It's sealing the corners time! Remember that caulk shouldn't be used on drywall joints. A drywall joint is created when two pieces of drywall are placed next to each other and the best way to attach them is with drywall tape and compound. In almost all cases, you need to apply drywall tape to the seams to reinforce the compound and keep it from crumbling out when dry.
Caulk shouldn't be used because the caulk would be adhering to gypsum powder. Yeah, there's a layer of paper, but there’s also dusty gypsum. There is nothing that really keeps gypsum adhering to itself, so trying to bond to it might only work for a little while. In my case the corners are tight and perfect, so I'm going to run a line of adhesive sealant down the seam where the wallpaper meets the wall. I love this Red Devil Celulon Adhesive Sealant! It exhibits strength, durability and adhesive characteristics superior to silicone and when cured it's mildew resistant.
The sealant is for the wallpaper seam. This sealant is no joke, so be careful not to get it on your fingers. I always use my fingers when smoothing caulk, but this stuff is strong!
The void in the ceiling from the roof window is filled in with wood and insulation. The contractor for some unknown reason nailed on that piece of flooring. These are professional roofers, so I'm not going to touch their work. I'm going to panel over the ceiling and act like this never happened. They did ask me if I wanted the ceiling re-wallpapered, so I'm wondering if they were just going to wallpaper over that.
Removing the wallpaper from the ceiling has been a nightmare! Nothing like the wall! It's in good shape, so I'm only going to seal it. I'm going to use Nippon Paint Fine Water Sealer. This sealer is recommended for ceilings and it's based on specially formulated acrylic. It is designed to provide maximum protection against alkali and moisture, enhancing the performance of the top coat. It's a water-based sealer that stops liquid water from entering the surface, but allows water vapor out.
I'm going to apply joint tape to the borders of the ceiling patch. I'm using mesh and it will strengthen the bond between the patch and the ceiling, reducing movement and helping to prevent future cracks. Joint compound will stick to any rough surface. If the surface is glossy, you'll need to sand it. I'm using a synthetic resign compound as a bed for the tape.
First coat complete. Joint compound dry times are all different, so read the bag. This brand dries in 2 hours. I let it dry for 24 and then sanded it.
Second coat! Don't cheap out on your skim coating tools. I bought a cheapo drywall squeegee and the rubber on the tip starting coming off in little bits. Next up is sanding and sealing with a sealer/primer.