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-   -   How thick should a pre-slope be over a Concrete foundation (https://www.johnbridge.com/vbulletin/showthread.php?t=127843)

Lucy_Dawg 07-23-2019 08:41 PM

How thick to make a shower pan
2 Attachment(s)
I was hit last fall by hurricane Michael. I have been rebuilding my house for months and am to the shower now. We had to remove the old shower, which had a rather large molded corian shower pan. I couldnt get it out, so I finally got the crow bar and pryed it out, snapping the 2" PVC drain pipe. I am needing to repair that first, then make the floor have a 1/4" p/ft drop down to drain. How thick should this pre-slope be? Can it be like 1/8 of an inch at the thinnest point, or should thick should it be exactly at the thinnest spot (Drain)?

Next I will have to water proof it, and was planning on using rubber sheets, folded and stapled to wall. I have since seen some paint on stuff (Redguard) as well as some orange sheet material, that is taped at seams. Since this is my first time, should I venture to something like that, or stick with the rubber sheets folded method?

Once the waterproofing is in, how thick should the shower pan be at the thinnest section?

I need to know this, so I know how high to set my drain, which should be set before I can pour the pre-slope or shower pan, correct?

To make things more difficult, my shower has a built in seat, so I will have to waterproof up, then turn back horizontal, then up wall some more, to waterproof in seat.

As for the pre-slope and pan, is there a specific mortar mix I should use, or stay away from? I see some mortar that costs around $8 for 50 lbs, then others that is $20 for 10 lbs. Why the huge difference, is there something Im missing right here?

Thanks in advance, it is greatly apprecaited!!!

cx 07-23-2019 09:59 PM

Welcome, Paul. :)

You've gotta decide first what kind of water containment system you want to use before you can even decide what kind of drain you want to install.

You can build a traditional receptor with a mud pre-slope, then a PVC or CPE liner (not rubber), for which you'd want a standard three piece clamping drain. But if you intend to keep that wood-framed bench, I'd recommend against that.

You could use a direct bonded waterproofing membrane system. The orange one you mentioned is sold by Schluter Systems and is called the Kerdi Shower System. My preference is for a gray one sold by USG and is called the Durock Shower System. With the Kerdi system you can use gypsum drywall as your backing material if done per the manufacturer's instructions, but with the Durock system you need to use CBU.

With either of those systems you need to use a bonding flange drain that is part of the system and you make a single mud floor, properly sloped to the drain. Over that you apply more of the same waterproofing membrane. You'll need to do a little research on both, but we've helped many hundreds of visitors build such showers.

The deck mud you want for the sloped floor of any type receptor you build will be a very simple mix of sand and Portland cement mixed in a ratio of five to one with a little water added. You can find much information on that in the Shower Construction section of our Liberry.

Decide what type of shower waterproofing you want to use and we can deal with your specific questions at that point.

My opinion; worth price charged.

jadnashua 07-24-2019 08:31 AM

My preference would be to use one of the sheet applied waterproofing methods. When done properly, the entire shower, from the pan all the way up the walls, is waterproof. In a conventional shower, the waterproof liner on the pan only goes up a few inches above the curb height...the rest is typically water resistant. Now, gravity plays a big part in that...the water always will end up down on the floor and the small amount that gets into the walls tends to evaporate. There should be a moisture barrier behind it to protect the studs, but it is not technically waterproofing.

The sheet applied waterproofing is sort of like putting up wallpaper except you're using thinset as the glue. There's more to it, but it's not usually as daunting as you might expect.

Lucy_Dawg 07-26-2019 04:20 PM

I had to bustout my old drain, and now have a hole in the middle of foundation. I am about to replumb it, but first have to determine how thick I want the pre-slope at the drain? This should be the thinnest spot of concrete (Sand/Portland Cement) mixed at a 4:1. Is there a specific thickness I am looking for in my pre-slope?

Lucy_Dawg 07-26-2019 04:31 PM

How thick should a pre-slope be over a Concrete foundation
I am about to make a pan on my first shower, and have a concrete foundation, and the drain was busted out. So I chipped away some concrete foundation to get to drain pipe. I need to know how high to plumb the drain. Specifically, how high do I want my pre-slope to be (How thick) where the pre-slope meets the drain?

1.5 - inch?

thanks in advance

cx 07-26-2019 05:15 PM

Paul, please don't start new threads with the same questions as it results in confusion and duplication of effort on the part of our all-volunteer army of helpers. If you don't feel your getting a timely response, make another post to bump your thread to the top of the queue for attention.

There is no requirement for any part of an actual pre-slope in the ceramic tile industry because the pre-slope in a traditionally built shower receptor is part of the plumbing and their requirements don't address your thickness question. That's why I asked what type of receptor you're planning to build.

My personal minimum for any deck mud application, regardless the type of drain or the type of waterproofing, is 3/4ths of an inch and that might well apply to your application. But that doesn't really tell you how high to plumb the drain as we don't really know what type of drain you intend to use, eh?

My opinion; worth price charged.

Lucy_Dawg 07-26-2019 06:25 PM

Good point. Here is my plan....

- Fix the busted drain pipe, plumb in a new drain.
- Fill the busted conceret hole with a mixture of 4:1 Sand mix:Portland Cement. - Then use that mix to fill the hole as well as make a pre-slope.
- I will then use pvc mat, to make a pan liner, that will drain to a 3 peice drain.
- I will cement board the walls, fill joints with non modified mortar and some 6" fiberglass mat.
- Then I will redgard along the corners and edges, apply a waterproof tape into wet redgard, then smooth with troxel. Then do 2 complete coats of Redgard from the ceiling to the shower pan.
- Pour a shower pan, with 1/4" drop per foot for both shower pan and pre-slope.

Is this the right way to do this?

Thanks again!

Davy 07-26-2019 06:57 PM

I'd set the bottom flange part of the drain 1/2 to 3/4 inch off the slab surface. Use concrete mix to fill in just to the top of the slab. I also like to paint on thinset to the edge of the slab to help the concrete bond. Rebar can also be drilled into the edges of the slab if you want to.

Then use a thinset slurry on the concrete to bond the dry pack preslope up to the bottom flange. I'd go 5 to 1 with the dry pack.

I'd also notch the studs so the pan liner will set back a little from the face of the studs.

cx 07-26-2019 08:00 PM

4. For finishing the CBU you want to use a 2" alkali resistant fiberglass mesh tape. You can use an un-modified thinset mortar to fill the joints, but there is no reason not to use a modified mortar if that's what you'll have on hand to set your tiles.

5. Not sure what you might mean by "waterproof tape" there, but Custom makes a fiberglass mesh they recommend for use with RedGard in that application and that's what I'd recommend you use.

6. By the time you get to installing the wallboard you should already have installed your pre-slope of a minimum of 1/4" per foot from the drain to the farthest corner of the shower. The final mud bed over that liner should be of a consistent thickness of a minimum of 1 1/2 inches, following the slope of your waterproof liner and capturing the bottom of your CBU wallboard.

My opinion; worth price charged.

Lucy_Dawg 07-26-2019 10:26 PM

how you suggest I do the bench, if I dont concrete board the top and footboard. I plan to add a slight pitch to the top.

Kman 07-26-2019 10:50 PM

With that kind of water containment system, you could build a bench with block and mortar inside the liner. No need to waterproof it, which is an advantage.

You could also install a Better Bench, just add some blocking before installing cement board to secure the bench. You would cover it with Redgard at the same time as your walls, but since it's filled with deck mud, you'll have to wait three days to waterproof it. If you're not pressed for time, it's a good option, since it doesn't take up any floor space.

Davy 07-27-2019 02:15 AM

What Kevin said, I add more pan liner on the studs in the area that's behind the seat and along the sides draping it over the floor pan liner that goes up the walls. Then build the seat inside that using concrete blocks and mud. It works well and is probably the cheapest way to build a seat.

I wouldn't have a problem using the Better Bench, it also makes a very good seat.

Lucy_Dawg 07-27-2019 06:54 PM

1/4" rise on pre-slope on top of foundation
1 Attachment(s)
I understand that you need to have a pre-slope with 1/4" rise per ft, then put the shower pan on top. lets say you are building a square shower, and the drain is in middle, there should be even height across the corners, what happens when you have an oblong shower, and the drain is offset? How do you maintain the correct slope, and also a level height around the edges? Should I just lay the pre-slope according to the 1/4" rule, then when I do the Shower pan, I make sure the edges are level then?

In my picture above, to top right corner, is 48" so it should be 1" above the drain. From drain to the bottom side of shower, is only 16", so it should be like 5/16 above shower drain. There is no way to keep the heights level. Im thinking make level when I install shower pan, but dont want to do it until I am positive.

Thanks for the help!

cx 07-27-2019 08:14 PM

Paul, please keep all your project questions on one thread so folks can see what you're working on and what's been previously asked and answered. A moderator can give it a more generic title any time you'd like to suggest one.

See Post #9.

The required slope is a minimum requirement. You would make your perimeter of the pre-slope (again we're assuming you intend to build a traditional shower receptor) level all the way around at the level of the maximum height. In your case that would be a minimum of 1" higher than the top of the bottom portion of your clamping drain. A bit higher is better to be sure you meet the minimum requirement. The slope will be different in the other quadrants of your receptor because of the drain location.

I would recommend as your first step that you center the drain in the shower footprint.

My opinion; worth price charged.

Lucy_Dawg 07-28-2019 12:04 AM

Thank CX. I will keep all post regarding my shower in this thread. Sorry about that. Thanks for the replies. I am going to get rolling on this tomorrow. Since my drain is 3/8" above foundation, I will just go to top of floor plate, approx 1.5". That will make it easy for me to drag the sand mix anyways.

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