Warped double glazing draught proofing suggestions

[Steamshovelmama]

Hi,
I'm in the middle of completely redecorating and fixing a bedroom in a house built in 1950. The room has some very old double glazing (minimum 15 years which is when we bought it, probably a fair bit older). The guy who owned the house before us was a general builder/painter/decorator and it seems to be a case of the cobbler's children going barefoot, as everything he did to the house was the fastest, cheapest and most bodged!

Anyway, the room's window - a picture window with a single UPVC side hung casement to the right - has been draughty for some time. I have filled the area around the frame with expandable filler, changed the friction stays so the casement closes correctly and sealed around the frame. All of this has helped a great deal but I am stuck with a narrow gap where the casement side does not fit snugly against the frame (the side opposite the lock, next to the outer frame). You can actually see a thin sliver of daylight if you stand at the right angle! This does not seem to be the hinges. I suspect the original windows were partially load bearing which was ignored when the UPVC was fitted so the frame is bowing outward slightly.

Replacing the windows is out of the question at the moment! So I'm looking for a recommendation for something that will stop the wind whistling through the gap between the casement and the frame. I assume some sort of compression seal would help but does anyone know any good tips or tricks?

 

[crank39]

Tall windows tend to suffer from this a lot, one way is to remove the frame fixing in the middle of that side if the is one, there might only be 2 if it's a short window, if you've not decorated yet that's good, get a wide bolster chisel and lever a gap open in the middle of the frame between the frame and plaster, about 5mm should do it and knock,in a sliver of wood as a packer, this obviously bows the frame out so it meets the sash/opener frame so hopefully you'll get gasket compression that way.

The professional way is to fit 'closing wedges', one half on the frame, the other on the sash and as you close the window they rub on each other and pull the middle of the sash in tight against the gasket, you will however feel it binding as it closes but that's the nature of the beast unfortunately

 

[Steamshovelmama]

Thanks very much for that. That's a really helpful explanation. No, I haven't decorated yet - want to get all the potentially messy (or damaging!) work done first.

I'll have a go at inserting a packer. I did have doubts about a compression seal as the gap isn't uniform all the way down, but wider in the centre than at the top or bottom.