Took down ceilings in a room on the second floor and it looks like they are 1/2”. House was built in 1983, but I thought all ceilings were supposed to be 5/8”? Joists are spaced 24” o.c., so I figured 5/8” would be best to prevent sagging.

If 1/2” is used, possible to replace with 5/8”? Space between joist and stop of room walls looks like 5/8” would fit. Or should I just replace with 1/2”?

2 Answers 2


I would replace the ceiling drywall with 5/8" material because it is much better suited for your ceiling joist spacing of 24" than would be 1/2" material.

There is no real reason that the ceiling drywall has to extend out to be over the drywall that is on the walls. The wall material can help support the ceiling material if it does extend out over the wall drywall. But if your ceiling joists have backing lumber between the joists at the ends and there is joist exposure along the walls parallel to the joists that can have screws driven through the 5/8" ceiling drywall into the joists and backing lumber then the only real need is to bring the new drywall up close to the wall material.

New taping joints along the ceiling to wall corners should easily make for a clean finished corner despite not having the ceiling drywall tuck over the wall drywall.

  • I didn’t even think that they didn’t need to fit in the gap. However, I’ve already bought an entire pallet of 1/2” sag-resistant drywall. I’m going to install blocking between the joists for more screwing space. That coupled with its lightweight, screws instead of nails and occasional use of adhesive, I doubt anything will sag. The insulation batts will also rest on the blocks, so that’s even less weight on the panels.
    – pstatix
    Nov 29, 2020 at 18:42

Ceiling thickness is partially about fire rating and partially about rigidity. I don't think 5/8 became standard until the late 90s? You can do 1/2" but it needs to be type C.

  • What it is Type C? Would I just need to match the standard fo when the house was built? Or should I bring it up to current standard?
    – pstatix
    Nov 27, 2020 at 23:00
  • If you are already taking down the ceiling I'd go with 5/8" - you'll need to adjust any pot lights lower. I'd probably also add roxul sound insulation to the joist cavities if there is a floor above. If there is attic above I imagine you have a vapor barrier (depends on climate zone). Why are you taking down the ceiling? Nov 27, 2020 at 23:04
  • they had no ceiling lights and were also stomped ceilings with painted joint compound. So I figured I’d replace the texture and add pot lights. My concern is the 5/8” might not fit in the gap between the joists and the top of the wall.
    – pstatix
    Nov 27, 2020 at 23:06
  • Our second home was built in '73 and all walls were 5/8. Even then they knew how to build it good. It makes a big difference. Nov 27, 2020 at 23:57
  • @TedMittelstaedt they are so close in size, just can’t tell if it’s 1/2” or 5/8”
    – pstatix
    Nov 28, 2020 at 0:07

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