Rolly's Bathroom Remod

[eagle0001]

Hi all! I just joined the Forum. I appreciate all of the information exchanged by members and made available.

I am in the midst of a master bath remodel and have just read in several threads that greenboard on the ceiling is not a good idea for a variety of reasons. Unfortunately I glued & screwed 5/8" greenboard to the ceiling (joists are 24 o/c) before coming across the Forums. Note that I placed screws approx. every 6". Hence, a lot of screws for good support.

With the above in mind, should I tear it down and use regular drywall?

Good to be here.

[Toddman]

Welcome Rolly good to have you.

I'm not aware of the problems you're talking about so I'll leave that up to the other members to comment on. Although I think the ceiling joists need to be 16 o.c.

[cx]

Welcome, Rolly.

Yes.

Wouldn't hurt to add more ceiling joists while you have the ceiling open, but technically you can get by with 5/8ths" sheetrock unless you have a particularly heavy insulation load above or particularly heavy tile.

My opinion; worth price charged.

[jadnashua]

The issue, as I understand it, is that greenboard is not as stiff as drywall when installed properly, and can sag when not supported properly on a ceiling. This is a function of the paper, the gypsum helps some, but the paper bonded to it is what does most of the stiffness. A call to the manufacturer or a check of their website might shed some light on this. 5/8" stuff is stronger, but on 1/2" stuff, the recommended spacing on a ceiling (I've heard - check) is 12", not 24". the quantity of screws/nails won't help between the supports, only along them.

[lyonkster]

FWIW, in my jurisdiction as well as in some others in CA, greenboard is prohibited outright from ceiling usage, joist spacing be d@mned... So you might also check if your local codes allow it.

[HooKooDoo Ku]

I seem to recall that there was some sort of issue where moisture can build up behind the drywall to the point it eventually collapses, and that that is the reason some jurisdictions now ban it outright in ceiling usage.

Think about it, the green cover is supposed to provide a moisture barrier. If the panel is sitting on the ceiling and moisture gets in the gypsum from above the panel, gravity pulls it down toward the moisture barrier leaving it no place to go. At least that is my guess. If you google "green board on the ceiling problems" you'll get lots of hits.

To me, it sounds like a tear out and redo. Only other option I can think of is if you can get to the ceiling and add a moisture barrier to the back side of the green board, and then cover the green board with something else (say a layer of CBU), then moisture shouldn't reach the green board and the CBU should protect the tile/ceiling bond (so that even if the green board disintegrated behind the CBU, the tile would still be fine). But now I'm just trying to think on my feet (so I don't KNOW what I'm talking about).

Sounds easier to tear out and start over.

[eagle0001]

Thanks for the replies and welcoming me to the Forums.

Considering the responses I received, I've decided to tear down the greenboard and replace with 5/8th sheetrock. Questions....

1) Being that my ceiling joists are 24" o/c, would it be most advisable to add more support for the sheetrock?

2) If the answer to question 1 is 'yes', please advise on best method to accomplish. (e.g., reduce spacing to 12" o/c by adding 2x4, or other, in between joists)

Many thanks!

[eagle0001]

Hi all! I am about to install the substrate underlayment in a bathroom remodel and have the following question:

Can new framing (i.e., knee wall/half wall, etc) and the shower curb be fastened on top of the new substrate underlayment or must it be fastened on top of the subfloor prior to installing the substrate underlayment? Hence, the substrate underlayment should be installed around any new framing.

Thanks in advance!

[bbcamp]

It can be installed on top, but I see no benefit. You would be trading a few straight cuts for drilling a bunch of holes. Cuts are easier. And, there is always the possibility of cracking a tile, plus you made changing out the floor harder for the next guy.

[eagle0001]

Thanks for the reply Bob. I need to correct my question though...I meant to say "underlayment", not "substrate." I'm so sorry.

Here's more info on my remod...I installed new 3/4" ply subfloor and on top of that I intend to install 1/2" ply, which I, in error, referred to as the "substrate". That being said, can I install new framing and the shower curb on top of the new "underlayment"?

Thanks again!

[cx]

Rolly, it'll help if you'll ask all your project questions on one thread so folks can see what you're working on and what's been previously asked and answered. We can give it a more generic title any time you'd like.

[eagle0001]

Understood, CX. Thanks! Please rename my "Greenboard Ceiling" post to "Rolly's Bathroom Remod".

Thanks again!

[chefwong]

Rolly -

For all ceilings, even *moist* ones like bathrooms, I prefer 5/8" Firecode Sheetrock as it's much stiffer IMO than MR variants.

[eagle0001]

Thanks Alan. That's comforting to know because I have already tore down the greenboard and installed 5/8" sheetrock.

Thanks again!

[RaymondJ]

just for completeness, should anyone else happen upon this thread; a decent way i've found is that if you have 24" o.c. ceiling joists, and want 16 or 12 o.c. for mounting ceiling drywall; you can attach thin furring strips perpendicular to the joists at a 12 or 16 o.c. schedule;

if you have a nail gun, that tends to be much simpler and probably cheaper than adding additional joists; especially depending on whatever wiring, plumbing and mechanical situations there may be.