Drywall Ceiling - Which Thickness ?

typically, 5/8" is used on ceilings because it is stiffer and will be flatter. however, i have seen 1/2" used on ceilings successfully if the joists are 16" on center or lesser.

Increased fire blocking. less sagging and heavier trying to put up.

Thanks. My Joists are spaced 16 in OC and I am planning on applying the wallboard directly on the joists. From what i've seen in the rest of the house , the Joists may not be level. If the 5/8 will help to correct some of the problem, I'll go for it then. Is there any advantage in stargering the joints? or just apply parpendicular to the joists symmetrically ?

Thanks.

Most building codes require 5/8" for flame resistance.

There are 1/2" boards specifically made for ceilings, such as SHEETROCK=AE Brand 1/2" Interior Gypsum Ceiling Panels

I would suggest that if you really have joist that are not level, 5/8 will not fix that, you need to shim the joist to get it properly flat.

Do you mean to install shims between the joist and drywall as needed ?

Sort of.

I had can lights put in my kitchen this week (late '50's split level). The ceiling was plaster OVER drywall. It was 7/8" thick. They also used chicken wire in the corners. Just thought I'd share...

You can also use 1/2" high density board. Hand trowling will help hide any defects as well and looks more professional in my opinion.