My weird shower floor

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Tyke's_Place

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Hello,

I'm hoping to get some advice on my basement shower project. Lots of reading and many questions are rolling around in my skull. But I'll start at the floor, which is a bit unique. Over the slab I have 2" of high-density polystyrene insulation, and then standard subfloor. The walls and finish floors are on top of the subfloor.

My goal is to remove the foam and subfloor where the pan will go. That's 2-3/4" thick. The pan would go on the slab. Then after the build up of the pan and tile, the shower floor by the curb will be a bit lower than the finished bathroom floor. Here's my diagram of the whole plan.



First step would be to cut the subfloor to remove material for the pan. I'd leave 14" of foam/subfloor as a base for a bench. I'd frame the bench, covering it with hardibacker to drain from the wall down to the pan. The pan membrane would come up behind the hardi at the foot of the bench, same as it will at the walls. Finally I'll install a 2" mortar bed for the bench seat. Any issues with that plan?

For the floor, I have a knockout in the slab. I plan to dig out the gravel to make room for the trap. Then install the trap so the drain is centered in the shower floor. Here's what I have now.



From my reading I think the best practice for the hole is this. After I set the plumbing and drain base, backfill the hole with packed sand or gravel to the bottom of the slab, then fill with 4" of concrete to match the finished slab.

I'm wondering about the height of the drain. I've already ordered the Kohler drain below. I think the thin flange below the weep holes should be at the level of the pre-pitch. Meaning if pre-pitch is 3/4" thick at the drain, then that thin flange on the drain should be 3/4" above the slab. Then the Oatey membrane lays over that and is clamped by the weep flange. Is that correct?

fdaba204-cb35-47a7-8108-01590490cefb_400.jpg

If so, then I really need to plan the pre-pitch correctly. I've also ordered the Kirb-Perfect Pre-Pitch and Quick-Pitch kits. Their site shows both of those kits being used for a shower pan. Both kits have 1/4" per foot slopes. So do I end up with 1/2" per foot for the finished pan?

Their directions show the pre-pitch bed going to almost nothing at the drain. But, that's with a slab and drain that are already done. I've read here and other places that 3/4" to 1" is preferred. Since I can set the drain at whatever height I want, then I can do the preferred thicker pre-pitch. Correct? Or maybe I can set the mortar bed to be thick enough to pretty much match the finished bathroom floor. That leads to my next question about the pan.

If use the Kirb-Perfect kits, each with its 1/4" per foot slope, then that's a total 1/2" per foot rise. That means I'll slope up 1" to the left of the drain, and about 1-1/2" to the right of the drain. So the perimeter of the finished pan will be out of level by 1/2" over the 5' width. Is that correct? Do I just adjust for that at the bottom of the wall tiles?

Thanks to anyone that takes the time to read all of this and provide advice. I really appreciate it.
 
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Cacher_Chick

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More than 1/4" per foot is going to feel notably uneven when standing in the shower. I think I would rethink your plan for the bench too. You have not made any mention about waterproofing the shower, but you are going to need the waterproofing to run down the walls and over the bench so all water goes to the liner and weep holes. Having any water end up on your subfloor is what you need to work very hard to avoid. This must be taken into consideration when planning your bench and curbs, all the way out onto the floor outside of the shower.
 

Tyke's_Place

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More than 1/4" per foot is going to feel notably uneven when standing in the shower. I think I would rethink your plan for the bench too. You have not made any mention about waterproofing the shower, but you are going to need the waterproofing to run down the walls and over the bench so all water goes to the liner and weep holes. Having any water end up on your subfloor is what you need to work very hard to avoid. This must be taken into consideration when planning your bench and curbs, all the way out onto the floor outside of the shower.

Thanks for the reply.

I had the same thought about 1/2" per foot on the floor. I just read the Kirb-Perfect FAQ page. I was misunderstanding. It says: "The Quick Pitch Center Ring rests on top of the flange bolts of the drain which raises the system up to allow for water to flow to the weep holes and compensate for the Pre-Pitch eliminating the doubling of the pitch.".

My understanding with waterproofing Hardibacker is that I'd put 4mil or thicker poly between it and the framing. My plan was to frame the bench so the top has the proper slope. Then poly down the walls, over the bench, and down and over the membrane. Then Hardibacker on the front face of the bench. I figured the 2" mortar bench on the top would be a solid base for the the tile there, avoiding flex when anyone sits on the bench.

I'm open to suggestions though.
 

Cacher_Chick

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For a solid water resistant construction, I would suggest making the bench out of CMU (cement blocks) and mortar. I have never heard of using poly, except as a vapor barrier. Hardibacker alone IMO will take too long to dry out, which can lead to mildew & mold, which will first become pronounced at the lower grout lines. It can be waterproofed with a topicals like Laticrete or Redguard waterproof membrane, or a sheet good like Kerdi. Your goal should be to have a completely waterproof shower that dries out quickly BEFORE you ever cut the first tile.
 

Jadnashua

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You're asking for all sorts of problems. First common misconception...tile is NOT waterproof and the shower should be watertight prior to the installation of the tile. CBU is NOT waterproof, but is generally not damaged by being wet. But, there are two classes of CBU, 'real' cement board, and fiber-cement board. The differences are that with fiber-cement board (Hardie is this type), you CANNOT embed it in a mudbed, and it can never be used horizontally in a wet location - it must be held up, away from the mudbed. Plastic sheeting underneath Hardie or any CBU is a vapor barrier only, it cannot be made waterproof, since to anchor the cbu, you must use nails or screws to hold it in place. Now, you CAN put a surface waterproofing on TOP of it, but be forewarned that Hardie is VERY thirsty, and you must be careful to apply anything to it including thinset, or it will dry out verses curing properly...thinset needs moisture to cure, and Hardie WILL suck it out if you don't treat it properly first...cbu is never TOO wet unless you see liquid water pooling on it, so dampen it very well before applying thinset or other stuff. Liquid applied waterproofing often works best to apply a thinned coat first to help seal things, then the required full-coverage coats to finish things off. I prefer a sheet membrane to a liquid, since it's hard to get the proper thickness consistently across the whole surface when you paint it on without thin spots or pinholes...not an issue with a sheet membrane.

This sort of installation begs for a surface applied membrane verses a conventional shower technique unless you make a monument bench, and then, the liner would need to come up from behind and above the top of the bench. I highly suggest you join www.johnbridge.com for some help on this, but you can ask any drain or plumbing issues here. We have plumbers, they have tilers. It is in your best interests to discuss the guts of your shower there for reliable results.

FWIW, one study I read indicated that 75% of the tiled showers built in the USA don't follow industry standards, and often fail. That can take anywhere from months to many years, but the cost of redoing it is LOTS more than doing it right the first time...they can help. The industry bible on tiling is the TCNA handbook.
 

Tyke's_Place

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Thanks for the advice. That's why I posted here.

I called the Hardiebacker company yesterday and rep basically said the same thing. The material itself if water proof, but it isn't a water barrier. For the bench his recommendation was to build a strong substrate for the bench top, such as two layers of 3/4" plywood. Hardi for the bench front, same method as the walls. Then waterproof over all of that, and 6" up the walls above the bench, with Redgard or similar. He suggested sponging the Hardi clean first, then while it's still damp, applying a primer layer of Redgard thinned with water per Redgard's directions. Let dry and apply 3 or 4 layers of Redgard.

I'm still trying to figure out the floor too. I'm calling Mark E about their pitch system today. I'll also join johnbridge.com. I'm still at the decision and design stage. I might just skip the bench altogether. I'm not totally confident that the benefit of it is worth the trouble.
 

Jadnashua

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A bench in a shower is a nice feature, but, it needs to be built properly AND waterproofed! That is much easier said than done. You do need, IMHO, a surface applied waterproofing to do it justice. Surface waterproofing does a lot of things, mostly ensuring that there's very little to get wet. To be called porcelain, it cannot absorb more than 0.5% moisture, and depending on the grout you choose, that could be impervious (say you choose acrylic or an epoxy grout...therefore, there's very little to get wet, and any moisture that is absorbed, can dry out quickly.
 

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Thanks for all of the suggestions. I've decided to go with Laticrete Hydro Barrier for the water proofing. But I think I'm also going to skip the bench. I like the idea of the bench, but this isn't a huge shower. I mocked up the bench with some cardboard. It would either need to be under the shower head or in a corner. It felt in the way of my feet under the shower head. In the corner by the entry it had to be small enough that it wasn't more than a footrest.

So now that I'm looking at waterproofing with Laticrete, I'm questioning the value of the pre-pitch and liner under the main mortar bed. If I do the pre-pitch and liner, then I guess I don't need to put Laticrete on the floor. But if I do apply it, then is the PVC liner really necessary? Should I consider the liner to be good backup insurance against the Laticrete possibly leaking at the pan?
 
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This is all new construction right? Have you considered Schulter-Systems wet room materials? They have everything and I mean everything that will solve every problem discussed here.
 

Jadnashua

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Every company has their tested, approved methods to build a proper, long-lasting shower.

Generally, when you use a surface applied waterproofing membrane, you do not use a liner like you would for an old-style one (conventional). You usually also need to use their drain assembly. In a smaller shower, a suspended bench can often work well since when facing it, your feet can extend underneath. Something like KerdiBoard can be used for this, or check out

http://innoviscorp.com/better-bench

I used one of these when I built a shower for my mother.
 

Cacher_Chick

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Much would depend on the drain that you use. A topical waterproofing such as thd laticrete cannot be made to seal to a clamping drain.
You need to choose between traditional pan construction or using a membrane system such as Kerdi, which uses it's own specific line of drains.
 

Tyke's_Place

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I've already purchased this Kohler flanged drain from Home Depot. I suppose I could return it.
fdaba204-cb35-47a7-8108-01590490cefb_400.jpg

Then I could skip the pre-pitch and integrate a Laticrete waterproofed pan with a Hydro Ban drain, like this one. Correct? I'm looking at this page.


I've looked the Kerdi products, but I'm on a budget, and Kerdi seems to add up pretty quickly. I suppose all of the Laticrete stuff can add up too though.

Thanks for the Better-Bench link. I'll look at that too.
 
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Jadnashua

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Yes, you can do that. The drain you have is a clamping drain, designed for use with a preslope, liner, setting bed. It's simpler to use a bonded membrane drain with surface waterproofing, since you only need that one layer - your preslope and setting bed are then the same thing. Suggested retail and street prices are often not the same thing, so depending on how willing the seller is to move material, your prices between various companies may not be all that much different. I have heard good things about both Kerdi (which I've used) and the new (mid-2014) introduction of the Hydroban sheet material. THeir liquid has been around for a long time, but they just started to sell the sheet - Kerdi has been available now for over 25-years - long track record. Either works when installed properly.
 
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