Sagging Ceiling Sheetrock

[spence]

Not sure where to post sheetrock questions. I'm looking at a remodel on a home I'm trying to buy. The cielings are wavy as hell. My guess is that it has trusses at 24" center and 1/2" sheetrock. Possibly even no attic insulation. If I tear the ceiling sheetrock all out I would have to put 5/8 rock back in because of the 24" centers, but then I would have to trim the tops of the wall sheetrock to slip the 5/8" in. That seems like a lot of work.
Is there a simpler way to solve the problem? Maybe I should screw furring strips to the ceiling and then screw new sheetrock to the furring strips, thus solving the problem of 24" centers. Or maybe I should just paint it and forget about it.
I have been told that if you paint the sheetrock with oil based primer it won't sag on 24" centers.

Any ideas?

[giddonah]

Why not just cut the 5/8" to fit against the wall instead of trimming the walls? You won't be able to tell once it's spackled and painted. I think the furring strips would be more work than you need to do. Never heard of the oil based paint thing, but that doesn't mean it isn't true.

[spence]

Thanks, that's a good idea. One advantage of doing the furring strips is not having to mess with any existing insulation that might be up there. Less haul off.

[giddonah]

If the ceilings are tall enough that 1" won't matter, then that's a possibility. If it's loose insulation, then you really would have a mess. with bats though, it might not be that big of a problem. If there are ceiling lights though, the extra 1" will require you to add extenders to the boxes. One more thing to consider.

[spence]

Good points. Thanks.