Warped window

[dale]

My brother in law has a problem with his sash windows - the bottom pane has warped inwards around 3 mills and can't be closed properly.

The windows were painted on the inside for a long time, but not the outside. He finally got around to painting the outside, and this may have caused the wood to warp (the window was new when I helped him install it).

I'm not sure how to fix it. Would forcing it into place and leaving it closed help bend it back over time, or is planing it a better solution?

[ThePope]

Would forcing it into place and leaving it closed help bend it back over time, or is planing it a better solution?

I'd try that first, jam an offcut of ply or fibro ect between the sash and the rebate, leave it for a week and see if it comes good.

[dale]

Thanks for that. I shall get him to do that and we'll see what happens.

[memoryman]

I've heard of fixing doors for "winds" and "cupping" by lying them out in the sun on a level surface for a few hours. Presumably this allows the moisture content to equalise, and probably you'd put the "cup" side down and let the weight of the window flatten it. I think forcing it into place with wedges will not work, as you need to wedge it past the neutral position, which I don't think you will be able to do. Just a suggestion.

[Skew ChiDAMN!!]

If the cupping was due to the outside being left raw while the inside was painted, planing would be a quick fix but odds are that after painting the outside it'll eventually move back as things equalise...

As rails'n'stiles for windows are generally fairly thick, I wouldn't hold my breath trying the sunlight method, although stripping the paint off and leaving it indoors for a few months would probably work. Well... might work. I wouldn't rely on it though.