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Old 03-09-2009, 08:31 AM   #1
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Question about greenboard on ceiling


I was reading a drywall 'how-to' book, in advance of my first drywalling project (guest bathroom), and came across a surprising piece of advice that I wanted to check with the experts here.

This guy said not to use 1/2" greenboard on a ceiling unless the joists are 12" o.c. or less. He didn't say why, but I assume he's claiming it would sag. He says to use 5/8" greenboard if joists are more than 12" o.c.

Really? My joists are 16" o.c. Has anyone had a problem with 1/2" greenboard in that application?

(I realize some would say there's no need or benefit to putting greenboard on the ceiling, but greenboard is what I have already bought and it's 1/2". Just wondering if I need to get something different.)

Thanks for any words of experience anyone has on this.

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Old 03-09-2009, 09:01 AM   #2
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Question about greenboard on ceiling


16" OC should be fine for 1/2", it MAY sag over time, and almost certainly would if it was 24" OC.
personally, i'd use 5/8" to avoid it, but if you have 1/2" already, and you're at 16" OC, i wouldn't sweat it too much.
(although others here may disagree.)
maybe mount some blocks between the joists for added support if it worries you too much?

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Old 03-09-2009, 09:20 AM   #3
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Question about greenboard on ceiling


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maybe mount some blocks between the joists for added support if it worries you too much?

DM
Unfortunately I've already got the ceiling insulation up, so I'd have to undo that to add blocks.

Could still do that though. Let me see what others recommend.
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Old 03-09-2009, 09:30 AM   #4
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Question about greenboard on ceiling


furring strips is another option, though un-necessary IMHO... i still think you'd be fine with your way.

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Old 03-09-2009, 09:59 AM   #5
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Question about greenboard on ceiling


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furring strips is another option, though un-necessary IMHO... i still think you'd be fine with your way.

DM
Drywall installed on ceilings with 24" OC joists need to be 5/8" If you want to use 1/2" drywall then furring straps are recommended every 16" OC... SO...16" OC with 1/2" will not sag and is withing manufacturer's guidelines.
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Old 03-09-2009, 10:04 AM   #6
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Question about greenboard on ceiling


may as well add, around here, you need 5/8" Fire-X for ceilings.....

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Old 03-09-2009, 10:09 AM   #7
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Question about greenboard on ceiling


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may as well add, around here, you need 5/8" Fire-X for ceilings.....

DM
For condos, apartments and garages yes... but where do you live that this is always the case?
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Old 03-09-2009, 10:56 AM   #8
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Question about greenboard on ceiling


i just do what the inspector tells me to! lol
where are YOU from? my location is right there under my avatar!

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Old 03-09-2009, 11:13 AM   #9
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Question about greenboard on ceiling


Quote:
Originally Posted by RDS View Post
I was reading a drywall 'how-to' book, in advance of my first drywalling project (guest bathroom), and came across a surprising piece of advice that I wanted to check with the experts here.

This guy said not to use 1/2" greenboard on a ceiling unless the joists are 12" o.c. or less. He didn't say why, but I assume he's claiming it would sag. He says to use 5/8" greenboard if joists are more than 12" o.c.

Really? My joists are 16" o.c. Has anyone had a problem with 1/2" greenboard in that application?

(I realize some would say there's no need or benefit to putting greenboard on the ceiling, but greenboard is what I have already bought and it's 1/2". Just wondering if I need to get something different.)

Thanks for any words of experience anyone has on this.
This is per manufacturer installation instructions.

It pertains specifically to MR/Green board. This board is not quite as rigdid as standard sheetrock. Thus, it requires additional screw placement for installation on ceilings.

So to follow this advice, you should either install additional framing (strapping) at 12" O.C. on the ceiling, or use 5/8" MR board.

Good luck.
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Old 03-09-2009, 11:44 AM   #10
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Question about greenboard on ceiling


Have you checked with your local inspector? Green board is now illegal for bathrooms in some locations.
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Old 03-09-2009, 12:02 PM   #11
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Question about greenboard on ceiling


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Have you checked with your local inspector? Green board is now illegal for bathrooms in some locations.
Not for bathroom ceilings and non-tub wall locations, just for shower/tub/wet areas.
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Old 03-09-2009, 12:21 PM   #12
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Question about greenboard on ceiling


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Have you checked with your local inspector? Green board is now illegal for bathrooms in some locations.
Good point. Yes, he made a point of telling me there's no greenboard allowed around the tub (I'm tiling over Durock there anyway) but that it's OK in the rest of the room.

What Atlantic said made up my mind, I think. I appreciate DM's confidence that what I have would be OK, but I think given those manufacterers' specs, I'll get something different -- particularly since, upon re-checking my math, I now realize I'm short a couple of sheets of drywall anyway.

5/8" greenboard is a special-order product, but if 1/2" regular drywall is rigid enough for ceilings with 16-inch centers, I think I'll just get some of that for the ceiling and save the greenboard for the walls. (The regular is also available in ten-foot lengths at my local store, which would make my life easier when it comes to taping.) I'll make sure the inspector's OK with regular on the ceilings, though. If he's not, then I guess I'll special-order some 5/8" greenboard.

(I don't want to add strapping -- wouldn't that mean I'd have to reinstall and/or add extenders to the electrical boxes, exhaust fans etc. on the ceiling? Since I need to buy more drywall anyway, I'm thinking I might as well get something that'll work with the framing I have, and save myself the bother of adding strapping.)

I appreciate everyone's advice, and if this new course of action seems unwise to anyone, please weigh in! I won't start the work til next weekend.
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Old 03-09-2009, 12:32 PM   #13
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Question about greenboard on ceiling


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(I don't want to add strapping -- wouldn't that mean I'd have to reinstall and/or add extenders to the electrical boxes, exhaust fans etc. on the ceiling? Since I need to buy more drywall anyway, I'm thinking I might as well get something that'll work with the framing I have, and save myself the bother of adding strapping.)
You should be able to move the lighting and exhaust vent unit downward, to compensate for adding the strapping (thickness) - if the ceiling is currently opened up. If you are set on not installing the strapping at 12" OC, you can use standard 5/8" Sheetrock, rather than MR on the ceiling.

You see - once you paint the ceiling using mold/mildew resistant paint/primer/or additive, the material will be sealed from moisture vapor. That is all that your ceiling should be experiencing in the future (just vapor, not direct water/moisture) especially since you have an exhaust fan. If you are planning on deluging your ceiling with water and direct moisture, I suggest that you change your bathing habits.

Installing MR board on the ceiling is actually overkill, based on the facts that I just listed.

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I appreciate everyone's advice, and if this new course of action seems unwise to anyone, please weigh in! I won't start the work til next weekend.
I tell you this from industry experience, not something that I am guessing about, or, based on what someone has told me.
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Old 03-09-2009, 12:58 PM   #14
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Question about greenboard on ceiling


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you can use standard 5/8" Sheetrock, rather than MR on the ceiling.
But not 1/2"? It matters only because I can readily get the 1/2" in ten-foot lengths, whereas the 5/8" I would have to special-order in that length. It would push the work back a weekend. Not a huge deal, and I'll do it if it's necessary. Is it?

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Installing MR board on the ceiling is actually overkill, based on the facts that I just listed.
Good, that's what I thought. The ceiling is well out of splash range, the fan is powerful, and it's a guest bath anyway so even the steam it's exposed to will be limited.

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I tell you this from industry experience, not something that I am guessing about, or, based on what someone has told me.
Yep, I realize that, and thanks again.
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Old 03-09-2009, 01:13 PM   #15
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Question about greenboard on ceiling


1/2" standard GWB (Gypsum Wall Board) will be fine on the ceiling.

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