Hello everyone, so I'm in the process of redecorating 2 back bedrooms of my house. The wall where it joins the window frame has always been a problem and been damp in areas with mould growing if it's not kept clean. I've removed the old painted over wallpaper and the area of damp/loose plaster. I expected to see a cavity but there seems to be brick closing the gap. My question is how best to finish/refill this joint to help prevent the damp which I presume is caused by a cold bridge. I was thinking expanding foam with filler to finish?