Recently, I had a small water leak above my kitchen which soaked a decent sized area of the kitchen ceiling drywall and ceiling joists. After discovering the leak, I removed the insulation, soaked up the water, and started air drying the space. A contractor visited and provided moisture analysis of the affected area and reassured me that the ceiling drywall and joists would be fine, as long as they continued to dry out.
Now, several days later, looking up at the ceiling in the kitchen, I can see moisture affected areas where the drywall was fastened to the ceiling joists. The fasteners look sunken in, the integrity of the drywall right under the studs is softer than its surroundings, and I think the drywall has sagged a little.
My first thought was to sister the ceiling joists and re-fasten the drywall using screws and plaster washers to help pull the dryall back into place, then apply mud to cover the new fasteners and the older, less structurally sound area.
Of course, the ceiling is painted, and my concern is that new plaster won't adhere properly to the ceiling without sanding, etc.
Any thoughts on how to re-establish strength in the ceiling drywall?