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dave.adams 05-26-2017 07:00 PM

Shower Remodel
1 Attachment(s)
I'm in the middle of a complete bathroom remodel, demo'd everything down to the studs.

At this point the drywall, floors, vanity, and toilet are in, and I'm about to start on the shower.

I'm a bit paranoid about building the shower pan as I seem to have stumbled across all kinds of horrible YouTube videos of tile guys ripping out bad shower jobs. So I'm looking for some advice to make sure I get it right as this is my first time:

(1) the drain is flush with the concrete slab, and so I need the pre-slope to zero out at the edge of the drain assembly. Is this a problem?

(2) The shower enclosure is about a 3x5, with the furthest wall from the drain being about 4 feet. My plan is to just run the same height all around, and dealing with the steeper grade at the back of the shower by the drain. So the height of the preslope at the walls would be 1 inch all around. Any reason I should not do it this way?

(3) as far as pouring the shower pan, is there any secret to it? I've watched several videos and read articles on various forums, so I get the idea of it... just seems like getting a smooth 2% grade from wall to drain is an art, and I'm worried that mine will end horribly with all sorts of ridges and flat spots.

(4) My plan is to put the 2x4s in to frame my shower curb, then just use my sand topping mix to build the pre-slope, lay the PVC liner, then the top layer of sand topping. Am I missing anything in there as far as the shower pan is concerned?

Thanks in advance. It's my first time posting, so I apologize if I posted in wrong place/wrong way.

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jadnashua 05-26-2017 07:50 PM

First, if you can, move your drain to the middle of your shower area. Why? Well, to get a consistent slope, you need to measure the longest distance from the drain to an edge...that slope should be at least 1/4"/foot...but, when it's not centered, that means it's much shorter between the drain and those near walls. Most people much prefer that the bottom of the walls are even (it doesn't have to be, but it's an aesthetic thing)...that means those shorter walls will need to rise much faster to reach a level line all across the shower.

A mudbed over a subfloor needs to be at a minimum of 3/4", and industry wants 1-1/4" thickness at the drain (it can be thinner on a slab). So, if you chose to build a conventional shower with a liner, you at least need to raise the drain.

One thing that might work if you left the drain where it is and to use a conversion drain to then make a Kerdi shower.

You need a different material to cover the curb...place some metal lath over it that was overbent to help keep it in place, then a much richer mix that will have more strength and be sticky enough to hold it all in place.

There's a good article in the 'liberry' that discusses all of this.

My preference is to make the entire shower waterproof, and that means a surface applied membrane, (better, I think, than liquid, painted on ones). That way, the whole thing is both waterproof and not just water resistant...it dries out much faster. When you use a membrane like this, you only need the single layer of mud, rather than the preslope, liner, setting bed, since the membrane is both the liner AND the setting surface. This means also that you can have a lower shower pan floor and curb while maintaining the required height of the curb above the flood plane.

dave.adams 05-26-2017 08:33 PM

Thanks for the reply. A few things:

(1) I'm trying to cut as many monetary corners as I can, so with that being said, I'd like to try and avoid both moving the drain and the Kerdi options as those are both more cost intensive.

(2) I understand the reasoning behind moving the drain, but is it really necessary? I know it won't look perfect, the steeper slope at the back wall by the drain won't really ever be stood on since the shower head is on the opposite wall.

(3) Does each mudbed need to be at least 3/4" thick? The preslope would be 1 inch think at the walls, tapering down to 0 at the drain edge. Then the top mudbed over the liner can be made as thick as it needs I assume.

My plan was to just Redgard everything before tiling to provide for the waterproofing under the tile layer.

Thanks for your help!

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gbchriste 05-26-2017 08:54 PM

Although I'm in the middle of tearing the shower my contractor started, I will add a little different perspective on the slope with an off center drain.

My design also has the drain closer to the rear wall and I considered having a level perimeter as you suggest, which would put a steep slope on the shortest run to the drain.

I didn't like it so we built the mud deck 1/4" per foot slope all the way around, which meant that the perimeter sloped downward as it progressed closer and closer to the drain. This means that the bottom row of tiles, which were large 20 X 20, had to be angle cut to follow the slope of the floor while keeping the top edge of the tile level.

I have to say that before we had to tear out due to some really crappy tile setting (resulting in the GC and tiler being fired), I really liked it. The fact that the bottom cut of the tiles was sloped wasn't even noticeable and I found the gentler slope toward the drain no matter which wall was involved to be easy to stand on.

And think about it. A bathtub/shower combo is slopped exactly that way, sloping downward from the far end of the tub toward the drain, and also from the sides toward the drain.

I see at lot of guys say the perimeter absolutely must be level all the way around. I'm just not sure that's true.

jadnashua 05-26-2017 09:26 PM

Most people prefer the level perimeter. It becomes less noticeable when the wall tile are larger, but that may or may not be your preference. A typical linear drain system does not have a level perimeter, but that single slope has some symmetry to it, which may mask the issue.

A conventional shower construction works...it's just that a surface applied membrane works better, IMHO. Keep in mind that there's no really good way to tie a liquid applied membrane to a conventional clamping drain. Should you decide to use RedGard as your waterproofing, read, understand, and strictly follow their shower build instructions.

Once you have a preslope and a liner down, the setting bed is installed so that it is all an equal thickness. But, because what's underneath is sloped, it all works. That unbonded layer needs to be fairly thick - again, industry wants a minimum of 1-1/4" thick. Some recommend less. The industry guideline is safer, not saying thinner won't work...it just has less of a chance than a thicker layer. Most mud manufacturer's instructions follow the industry guidelines.

dave.adams 05-27-2017 07:22 AM

Forgive me for being a noob, but I think I need some clarification:

(1) what is a surface applied membrane? I guess I'm confused about how to shower pan construction is supposed to work. I assumed the PVC liner was essentially your waterproofing on the floor. So after I lay the tile and seal everything, ideally all water runs on top of floor to the drain. But any that does get through to the top mortar layer would either just dry out, or get caught by the PVC liner and run to the weep holes. So what purpose would additional waterproofing tied into the drain serve, since the PVC liner is already a layer of waterproofing tied into the drain?

(2) So does the preslope need to be that 1-1/4" thick you talked about, or is that just the top layer/setting bed? Is the unbounded layer the same thing as the setting bed? I understand the setting bed should be a level thickness as it just follows the slope of the layer underneath.

Thanks for your help, sorry for my inexperience.

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CaliGrown 05-27-2017 07:50 AM

Surface Applied Membrane, is either sheet or liquid applied waterproofing. It goes directly beneath the tile and is tied into a specific type of shower drain (bonding flange drain assembly or the divot method). Only one layer of mud is required with these membranes, as the liner is no longer needed because all water that gets behind the tile is directed to the drain along the waterproofing surface.

Houston Remodeler 05-27-2017 07:54 AM

1- A surface applied membrane is a waterproofing layer applied over drywall, cement board, or your mud bed which is then covered with thinset and tile. There are quite a few choices; a fabric, a liquid, and a waterproof board which replaces the drywall or cement board.

If you are using a traditional liner on the floor, you can still use a surface applied membrane for the walls, but not the floor as you want only one waterproof layer (no sandwiching)

As for how the liner on the floor works, yes that is correct.

IMHO a liner is good 70 year old technology, but a surface applied membrane for the entire waterproofing system is superior. Liners fall down when it comes to benches and odd shaped showers, curves, and other hurdles. Further, the mud floor takes a while to dry out. If you want natural stone for the floor, the stone will appear darker where its more wet, and lighter where dryer. Some find this upsetting.

2- What substrate are you working over?

dave.adams 05-27-2017 09:13 AM

Thanks, that's very helpful.

(1) that all makes sense. I'm planning on using a marble hex on the shower floor, they are 1 inch hexagons, on a mesh backing, 12x12 total. And then I'll use a 10x14 porcelain on the walls. So what are my options for a surface applied membrane?

I suppose I'm open to using Kerdi though I was hoping to avoid the extra $500 for the kit. But even if wanted to use it, my shower enclosure doesn't fit quite right with the dimensions for a 3x5 with an offset drain. I didn't think I could cut it to fit, am I wrong?

What other options are there for a surface applied membrane? I guess I wasn't aware of other systems besides a kerdi, and how to use them properly.

(2) I'm on a concrete slab.

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dave.adams 05-28-2017 03:05 PM

So I'm pretty much all but decided on going with the kerdi option instead of the conventional method after having read several forums, and a couple of John's articles. So I have some new questions:

(1) I'm still planning on just building the pan with deck mud, since the prefabricated tray won't fit right in my shower enclosure. The drain isn't quite in the right spot, and the enclosure isn't square. At one end it's 36.5 inches from wall to end of bathroom floor tile, and at the other end it's 37 inches. If I build the pan myself with deck mud, this doesn't seem to me like it'd be a major issue, at least as far as being noticeable to the naked eye once everything is tiled and finished? I was just going to use the kerdi drain adaptor kit to attach to my clamping ring drain, then lay the deck mud pan, and use kerdi membrane to waterproof everything.

(2) If I'm going this route, what do I do for the curb? I thought I had read somewhere that John isn't a fan of kerdi prefab curb as it's a little high (6 inches I think?). Do I still just build it by stacking 3 2x4s on top of each other then metal lath, and then duck mud to shape it, then kerdi membrane over it?

(3) If I use the kerdi drain, I'll have some flexibility of height that I don't now have since the clamping ring drain is flush with the slab. So once I install the kerdi drain, my pan should be how thick at the drain? And then I'm planning to just run a level perimeter at 1 inch higher than the drain all the way around, since the farthest wall from the drain is about 4 feet away. I recognize this will be a steeper grade along some of the edges closer to the drain, and the foot or so between the back wall and drain, but since no one will really be standing there, it doesn't seem like a major concern.


cx 05-28-2017 03:24 PM

Welcome, Dave. :)

If you want to use a direct bonded waterproofing membrane (actual name for "surface applied" membranes, ANSI A118.10) for your shower I'd recommend you remove the clamping drain you have and replace it with a bonding flange drain rather than use that add-on drain. Chipping a little concrete will allow you to set the drain at the desired height and you could move it closer to the center of the shower while you're at it.

I'd recommend the USG Durock Shower System membrane as it's easier to install without any real need for pre-formed corners and with your correct choice of a mud floor you'll be able to buy everything you need on Amazon and all you really need is the roll of membrane and a drain.

You can build your own curb with wood covered in CBU or out of CMUs and apply your membrane over that in any shape or size you desire.

My opinion; worth price charged.

dave.adams 05-28-2017 09:06 PM


Thanks for your response. As for changing out the clamping drain, with the kerdi adaptor kit, as long as everything is done correctly, isn't it basically the same thing as just removing and replacing, since you end up with a bonding flange drain at the end of the day regardless?

I looked on Amazon at the durock system and it is about the same price as the Kerdi system. Do you recommend it because it's objectively better?

I'd really prefer not to chip out any concrete if I can avoid it.

As for building my own curb, that'd be the same regardless of whether I use Kerdi or Durock system right? And what are CBU and CMUs?

Thanks again for your help!

jadnashua 05-28-2017 09:50 PM

Some people feel that the Durrock membrane is easier to work with. Either one will work just fine. One advantage of busting the concrete is that you can get a view of the p-trap...they usually can last a very long time, but if yours is on its last legs, building a new shower on top of it can be a problem.

Is this a slab or a subfloor? If it's a slab, you might want to just use some concrete pavers and build your curb out of it. IF you go with wood, and moisture comes up through the slab, it can cause the wood to swell and damage your curb. CBU=cement backer unit (i.e., cement board). Depending on the room, you may or may not like the size of the Kerdi foam curb.

The preformed corners just make things a bit easier...the membrane was used for many years before they offered them. It's not all that hard to make a corner without them, but it is faster with them. Done right, either works, but you'll likely end up with less buildup using the preformed corners.

cx 05-28-2017 09:52 PM

1. So long as you've got room for the extra height of your mud bed with that drain, I suppose it's your choice.

2. Yes. It's thinner and easier to work with, 'specially when folding corners. Less build-up in those folds. Less permeable, too, which doesn't matter much to you in your application.

3. Up to you.

4. Yes. CBUs are Cementitious Backer Units or "cement board" that you would use for your walls and such. CMUs are Concrete Masonry Units such as bricks and concrete blocks of all sorts that you might use to make your curb.

[Edit] Now that I see Jim's post I gotta add that the pre-formed corners are good if you're using Kerdi, but not if you're using Durock Shower Membrane. The Durock corners are actually thicker than their membrane and I don't favor using them at all. Far to easy to fold the corners with their thinner membrane.

My opinion; worth price charged.

dave.adams 05-29-2017 07:56 AM

Jim & CX,

Early on in the project I paid a plumber to replace the shower drain, it used to be cast iron, so they chipped out the concrete and replaced the drain, so the P trap is brand new. I recognize now I should have asked the guy to move the drain to the center while he was in there chipping it out... alas hindsight is 20/20.

I am on a slab, so you'd recommend something like this (http://www.homedepot.com/p/Pavestone...99/100619496)? Just turned up on it's side?

Are these the preformed corners you are talking about? https://www.amazon.com/Schluter-Syst...=kerdi+corners

I think the height of the drain will be fine after I use the adapter, but just so I can check to be sure, how thick does the mud bed need to be at the drain? 3/4 inch, then sloping up 1/4 inch for every linear foot from drain?

If I did want to make the slope accurate all the way around and live with a perimeter that's not level, I would just cut the bottom row of tiles shorter on the farthest wall, and then have to make some angled cuts on the ones getting closer to the drain to adjust with the decreasing height of the mud bed on the walls closest to the drain?

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