Unbonded pre pitch... forgot to use thinset before applying deck mud to concrete slab

[cx]

Originally Posted by David

His recommendation was placing the cbu on or 1/8" above the pvc liner and redguarding the entire shower pan. Essentially sealing the wonderboard and pvc liner together without disturbing the weep holes.

Pray tell who's tech support recommended using RedGard over a PVC liner?!!

The use of mortar for the shower walls is certainly a good idea, but the CBU, properly done, will also work quite well. The hot-mop is just a local tradition out there and not necessarily better than a traditional PVC or CPE pan liner.

Apparently lots of California tile professionals have never made a tile shower receptor on their own and know no method other than hot-mop, which someone else does on their behalf. You can either accept their method or continue shopping for a contractor who will do what you want done.

My opinion; worth price charged.

[Snets]

Being here in CA, or at least Northern CA, I can tell you that hot-mopping seems to be dying. Everyone I talk with in the business here is using the major brand systems available today, or a traditional PVC liner method.

Going back to page 1 of this post, yes, Quikrete does sell their "Deck Mud" here in CA in the big box stores. It is sand and Portland Cement. I used it in my last shower and will be using it the next one. It worked perfectly. I don't remember if it is 4:1 or 5:1 but I do know it said the ratio on the bag. Either way, it worked well.

[Dp22]

John.
Technically, quikrete recommends either floor mud or sand topping mix. I know the data sheets for both have compression figures where the deckmud data sheet has no compression rating. Although it's mixed at a 5:1 ratio.

Just relaying what the rep said. I don't have enough experience with mortars to know.

David

[Dp22]

Hey CX,

I don't want to mention which company the rep worked for as given the permanent nature of posts on the Internet. If just rather not get into that.

It was the first time I heard of something hybrid like that. But the way I see it. It does if anything prevent water from migrating into the cbu and wicking up the liner. I know that's been seen and debated about before. I don't have the experience to have an opinion on it.

But in a strange way it does make sense to me to put regard or something similar on top of the top bed and seal everything to an inch perimeter of the drain. But it does inhibit evaporation under the sealed top bed if water does make it to the unsealed top bed 1" around the drain that should migrate to the weep holes.

The last time I was a part of a shower construction membrane products like regard didn't exist.
So?

[cx]

Without knowing what product manufacturer is recommending what product or application, there's no way to have discussion with them to determine just what they have in mind, David.

And you indicated you were told to paint the RedGard on the PVC liner, not on the top mortar bed. That's what I was questioning.

But painting a liquid waterproofing membrane on the top mortar bed is still a very bad idea in my opinion. There will be moisture getting into that mortar bed and there will be no way for it ever to evaporate out as it does in a traditional shower receptor construction. An opportunity to give your grandkids some of the very same water molecules that were around in grandpa's day.

If you want to use a liquid-applied waterproofing membrane for your receptor, and you think it will work long term, do that. But if you're not confident that it will waterproof your receptor, why would you paint it on there over an already fully waterproofed receptor? That's not overkill, that's just a potential for plain ol' kill, and I wish you'd eliminate it from your plan. Pick the waterproofing method with which you're most comfortable, install it per the manufacturer's instructions and tile industry standards, and never look back.

My opinion; worth price charged.

[Dp22]

Hey CX,

Thanks for the response. Well, it's interesting as there are so many product lines available to make showers now.

I called Durock yesterday and the tech rep said that using a silicone on the bottom edge of the CBU leaving the cbu about 1/2" above the liner would get rid of water migration.

I don't know if that's there official stance on it but it appears the manufacturers are addressing water migration into the cbu edge and wicking.

But, I will take your advice and pick an approved manufacturer method and go forward!

Thanks so much!

[cx]

I personally think putting a sealant on the bottom edge of the CBU in a traditional receptor construction is a bad idea, and I'm not sure why the Durock manufacturer would thing otherwise. With the silicone on the bottom edge, there will still be water wicking up the wallboard if there is water available. In a properly constructed shower receptor, however, there will be no standing water in that area. There will be water filtering down through the top mortar bed, and some of that may wick into the wallboard, silicone or no. But if the bottom edge is left open, said moisture will tend to gravity feet out the bottom of the wallboard. Some may wick up a little above the top mortar bed, quite harmlessly, and will evaporate in whatever direction is open.

Proper pre-slope under the waterproof liner, no standing water anywhere. No standing water, no significant wicking. Simple concept. Told to you by a guy you've never met, whose background you don't really know, who you found on an Internet site. See my warranty information below.

My opinion; worth price charged.

[Dp22]

I just wanted to give an update on the shower.

I applied a high grade modified thinset and 209 floor mud to correct the poor angle from my previous mistake. Once the thinset slurry and floor mud dried water would not flow thru to the weep holes. It would basically be standing water for 10 minutes where as deck mud was porous enough to drain to the liner nearly instantly.

The other thing I had a difficult with was trying to get it up. I have a hammer drill and getting it out was diffiicult in the areas that were modified with the thinset slurry and additional deck mud. My theory was use a pointed tip to break it up away from the edges and use a flat bit to slowly pry and wedge the deck mud out.

That worked great except when a huge chunk just collapsed and I the pointed tip hit the liner. I guess it punctured it there or in one or two other areas that happened.

Anyways. Just giving a follow up. The idea of fixing the bad top bed install with a modified thinset slurry wouldn't allow water to penetrate to the liner effectively in my case. It would have been easier to remove it when it happened as it would have broken loose quite easily. Just relaying information for others if they come across it.

But since the water test failed I don't know of anything else to do except take the liner out and go from there. I'll probably get it hot mopped I think and hire a pro. But, just wanted to follow up on the shower project.

Good luck with your shower installs.
David