them.

You should now be able to fix the inner frame to the outer frame from the inside. You can get special frame fixings - long screws with long Rawl type plugs but self tapping screws may do the job if the outer frame is secure. Check the heads are clear of where the glass fits and fill any gaps will sealer before pulling the inner frame into position.

Put the spaces back, the glass, have someone hold it. Next the beads. Finally the seals.

[Andrew]

I thought you said it was bowing at the top, where most fitters would not fix because it means drilling into a lintel.

If the sides are moving then it means that they probably glued the whole frame in with foaming PU adhesive and not bothered with any frame anchors or 'concrete' screws or other mechanical fixing.

Can you remove the fixed pane from the inside and then you will soon see if there are any screw heads ?.

[#Paul]

I fixed a similar 'not closing on one edge' problem recently by simply lubricating the hinge mechanism; the window was hard to get to and when - as was typically necessary - it was pulled closed from an angle, the hinge-edge got stuck slightly out from the frame leaving a gap.

#Paul

[Theo]

Hmm, that's an interesting thought because the gasketry isn't in such great shape, so it would be good to replace that too. Or, if it's not so hard, maybe change the glazing panels as well.

But there's no beads, just a UPVC frame well sealed to the wall:

However, further investigation reveals there *are* beads, but they're outside: That would be a scaffolding job to access. I guess that means it's not possible to take the panels out from the inside without destroying the frame?

Theo

[Theo]

It is a timber wall, but I suppose there could be a steel lintel in there - the span is quite wide. It's just the top moving, not the sides or base. That could just be where the amount of flexure is greatest though.

Not easily, see my other post.

Theo

[Andy Burns]

if there's an opener at the other end, can you see any screws there at all?

[Theo]

On the casement parts that open, about 600mm square, there's 2 screws in the side, one screw in the bottom near the hinge, and none at the top. There are additionally screws for the hinge sliders and locking bosses - I can't be sure if they go into the surround or not without taking them out.

Theo