Happy Dad's Shower Project

[1HappyDad]

An unexpected shower repair came up and it was necessary to have the shower stripped down to the studs, make the plumbing repair and now rebuild.

Getting a bit of conflicting information..now after the fact.

East wall faces a laundry room
South wall is a block exterior wall with 3/4" insulation board and 1-by's on top of that.
West wall is a 1/2 wall with treated 2x4's.

The plan is to use 1/2" densshield 4x8 sheets as the tile backer. It has not been installed yet.

3 coats of redgard was applied to the inside of the entire 1/2 wall -- studs and back of the purpleboard. Purpleboard is outside of the shower on the opposite side of the wall.

On the south wall, 1 coat of Regard was also applied to the insulation board face and 1-by's about 6' up the wall from the shower pan.

There is no plastic/vapor barrier between the 3/4" insulation board and the block wall. It is constructed as follows: Block, insulation board, 1-by's.

I cannot seem to find a straight answer if it was ok to apply redgard to the insulation board and 1-by's, then cover with denshield. There will be approximately 1" space between the denshield and insulation board that has the redgard coating.

The 1/2 wall I don't think is going to be an issue but as mentioned, the studs in that are covered with RG as well. This wall would receive a constant spray of water when showering.

The question is:

-- Is it ok for the face of the insulation board and 1-by's to have a coat of redgard applied as well as the interior of the 1/2 wall coated with redgard? Again, DensShield will be used for the tile backer.
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1HappyDad

[1HappyDad]

Pics

[Bdobz]

I'm no pro, but I don't understand why you applied redgard to the bare framing. Since you mentioned you are using Denshield, which is advertised to not need a sperate moisture barrier especially.
I am in the process of doing a bath surround using Denshield. I just applied two good coats of Redgard to the taped and thinsetted Seams, corners and all screw locations. Denshield says drive your fasteners flush with the board, but I had a good number countersink a little.
With the good amount of airspace you will have between the inseide walls and the denshield, I do not think you will have any issue with m=Vapor lock in there with two layers of moisyure barrier, but like I said I am a novice and just my thoughts.

Brian

[e3]

I’m not sure why you did it either but from the looks of it it’s not anywhere near thick enough. It is supposed to be about as thick as a credit card. I personally wouldn’t do it any water vapor that gets trapped in the wall has no escape, and the uncoated side of the Denshield is exposed to it.

[Carbidetooth]

The question is:

-- Is it ok for the face of the insulation board and 1-by's to have a coat of redgard applied as well as the interior of the 1/2 wall coated with redgard? Again, DensShield will be used for the tile backer.

Is it OK? Well, it's not against the law.

My thoughts:

1. Why? Moisture in any of these areas would mean something in the waterproofing scheme has been overlooked or misguided or simply done wrong.

2. If RedGard were meant to waterproof all manner of substrates, you'd think Custom would be quick to point it out in their product info...they don't. It's on substrate they don't consider suitable, but evidently someone does. I'll put my faith in the manufacturers guidance rather than the mish-mash I see in photos.

3. Denshield, a gypsum product, has to have its instructions followed to the letter in order to achieve "waterproofness". Rarely have I seen that done, and more importantly, I've seen failures when they weren't. I have no love for the stuff and in view of the alternative products available would not saddle a client with it and its inherent liability.

4. I would be interested to hear the theory behind applying all that RedGard and how it fits into the overall waterproofing strategy.

[1HappyDad]

The main concern is if this will create a “moisture sandwich”

But..if there is no moisture intrusion, it should be fine.

Denshield washighly recommended by most every contractor locally and came with a seal of approval from several inspectors that I know as well.

It will be a pain in the butt, but the half wall can be removed and reconstructed in about 3-4 hours, the insulation board will take about the same.

I simply cannot afford a moisture problem, if by removing and replacing the redgard covered items will save an issue in the future, I will do as necessary

[cx]

Welcome, James.

The problem with moisture is that it will always get into any space in residential construction, whether in liquid or vapor form, and you always want a way for it to escape. The very thin coat you've got on those surfaces will stop most liquid moisture, but not all the vapor migration. Custom has claimed it is, when properly applied, a vapor barrier, but I have asked several times over the years for them to provide me the test results showing that and have still never seen it. I know of no other liquid-applied direct bonded waterproofing membrane (ANSI A118.10) manufacturer that makes that claim.

That thin coating of RedGard will, however, be an impediment to moisture vapor escaping from the wall cavity behind your shower walls. If your wall is at all open at the top, or otherwise vented, that will certainly help.

If you would put a geographic location in your User Profile it will help in determining just how much an issue you might be creating. Knowing what's on the outside of that wall might help, too. But whatever the case, I would not rebuild anything because of the RedGard. I would, however, suggest you not do any more such "waterproofing" and that you defeat the RedGard coating wherever feasible.

My opinion; worth price charged.

[1HappyDad]

Thank you all for your replies.


I am in central Florida.

I will try to figure out the location setting on my profile, I apologize.

The wall that has the insulation board is an exterior block wall
Ie: open cell block to 3/4” Insulation board and then the 1-bys for denshield mounting.

The half wall is simply anchored to the slab with HTT braces and 5/8 sleeve anchors. Shower side and the top will be denshield, the other side is purple board.

This entire project started from a pipe leaking in the shower that caused a bit of mold, so I’m trying to be extremely careful when it comes to any moisture issues.

[jadnashua]

While liquid applied waterproofings can and do work when installed exactly as specified, my preference is a sheet membrane. On a sheet, your concern is the seams, and those, if you mix your thinset properly and follow instructions, are pretty reliable. Then, the entire shower enclosure is waterproof versus just the pan, and immediately beneath the tile all over. When doing that, your pan becomes simpler since you don't need two separate layers of deck mud (preslope, liner, then setting bed)...with those sheets, you tile directly to them.

It takes some practice to get something like RedGard the proper thickness with no pinholes or runs.

For anyone installing a liquid, get a wet film thickness gauge and learn how to use it properly. You'll probably have to adjust your technique and check frequently to get the wet coat between min/max.

[cx]

The vapor drive from the shower against that outside wall in your part of the country will likely be lower than the drive against the interior walls that probably have artificial cooling outside the shower for most of the year. Actually, when that shower is not in use the vapor drive on the outside wall is probably from the outside in. What will happen to the vapor that condenses in those cavities during the time the dew point occurs within the cavity? I dunno. In your part of the country you can probably expect the wood to rot eventually anyway, or be eaten by termites, eh?

DensShield, while a useful product in some applications, is just too technically complicated to use properly as the water containment medium in a shower application. Much more complicated than using CBU with either a moisture barrier behind or a direct bonded waterproofing membrane on the inside face. And remember that DensShield is not waterproof. I believe the manufacturer says it has a moisture barrier, but it's still a gypsum-based product.

As for the "purple board" in the rest of the bathroom, unless your local code compliance inspector requires some form of MR board there, I would much prefer to have plain ol' gypsum drywall in there. With a properly sized and used exhaust fan that room should suffer no more from moisture than does your bedroom.

My opinion; worth price charged.

[1HappyDad]

I suppose to be extra safe I’ll just demo the wall
And rebuild it. Same with the insulation board that is coated.

[cx]

I expect that insulation board already has its own moisture barrier on it, James. Not much use replacing that, I wouldn't think.

[Tool Guy - Kg]

Do as you feel for rebuilding the stud wall.

But I don’t think you’ve significantly lowered the perm rating of your foam insulation wall that already has a low perm rating and therefore wouldn’t rebuild it. I’d leave that as is.



EDIT: CX done beat me to it, I see.

[cx]

Aww, but it's comforting for us newbies to have some validation sometimes, Goldstein.

[1HappyDad]

Well, when I anchored the 1/2 wall down, I did quite a good job. It’s not going anywhere. I won’t be able to get it out without screwing up the anchors and possibly the slab. Not worth the hassle to re drill and try to anchor a new wall in.

So, as an alternative, I simply removed the purple board on the opposite side and used a rubber wheel to quickly strip the redgard from the studs. I didn’t have any solvent in the garage, but I had plenty of the eraser wheels as I do some auto work on the side / detailing.

ABN Rubber Eraser Wheel 4in Pad & Adapter 1-Pack – Pinstripe, Adhesive Remover, Vinyl Decal, Graphics Removal Tool https://www.amazon.com/dp/B018WG2XYE..._kzLNFbXYKZY52


I’m
About 1/2 way through. Hopefully I’ll have the purple board back up tomorrow.

The general agreement seems that I could leave the insulation board and 1-bys alone as they are...I think there is 1 heavy coat painted in the 1 bys and 1 light coat on the insulation board