A few weeks ago I had a leak in my roof which I had repaired. The problem started before the roof was fixed and I had water damage in the ceiling of one of the bedrooms. Well, I used my Ryobi recip saw today to cut out the damaged drywall (5ft x 4 ft) and install a new piece. The problem popped up when the new piece was installed. I noticed that some of the old drywall is visibly sagging lower than the new piece. It's way more than can be covered with a simple mud job. Any advice you could give would be welcome.
Ray V., Washington DC
The problem it seems is that the drywall ceiling is swollen. This is a very common. When the back of the drywall got wet from the roof leak, the water must have sat there for some time. As a result, that section of drywall has become deformed.
Unfortunately, there is no way to repair this except to cut out the bad section and replace it. You'll have to make the call as to whether it's just as easy to do the whole ceiling or to just widen the patch you are already working on.
Incidentally, if you are ever home when a leak occurs like that., the best think you can do is to grab the nearest screwdriver and go bang some holes in the drywall to let the water that is behind it drain out. If you do that, you'll typically get very little damage except for the minor patching you need to do to fill in those holes.