greenboard or cement board?

**amys** · 08-11-2005, 08:43 AM

Hi, I am looking for some advice. I am wondering whether to use 'greenboard' or cement backerboard for the ceiling above the fiberglass tub/shower unit in the bathroom my husband and I are remodeling. Our ceilings are only ~6'6" tall, so the ceiling material will get a lot of moisture, maybe even some splashing, though we're both under 5'6" tall

. Would greenboard be adequate, or is water*proof* material necessary? If backerboard is the only good option, is it possible to join the seams as would be done with greenboard/drywall to make a decent-looking ceiling? Or could we put a coat of waterproof joint compound over the whole surface of the backerboard?

Also, would you recommend greenboard in general for the bathroom, or is normal drywall adequate everywhere else (walls around sink, toilet, etc)?

Thanks for your advice!!
Amy

**thezster** · 08-11-2005, 10:24 AM

6ft 6inches high? That doesn't meet code where I live.... Maybe folks are shorter where you come from.....

Greenboard is not that much more expensive than plain old drywall..... splurge a couple of bucks and buy it for the bathroom...

As for cementboard seams.... you should join seams with cementboard joint seaming material.... and it comes out nice... For the ceiling - I would put up cementboard "backwards"... smooth side facing you.... it should finish nicely...

**jimbo** · 08-11-2005, 01:29 PM

Cement board is generally used as a substrate for tile. I have not seen it done as a finished surface, but no reason why it could not. I would check over on the johnbridge.com tile forum for advice on how to smooth coat it.

**jadnashua** · 08-11-2005, 04:06 PM

Greenboard is usually not allowed on a ceiling unless it is supported at 12" rather than the 16" of normal joist spacing (16" spacing is okay on a wall). Regualy drywall, properly painted is sufficient for all of your bathroom except behind tile in the shower/tub area. There, you should use cbu (cement backer unit) such as Hardibacker or one of the other brands. My unprofessional opinion. Go to the manufacturer's website and you'll be able to verify my comments. I highly recommend www.johnbridge.com

**amys** · 08-11-2005, 08:49 PM

Thanks for your kind and helpful replies. We'll take this input into consideration and hopefully have a functional ceiling surface in the end! Thanks again.

**plumguy** · 08-11-2005, 09:05 PM

Regular sheetrock or blueboard is fine on the ceiling. You should be more concerned on the paint that you choose. Make sure you use a high quality bathroom paint, I used Zinnser(sp) years ago on my bath remodels and it was excellent. Not only was it scrubbale but it also very durable and long lasting.

alhurley · 08-14-2005, 06:47 PM

that would be Zinsser Perma-White, right? Excellent choice - have used it myself.

**plumguy** · 08-14-2005, 07:07 PM

That's correct!!

**decisions, decisions!** · 09-02-2005, 09:45 AM

Where do you find Zinsser Perma-White paint-I've never heard of it? Thanks!

alhurley · 09-02-2005, 04:45 PM

try the boxes - they carry some Zinsser stuff. If not, try a paint store - shouldn't be that hard to find. Or call Zinsser and they may be able to tell you.

**toolaholic** · 09-22-2005, 09:08 PM

is wrong . use 5/8" reg sheet rock

**BellevuePaul** · 09-23-2005, 02:53 AM

Interesting comment about 16" centers for normal ceilings...it seems like I'd heard that many truss built houses might even have 24" now.

Anyway, I was wondering if the posters could explain *why* greenboard wouldn't be a good idea for a ceiling, in particular right inside a show surround.

Assuming one doesn't do that, and uses regular sheetrock (5/8 I guess...is 1/2 out of the question for ceilings? I heard sometimes 3/8" is used to reduce weight on ceilings...) do people typically use something like RedGuard to block moisture?

The Zinsser that people are talking about, can that be tinted, or are people using it as a primer, or does everyone out there have super white bathrooms? :-)

**jimbo** · 09-23-2005, 07:27 AM

I think code might require 1/2" min, thickness of drywall, but check locally.

I believe the consensus was that cement board is probably not recommended for ceilings. If it is uses, proper fastener pattern must be observed. I do agree that it is probaly over kill. I do think greenboard is recommended. If there is code against that, please help me out on this!

The PermaWhite is a finish coat. I guess 99% of bathroom ceilings are white. Check with your paint store as to whether it can be tinted.

As with all new drywall, a first coat of PVA primer is the best, and I would follow this with a coat of the best general purpose undercoat your local store carries. Any paint store or box store will have something. Then apply your topcoat. I prefer gloss in bath and kitchen, but a good semi-gloss will certainly perform well.

On the RedGard, I don't think it goes on smooth enough to be an undercoat for paint.

**finnegan** · 09-23-2005, 11:17 AM

3/8" is generally used only as a veneer over existing plaster or drywall. 1/2" is code except when 5/8" is needed for fire rating. Greenboard is fine on 12" centers for a ceiling. If you have 24" or 16" oc, you can strap the ceiling, which is a good idea anyway. 1/2" drywall is fine for a painted shower ceiling.

**jadnashua** · 09-24-2005, 01:29 PM

Greenboard's surface isn't as strong as normal drywall...I'm told it will sag noticeably if not supported at 12" on a ceiling after time. Also, regular drywall is much stronger along its length than it is across the width. So, if you have a choice, install it horizontal on walls and across the joists on a ceiling, adding blocking as required.