Pre-Slope, Slope, Drains, Membranes....I'm confused.

itltrotFebruary 21, 2014

The plumbing has been moved finally. Now we are close to starting the shower pan. I think I get a handle on it and then I get confused. So here I am confused. We are pretty capable DIY'ers but this is our first tiled shower pan.

We have a concrete slab. We recently rerouted plumbing and patched the floor where the shower is going. There is also a settling crack that has shown up in the new to be shower floor.

What do we need to do with the patch/crack before starting the pan?

I think I've got a handle on the pre-slope (I'll probably cheat and used the quick pitch products).

Then goes the membrane. I don't know what to go with at this point. Standard shower pan liner like oately or do I try the (scary to me) Laticrete or Kerdi products. My shower is an oddball size so I can't buy the preformed pans. At least I don't think I can. Shower size is roughly 36" x 66".

Then the shower curb. Do I just use the quick pitch curb or do I go with something from Laticrete or Kerdi?

Then the slope. Again, I'll probably cheat with the quick pitch slope products.

Now the drain. I give up on understanding when it comes to the drain. The divit method or flanged drains just make my overtired brain spin. All I know is I need one but beyond that I'm stuck.

Thinset and tile, no problem. We've done that a few times. The rest is all new and overwhelming me. I just want to do it right so I don't have to post on here in a couple months that my shower's not draining.

I appreciate any guidance I get.


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If you do the Hydro Ban paint on coating on top of the shower pan, then you do not need a preslope and a liner. The moisture barrier is the Hydro Ban. You can use a Laticrete Hydro Ban Bonding Flange shower drain or a Kerdi shower drain. I think the Hydro Ban drain is cheaper. Both Hydro Ban and the drains are cheaper online. Lowes carries Aqua Defense and Home Depot carries Red Guard. All three of these coatings can be used on shower floors and walls.

You can buy a Kerdi or Hydro Ban foam curb. Or you can use bricks and mortar with thinset on top. Or kiln dried 2x4 (not trested) covered in cbu. Your choice. Materials, skill level, finished height, shape, etc.

Check out videos on youtube. Andof course search this forum.

For your settling crack in the shower pan, I would create a separate thread paging Mongoct for his advice, He's the hyper expert. I would post a picture too.

This post was edited by Anna_in_TX on Sat, Feb 22, 14 at 4:28

    Bookmark   February 21, 2014 at 2:25PM
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It sounds like you have a lot more reading to do. Check out the john bridge forum, they have a lot of good info. You are confusing (at least) three different systems. The traditional way uses a preslope, vinyl liner, and second layer of mud on top of that (which follows the same slope as the preslope). You use a clamping drain with this system. Kerdi is a topical membrane. You have to use a Kerdi drain with this. The Kerdi is applied to a sloped mud bed (no preslope - there is only one layer of mud, so no pre). Laticrete now makes a drain similar to the Kerdi drain, so you can use Hydroban with their drain, and not have to deal with the divot method. Don't use the quick pitch things. They're a gimmick, and in my opinion will compromise the integrity of your pan. And definitely DO NOT make your curb out of lumber, since it's on a concrete slab. The lumber will constantly wick up moisture from the slab, causing it to swell and leading to eventual failure.

    Bookmark   February 22, 2014 at 12:42AM
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Thanks. I knew I was confused and I'd looked at tons of posts here and some at John Bridge but seemed to only be getting more confused with each one.

Is Kerdi really DIY friendly? I've seen a few posts here and there where DIY'ers have had problems with install.

Any idea how much the material for my shower would cost kerdi vs traditional? I don't have any place local to buy kerdi so I'd have to order it online. Any suggestions on where to buy? Oh the joys of small towns.

Again, I appreciate the help.

    Bookmark   February 24, 2014 at 12:13PM
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To simplify:

There are 2 mud shower floor construction methods:
1) preslope + pvc liner + top mud bed + thinset + tile.
Use a clamplng drain with this method.

2) sloped mud bed and ( (thinset with Kerdi or Pro Source plastic fabric) or (Hydro Ban or Aqua Defense or Redguard liquid membrane) ) + thinset + tile.
Folks like to use a Kerdi, Hydro Ban, or Pro Source drain because they have wide flanges for the moisture barrier to adhere to.

Most newbies prefer the paint on liquid moisture barriers. The Kerdi or Pro Source fabric is installed with thinset like wallpaper. These moisture barriers are applied over the curb.

Most newbies like to do cbu walls with the moisture barrier on top, especially the paint on liquids. A plastic moisture barrier behind the cbu can be done, but is not the best way.

The reason why the topical moisture barriers are superior is that the cbu in the walls and the mud bed in the floor never get wet. Thus, the showers dry out more quickly.

Hope that helps.

This post was edited by Anna_in_TX on Mon, Feb 24, 14 at 19:41

    Bookmark   February 24, 2014 at 6:29PM
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I'd like to go with Kerdi but like I said I can't find it locally and I'm not sure where to shop for it. I've looked a couple places online but I'm only finding the full kits with the sloped foam pan.

Thanks for the help, I guess I'll try making another post to get some input on the crack.

    Bookmark   February 26, 2014 at 1:16PM
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If you want to do a standard mud bed preslope with an Oatey membrane and a 2-part clamping drain, read this for a bit of guidance.

If you want to read some basic guidance on how to do a Kerdi shower over a mud bed, check out this thread. FWIW, that was my first time using Kerdi.

If you want to use Hydroban and a Laticrete flanged drain, the prep work is the same as the Kerdi thread with regards to cement board on the walls and a sloped mud bed on the floor. But instead of thinsetting Kerdi, you simply paint on the Hydroban.

Don't bother with Hydroban and the Divot Method.

Online sources for Kerdi?

Tile Protection

I'd venture that overall, the easiest would probably be Hydroban with a Laticrete flanged drain.

As to the mud bed, they can be a bit of work, but they certainly are in the realm of DIY. If you really wanted to use a manufactures tray like a Schluter/Kerdi tray, you could buy the 30" by 60" tray:

Cement board the walls. Then center the 30" by 60" tray in your 36" by 66" space and thinset it in place. Then fill in the 3" wide gap around the around the perimeter with deck mud.

Don't fill one side to the top and pack it down all at once, you could dislodge the tray. Instead fill in an inch of mud around the whole thing, then pack it all around. Then fill to the top and pack it again.

Match the slope of the tray surface across the top of the deck mud, so the slope is continuous from drain to wall.

    Bookmark   February 26, 2014 at 4:51PM
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Mongo- Thanks for the information. The links will be very helpful in making our decision. Especially now that I know where to buy it!

Here is a picture of the slab crack and the plumbing patch. Do you have any advice on how to tackle this and prevent it from being a problem down the road?

Thanks again!

    Bookmark   February 26, 2014 at 5:45PM
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Much depends on the reason for the crack, and if the crack is active or if it's old and has stabilized. ie, no more movement.

If the crack is active, it's an "all bets off" type of scenario. There's no sense in tiling over an actively moving slab. I'd need to know why it's moving. Expansive clay underneath? Water issues? Poorly compacted subsoil that has settled and thus the slab has sunken in? There are myriad reasons.

Not all cracks are problematic. Large expanses of concrete can show shrinkage cracks. They are simply a part of the curing process. Shrinkage cracks will never move, they really aren't an issue.

Some structural cracks are done. They've moved. They've settled. They've stabilized. They'll never move again. So not all structural cracks are an issue. It's simply actively moving cracks that you need to be wary of.

SInce you've already made patch repairs to the slab, I'm guessing that the existing cracks are not active. Were they active I'd have recommended digging out the broken concrete. excavating down, filling and compacting a new base, then repouring a new slab.

For your case with the cracks being inactive, I would put a crack isolation membrane down. That'll serve two purposes:

1) It'll isolate the cracked slab from your mud bed.
2) It can act as a moisture barrier, preventing moisture in the earth below the slab from wicking up through the slab and into your new mud bed.

A crack isolation membrane I use is Nobel CIS.

You can then put your mud base on top of the CI membrane and work up from there. I'd recommend Hydroban with that. Hydroban is a water proof barrier but not a vapor barrier, so it'll work well with the CIS which is a waterproof and vaporproof barrier.

The good news? Sort of? If you use Nobel CIS (or use an equivalent product) over the entire bathroom floor slab, then you can put the sloped mud (or preformed shower tray) over the shower portion of the floor and then simply tile over the CIS on the remainder of the floor.

Do understand it's not the only way. There are other products you can use.

Does that make sense?

    Bookmark   February 26, 2014 at 6:43PM
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Honestly I have no idea if it's active or not. It's been uncovered for about 6 months and it hasn't changed in that time. It's not raised more on one side or the other.

DH thinks it's a result of the concrete being thin there and it being inline with the old wall that had plumbing which consisted of a 3" vent pipe and a water manifold. The concrete was maybe 4" and that's probably being generous. The wire they used was in the very bottom 1" of the concrete. Elsewhere were we moved plumbing the floor was closer to 6" thick.

We are in sandy soil and we have some evidence of settling in various areas but nothing that's real recent. Most everything (crack in brick above a doorway, crack in sheetrock in a doorway, crack above arched window in brick) have been there for years.

So you suggest the Noble on the whole bathroom floor. We plan to do heated floors in the bathroom. Do the elements go on top of the CI membrane?

Is Hyrdoban similar to Redgard? Or am I confusing products again? We used redgard in DH's shop bathroom. Really nasty to apply but wasn't to complicated.

Thanks again for the advice!

    Bookmark   February 27, 2014 at 9:45AM
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Heated floors changes things.

What you don't want to do is send heat down to earth. Earth is a big heat sink. I recommend adding a thermal break over the slab. You can use cork, or there's a synthetic cork that's called Cerazorb.

I recommend Cerazorb over the slab. CZ is simply a thermal break. There may be a bit of crack isolation built in to it, but it's not officially rated as being anything other than a thermal break. Being a thermal break, what it will do is reduce the amount of time that the RFH is running.

On top of the cork/cerazorb you can place your RFH. You can thinset it down and skim coat it with thinset to cover the wires, but attaching the RFH wires to the CZ and then embedding it in SLC is usually faster, less frustrating, and the SLC will give you a nice self-leveling flat surface to tile upon.

I still recommend the Nobel CIS on top of the SLC. It is a true anti-fracture membrane and it'll isolate the thermal stresses of the cycling RFH that occur below the CIS from the thinset-to-tile bond above the CIS.

Hydroban is indeed very similar to RedGard, they are both liquid membranes.

    Bookmark   February 27, 2014 at 11:01AM
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Mongo- Thank you for all the information. I'm studying it and researching where to purchase. DH and I had never seen mention of a thermal break on the concrete for the RFH but it makes sense to both of us and will proceed like you've suggested.

Just to make sure I understand completely.

Bathroom floor > Cerazorb > RFH > thinset or SLC (self leveling compound?) > Noble CIS > thinset > tile

How much height is all of this going to add to my floors just out of curiosity? Also the cabinetry isn't in yet and I planned on doing the floors at the very end is this still acceptable? I'm not 100 % of the cabinetry layout yet and know the RFH can not be installed under cabinets so I was planning on waiting until it was installed and then tiling the floors. But that was before I learned of the extras.

Shower floor > Noble CIS > mud bed > Hyrdoban > thinset > tile.

Should the Noble be one continous piece from the shower pan to the bathroom floor? Would the curb go on top of the Noble?

Thanks again!

    Bookmark   March 5, 2014 at 9:45AM
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Quick post:

Thicknesses over the slab? The following are not perfect, but estimations.

Cork = 1/4"

RFH mat generally 1/8" thick

SLC, which will encase the mat? The thickness depends on how much the slab is out of level. If the slab is dead level and you're simply looking for RFH wire coverage, the SLC can be about 1/4" thick, but generally plan on 1/2" thick. Could be more, could be less. The SLC will envelope the mat, so you can disregard the mat thickness as it'll be a part of the SLC thickness.

Noble CIS = 1/8" thick.

Thinset + tile = 1/4" thick

So Cork (1/4") plus SLC (1/4" to 1/2") plus CIS (1/8") plus tile (1/4") = 7/8" to 1-1/8" total thickness above slab.

If you want to add in a couple of layers of thinset (thinset to bond cork to slab, thinset to bond the CIS to the SLC, etc) you can add in another 1/4" for grins. So you could be looking at 1-1/8" to 1-3/8" thickness above the slab. But taking the middle road you'd probably be in the 1" to 1-1/4" range.

Shower floor, yes, CIS, then either your manufactured shower tray or your sloped mud bed, then Hydroban, then thinset and tile.

The Nobel can be seamed if the floor is wider than the Nobel.

Yes, I'd want CIS between the curb and the slab.

    Bookmark   March 5, 2014 at 11:06AM
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