Could anyone help with a very annoying problem.
I recently decorated my dining room which has a five sided bay. I ripped out the very old window sill and made good the plater underneath that broke away with plaster board sat on top of plasterboard bonding (the whaite doughy stuff).
I made the window sill out of cill board (mdf pre coated) and stuck it down to the plasterboard with a polyurothene adhesive that is used to fix/glue buses together with. It's basically a very adhesive silicon sealant and certainly better than no nails.
All went well except every couple of weeks I get the paint cracking at the joints. I've used decorators filler. But they re-appear.
I'm thinking expansion and was going to drill through the would and screw the sill in place.
The paint is crown solo - it's very thick like emulsion, and i've given it about 4 sand and coats now...