all 19 comments

[–]Potusmicropenis 2 points3 points  (9 children)

Are you sure you want to use MR drywall and not wonderboard or an equivalent?

[–]Few_Scratch_3261[S] 0 points1 point  (8 children)

Are you sure you want to use MR drywall and not wonderboard or an equivalent?

Hmm, I confess I am ignorant on the subject. Please share what you know - is the MR drywall an inferior product as compared to MR drywall? Does it offer better waterproofing protection?

[–]Potusmicropenis 1 point2 points  (4 children)

So. MR sheetrock is just that. Moisture resistant not waterproof. Durock or wonderboard cement board are waterproof. 5/8 is the thickness to use. And redguard is a good idea. I hate to tell you this but you should demo that sheetrock and install cement board and red guard the whole tub area. Otherwise you’ll be doing it in a few years at best.

[–]Fixturefanatic 0 points1 point  (3 children)

I missed your comment while I was writing my own, but I disagree. The MR drywall is just fine with redguard and it will probably never have issues. The only upgrade I can think of is using Kerdi membrane instead of the redguard, but for a vertical surface I think it will be just fine. I wouldn't lose sleep over it, especially if it is not the primary shower.

[–]Potusmicropenis 0 points1 point  (2 children)

You’re already into it. Why not use wonderboard and sleep like a baby? A big happy baby!

[–]Few_Scratch_3261[S] 0 points1 point  (1 child)

Use wonderboard how? As an alternate to the green board? Thanks for your reply!

[–]Few_Scratch_3261[S] 0 points1 point  (2 children)

I have started reading up on some of the differences between the cement board and green board here:

[–]Fixturefanatic 0 points1 point  (8 children)

Looks good to me. Nothing wrong with the MR drywall if it's properly waterproofed, although I would have used Kerdi membrane over it since you plan to shower as well. That pink stuff looks like Redguard or an equivalent, and although I don't trust it I know a lot of contractors do. As it is, it is still much better than a lot of old shower/tub jobs that have lasted a long time.

[–]Few_Scratch_3261[S] 0 points1 point  (7 children)

Kerdi membrane over it

Thanks for the reply. So your recommendation is to put Kerdi membrane over the green board?

[–]Fixturefanatic 1 point2 points  (6 children)

After reading up a bit on Redgard, I agree that situation is not ideal. The Redgard product description lists drywall as a suitable substrate, but only for "interior dry areas". However, the walls of the tub serve to protect the low section of the shower, which is the most susceptible to problems. If left unnoticed I doubt there would be an issue with this install, but of course we're trying to get you the best results.

If you want to do it right and still use Redgard, then yes the righteous thing to do would likely be replacing the drywall with a cement type backerboard as u/Potusmicropenis suggests

However, a membrane such as Kerdi (not a rep, just a fan) is meant to be used over drywall and could likely be installed over the existing drywall/redgard. I would probably chose to do that if I was taking over the project.

After working with it several times, I have more faith in drywall & kerdi than Redgard & cement board.

Edit: I found this video on youtube regarding Redgard, it would certainly help me sleep if I had any concerns. But I would definitely make sure multiple coats were applied.


[–]Few_Scratch_3261[S] 0 points1 point  (5 children)

Very insightful analysis u/Fixturefanatic very grateful to you. I need to speak to my contractors ASAP, but before I do, could you please link me to the type of Kerdi that would work in this application? The Kerdi membrane I have seen typically is for an underlayment flooring. Schluter makes a Kerdi prodcut but I cannot be certain if this is the proper one to get...

[–]Fixturefanatic 0 points1 point  (3 children)

Okay, so I hate to go back on something I said, but it would bug me if I didn't mention it.

I looked into it a bit, and there could be complications with installing the Kerdi membrane over drywall that's had Redgard applied to it. You'd be layering two waterproofing materials and that is also not ideal. Kerdi recommends that their membrane be installed on new drywall that hasn't been taped (their membrane acts like tape in that it covers the whole surface, bridging the joints with ease). Also, the surface is now probably somewhat uneven from the tape job and the redgard, and after they add another layer in the form of Kerdi that could lead to problems when it comes to tile setting.

As I see it there are three options:

1) Stick with the Redgard over drywall (not recommended but probably won't have any issues IRL)

2) Do as u/Potusmicropenis suggests and have them swap the drywall with cement board, then use Redgard

3) Replace the drywall and only apply Kerdi membrane over it

I would do step 3 if I could start from the beginning, but you may be just fine with option 1, especially since you have the tub protecting the lower portion of the walls. I guess it depends on your relationship with the contractor.

I'm sorry to muddle this post up, please forgive me! Hopefully someone with more experience can weigh in.

[–]Few_Scratch_3261[S] 0 points1 point  (2 children)

I spoke to my GC about this situation and she told me that cement board it is old school because before they didn't have this material, and green drywall is much lighter and more durable also but just in case we put on top water proof coat of redguard.

I think I disagree with some points in what she says based on what I have learned here. Is Kerdi superior to Redgard in your opinion?

[–]Fixturefanatic 1 point2 points  (1 child)

In a shower setting, green drywall needs additional protection, so the coating of Redgard is not "just in case", I would consider it a minimum. Although many showers have been done that way.

I think your installer is probably trying to right by you, and what they've done so far will probably work. *But\* since you are asking for the work to be critiqued I would say it doesn't offer the same level of protection as a sheet membrane such as Kerdi.

Here is a link to another forum where they describe a similar situation to yours. There are many such threads if you do a google search for the use of Redgard over drywall in showers.


[–]Few_Scratch_3261[S] 0 points1 point  (0 children)

Thank you u/Fixturefanatic for your links and your replies. I have more to learn obviously.

[–]chopsuwepro commenter[M] 0 points1 point  (0 children)

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