Apologies if this is the wrong community.
I have a house renovation project ongoing. Before winter I fitted European oak internal windowsills which over winter have badly warped (cupped and bowed). I’ll have to replace them so would be grateful of any advice as to how to stop new ones doing the same.
We were told that the wood was dried, and it was sanded and given several coats of Danish oil prior to fitting. I think they were glued in place with PU adhesive, but I didn’t do that but so am not sure.
The winter was relatively hard with dramatic changes of humidity and temperature in the unheated house, if that would have an effect. One window sill was not fitted but was left in the house all the time. It’s still in perfect condition. The sills are approximately 20mm thick and 200mm deep. The warping is in the order of 5-10mm.
Any advice as to what went wrong or how to prevent it happening again would be much appreciated as it’s heartbreaking seeing that much oak being spoilt.
Update, for what it’s worth.
Over summer, and after getting the place properly watertight the wood gradually straightened out. It’s not perfect but getting there and all bay one of the sills are pretty much acceptable.
I think the problem was that the underside of the wood was more humid than the top side which could dry out.
Lessons are: don’t expose wood to repeated large changes in temp and humidity over a prolonged period. If you do however, be patient, there’s a chance that it will fix itself.
So glad I didn’t panic and replace them.