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

[Dp22]

I've been searching thru the archives for a while and I haven't found the answer to my question.

I forgot to apply thinset before using deck mud for the pre pitch. While I know it's something that I needed to do first, I don't know why?

The deck mud is a little sandy. It's strong in my opinion, no cracking. I have no problem removing and reapplying as there's a low spot near the top right corner that I need to fix with thinset anyways. (And a high spot that I've been trying to shave down a little near the curb.)

I also vacuumed around the drain and it picked up a 1.5" x .5" chuck right at the drain. I set the drain .5" above the floor to allow more compaction there. I had a tapered nozzle on the vacuum and it accidently touched the side.

I made new deck mud and just filled it. Maybe that's the wrong thing to do. I did the same for a small divot less than 1/4" off the surface.

My main question is, is it critical for the longevity of the pan that thinset is used before the pre pitch?

On a side note. I'm planning on building a monument shower bench. Also, I'm planning to attach the pvc liner to the studs in the front of the shower as my backer boards aren't 3" above the curb. I guess that's o.k..

Thank you all.

[Kman]

Welcome to the forum.

So here's the scoop on your unbonded mud bed. Yes, it's supposed to be bonded to the floor to keep it stable and in one piece.

Your low and high spots are better fixed while the mud is being placed before it dries. The high spots are easier scraped off then. And adding a little mud to a low spot doesn't always work.

Tell us how you plan to build and waterproof your monument bench, and I can tell you if your mud bed is worth saving.

[Davy]

Not sure which backer you plan to use but I would use a true cement board that allows you to embed it into your top mud bed. Hardie isn't supposed to be embedded in the deck mud. The fasteners need to be 3 inches above the curb height, not the bottom edge of the CBU. With the fasteners that high, embedding the cement board holds the bottom edge in place. You might also notch the studs so the folds in the liner won't cause the CBU to bulge out.

[cx]

Welcome, David.

I'm most curious about your curb. You appear to have a finished curb before you've installed your waterproof liner. What's the plan there?

Originally Posted by David

Also, I'm planning to attach the pvc liner to the studs in the front of the shower as my backer boards aren't 3" above the curb.

And I'm afraid I don't understand that part at all.

My opinion; worth price charged.

[Dp22]

Hey.
Thanks for the response. I was planning on building the shower using wonderboard, specifically wonderboard light in 7/16". I assume that's ok for the walls and to be immersed in the floor mud for the pre slope.

The monument bench I was going to build with mortar S with cinderblocks. Filled with mortar and a few pieces of rebar sloped to drain with a notch to go over the curb.

I used two bags of quikcrete deckmud for the shower with the first bag using the acrylic fortifier (I guess I didn't need it come to find out) . That mud happened to be where the bench will be and it's rock solid. No hollow sound. The second batch is definitely more hollow sounding. This was used around the drain which sounds hollow and a few other areas.

Yeah, so before looking back at this thread I made up my mind to bang it out and follow the proper procedure. Even if I don't quite understand it. I took the spiked end of the hammer and hit the bed about 4 inches from the drain in a hollow sounding area. It didn't crack but chipped off 1/4" off the surface. How in the world it didn't break into a zillon pieces is beyond me.

I have a quick question about floor mud. I bought 209 floor mud (deck mud) from floor decor. 1 dollar a bag as the bags were torn during delivery. Not ever wanting to pass up a good deal I bought them but I assume they are o.k. to use??

CX. I haven't put the liner in yet. The curb is only concrete. I made it 3.5" wide so I do need to build it up with mortar when I get there. Just trying to get there.

[cx]

Originally Posted by David

I assume that would be suitable for the walls and to be immersed in the floor mud for the pre slope.

Perhaps some confusion there, David. Your wallboards will never see your pre-slope. They can have their bottom edge embedded into the top mortar bed, though, the mortar bed that's on top of your waterproof liner.

Originally Posted by David

1 dollar a bag as the bags were torn during delivery.

Before I considered that a bargain, I'd wanna know the manufacturer date and how long those bags had been open, David.

My opinion; worth price charged.

[Dp22]

Great. Well after talking with laticrete I should just return em.

I do have a bag of quikrete deck mud that has been opened going on the 3rd day. It's been stored indoors around 75 degrees or so. That's safe to use or should I toss it?

Thanks for clarification on the preslope!

[cx]

A few days in conditioned space should not cause any harm to your bagged product, David.

I've never seen Quikrete "deck mud." What is the product number of that material?

My opinion; worth price charged.

[Davy]

David, after you wrap the liner over the curb, you'll want to wrap lath over it and then mud all 3 sides. You can't fasten the lath to the top or inside, just the outside. You'll want to over bend the lath so it will cling to the curb.

[Dp22]

Hi CX,

Here's the info.

https://www.quikrete.com/constructio...4-50%20-76.pdf

Got it from Home Depot..

Thanks.

[Davy]

I've never seen that in my area. I'd probably use it, or at least try it if it were here. Do you remember the price per bag?

[Dp22]

Davy,

About putting the liner over the curb. I was planning on using a decent construction adhesive to glue the pvc liner to the front side of the curb. I really didn't want to use Tapcons or anything. This is construction adhesive I was planning to use. It said it was good for concrete and pvc. Although I'm sure it's talking about pvc pipe.

https://www.loctiteproducts.com/en/p...ueezetube.html

On the oatey video on youtube they place a cut liner over the curb only and then one solid sheet of pvc over the entire pan and curb. I guess because it's a wood curb is the only thing I can think of.

On the plywood backing strip in the back corner where the bench will be I angled the plywood inside the corner stud 1/4" to leave room for the fold. I guess thinking I wanted to stud there for support. I'm thinking that should work but I should just get the liner out and see if I can pull that off. (I already cut the 1/4" notch up about a foot and then thought. I'll just push the plywood back thinking it was easier.)

I'm officially back to square 1!! Now it's round 2!

[cx]

I couldn't find a price from Homer's, Davy, and their site says the product "is not available within 100 miles" of my zip code.

Says on the bag, sorta, that it meets the right ANSI standard, but that particular standard says " Mix ratios can vary depending on local materials." No tellin' what might be in those bags, eh?

[Dp22]

The deck mud at HD says it's $7.98 a bag.

[Dp22]

Hmm. According to the quikrete rep. deckmud should not be used for the shower pan. He recommended either the sand/topping mix or the floor mud.

So, I won't be using the deckmud after all. Even though lots of people have used it for that.