How to Create a Shower Floor – Part 2

by Roger

Now that you have your curb built and your pre-slope done (if you haven’t done this yet check out How to create a shower floor, Part 1) you are ready to install your waterproof liner.

Purchasing a waterproof liner

When you order or buy your liner you need to get one large enough for your shower. The liner you get has to be at least one additional foot larger than each of your measurements. For instance, if your shower floor is three feet by five feet your liner needs to be four feet by six feet. This allows enough to run the liner up the wall behind your backerboard six inches each way. You also want to purchase two “outside” corners for your curb. These are pre-formed corner pieces to waterproof the ends of your curb after you cut the liner.

I usually order mine two feet larger in each direction. Six inches is the minimum. Specifications state that your liner must run up the wall at least three inches above your curb. So if your curb is three inches high your liner needs to run at least six inches up each wall. I usually go a foot above the curb – overbuilding your shower is rarely a bad thing.

Preparing your shower floor for a waterproof liner

Image of a sandy shower mud deck

It's supposed to be sandy!

Before you install your liner I need to say type this: your preslope will be sandy, it’s suppose to be sandy – it’s normal, don’t panic. If you have any high areas in your preslope you may want to scrape or sand it down so it runs in a flat, straight line from the wall to the drain. Notice I said typed “flat, straight” and not level – if it’s level water won’t drain.

You can scrape it down with a regular razor scraper or sandpaper – yes, sandpaper.  If there is a significantly large dip in your pre-slope you can fill it with more deck mud. You’ll need to coat the pre-slope with thinset under the patch to ensure it will stay put. Don’t get all OCD about this, it doesn’t have to be perfect. Just make sure there are no major humps or dips and water will run from the wall to the drain without problems.

The next thing to do is take a chisel to your wall studs. You weren’t expecting that, were you? You want to notch out your studs about 1/8″ up to the height of the top of your liner. This is so you can place your backerboard over the front of your liner on the wall without them jutting out at the bottom. It allows your walls to remain flat all the way down to the shower floor. You will create “cavities” in your wall studs for the liner. 1/8″ is a bit larger than the thickness of your liner but it’s better to be larger than smaller.

When you place your liner in the shower you will be folding the corners so you want to allow enough room on one of the corner studs for three layers of the liner. I usually notch my corner studs out 1/4″. This allows enough to keep your corner square after the walls are up.

Placing the liner in your shower

Image of a shower liner placed on pre-slope

Liner placed over pre-slope

Now it’s time to lay your liner in the shower and get it all lined up. DO NOT cut anything until you have the liner exactly where you want it. Make sure you have the top half of the drain flange removed before you place your liner over it. I’m not talking typing about the round part that unscrews, I mean the top half of the lower part which bolts onto the lower half. After removing the top half of the flange replace the bolts, this will serve as a guide when you cut the liner.

Center your liner in the shower with the ends running up the walls evenly. Also make certain you have enough of the liner draped over your curb so that you can attach it on the outside of the curb. I will usually place it so that the liner drapes up and over the curb all the way to the floor on the outside of the shower.

Cutting the hole for the drain out of  your shower liner

Image of the drain cut out of a shower liner

Drain hole cut out of liner

After you have it properly positioned you can cut out the hole for your drain. Do this very carefully – there is no second chance. Take your utility knife and poke a hole through the liner directly in the center of the drain. From there cut in a circular motion toward the outside of the drain in a spiral. Only cut it  out to the outside of the four bolts which attach the top half of the flange to the bottom.

Image of silicone under liner around the drain flange

Silicone under the liner around the drain

Remove the bolts from the flange. Now you need to place a bead of silicone under the liner around the perimeter of the lower flange. The easiest way to do this is to place the nozzle of the tube of silicone into the hole you just cut for the drain. Place a good size bead around the lower flange outside of the bolt holes, don’t get any in the bolt holes. This prevents any minute amount of moisture from getting under you waterproof liner. Press the liner into the bead of silicone all the way around the drain to ensure full contact.

Image of prepared liner

Prepared liner ready for top slope

Now you can bolt the upper half of the flange to the lower. Do not overtighten the bolts. You want to squeeze the liner between the two but not so much as to crack the flange – they are only plastic, after all. That’s it, the drain is finished.

Now take your liner and place it up the walls into the notches you cut out of the studs. You can nail or tape the top of them to hold them in place. Only place one nail into the very top of the liner, never lower. In the corner you will fold the liner over on itself, never cut it. Place the folded part into the larger notches. There should be enough room in the notches so your backerboard will set flush onto the studs.

In my next post I will cover how to cut the liner for your curb and make sure it’s waterproofed properly.

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Tara

We want to install this type of shower in an older home and we are a little worried about the weight of all the cement and tile. Do you think that is something that we should be concerned about?

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Brian

Hello Roger –

I’m working with a tile contractor to replace a walk-in shower. The contractor installed a proper (in my opinion) pre-slope. However, when he put the pan liner in, he attached lathe to the liner with staples into the wall studs inside the shower itself (not on the outside of the curb). When I questioned him (because he has now created myriad staple holes in the pan below the height of the curb) he replied that a water test would only need to be .5″ deep (curb is 6″ tall) and he did not put any staples that low. He also claims that he cannot apply the mud directly to the PVC liner w/out the lathe. By the way…he also installed the backer boards on the walls before putting in the pan (in other words, the pan does not extend behind and above the bottom of the backer boards). I am thinking that everything but the pre-slope should be pulled out and redone. Am I off my rocker?

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Roger

Hi Brian,

You are absolutely correct. He obviously doesn’t have any idea how to properly prepare a shower.

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Roger

And a flood test requires water to just below the top of the curb, just fyi.

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Brian

Thank you, Roger. The contractor has proposed that, after he puts in the dry pack on the liner (and brings it up to slightly above the bottom of the backer boards), that he AquaDefense the whole thing before laying the travertine. Certainly not elegant, but seems like it might work if the AquaDefense is as good as the contractor claims. I’d really appreciate your thoughts on the idea.

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Roger

No! He is mixing two completely different methods in an attempt to band-aid his screw-up. He lacks the knowledge to properly build it and will continue to install ‘fixes’ until you’re satisfied. You can not paint AD over this and expect it to last. It will trap moisture between the two waterproof layers and begin to grow mold – that’s why we call it a mold sandwich. The liner needs to be the waterproof barrier, or the AD needs to be the waterproof barrier (which requires a different installation method). You can not use one to compensate for screwing up the other.

Aquadefense is a great product, but it’s being used incorrectly here, which renders it not only useless, but may actually compromise your shower due to the mold sandwich method mentioned above.

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Brian

Thank you, again, Roger!

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jeff L.

I was advised to install a ‘dumb corner’ membrane s required by Dallas code. Have you heard of this and, is this to be installed before I put the liner or after?

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Roger

Hi Jeff,

Never heard it called that, but I assume it’s a dam corner, not a dumb corner. :D It is sold in big box stores in the same place you picked up the liner.

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Howard

Roger,

I’m doing a tile shower on a concrete slab. I am building my curb like yours with blocks. I’m doing a pre-slope with Oatey liner.
Since I’m using block for my curb and I can tile directly to that, how do I run my Oatey liner over the curb?

Thank you for your site!!

Reply

Roger

Hi Howard,

You run it up over the curb like you normally would, then the wire lath holds it in place. Read through this, it’ll describe it:

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Jason

Hi Roger, Quick question for you. I have a realized concrete pan that was done with my slab. I was planning to place the backer boards on the walls down to 1/8″ above that and then use the redgard on the walls and the pan then crest my top pan. Is this method a good way to do it? I have an odd shower shape that’s gonna be hard to place vinyl down on and was hoping this method would work for it. Thanks Jason

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Jason

It should read presloped concrete pan not realized concrete pan lol

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Roger

Hi Jason,

You’ll need to create another mud deck above that preslope in order to have a continuous plane from the floor to the wall. You can not waterproof that 1/8″ gap. After you have that slope in full contact with the walls you can use redgard to waterproof the entire thing.

Reply

Ricky Goings

on a concrete floor do I need the pvc on the walls only Im making a curbless shower. 4′ x 7′. Do I need pvc on the floor. Im using portland to create a slop 4’x4′ on the inner part of the shower?

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Dave

How flat and smooth does the liner need to be? I bought an Oatey liner from HD and it was folded a hundred times to fit in packaging. Is there a method to smooth it out or no worries?

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mike

what was the answer to how flatten the liner thanks. great website

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Rusty

Thank You…I went with your ideas and it came all together so far thanks again Wife is happy

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Fiona

Hi,

I am new to this and am trying to work out how to build a mortar shower bed on top of a concrete floor. I can follower the first part I.e. Use a watery this set rather than metal lathe and then lay a preslope, but after that I wondered if I can just use a liquid membrane rather than a waterproof liner? And if I can do I need to do anything special with the wall and floor joins?

Thanks

Reply

Roger

Hi Fiona,

Yes you can, but you need a drain made specifically for topical waterproofing. The wall and floor joints are dependent on your wall waterproofing method.

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john

do you have a post with photos showing how to fold a liner over a straight curb? my shower is three sided in a niche

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Roger

Hi John,

Is this what you’re talking about?

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Kris

Hi Roger,

This site has walked us through the start of our shower stall remodel. The existing walk-in shower has all been taken out, down to the studs, exposing the existing pre-slope underneath. I’m assuming since this existing pre-slope is in perfect condition we do not need to rip this out, too (please say we don’t have to rip this out!). Now here’s the problem. The top half of the drain flange has been removed to prepare for the pan liner. The barrel portion of this flange does NOT unscrew. It’s stuck, bonded by years of calcium or something else. If this barrel won’t unscrew, and we don’t make the new mud bed and tile the exact depth as the previous- how can we continue? We are clueless as to how to get the bottom half of the flange out of the floor to start with a whole new drain assembly. Oh, and we bought a new assembly hoping to use the top flange, but it didn’t fit with the existing bottom flange. Help would be awesome!

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Kris

I found my comment! Thought I never hit submit, but here it is! Oops!

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Roger

Hi Kris,

You’ll need to either make that mud bed the correct height for that drain, or replace the drain. Replacing the drain would be easier. Get an inside-pipe cutter and cut the drain pipe off and remove that drain, then get a coupling and a short length of pipe to install the new drain.

No, you don’t need to remove that preslope. (You HAVE a preslope??? Wow…) You can chip around the drain if you need to in order to remove the drain, then just fill it back in around the new one, but you don’t need to replace the whole thing.

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Amy

We just finished the pre-slope and there is a dip that holding the water from running to the drain. According to some sources I found, I can fill that dip by thinset as long as the thickness is less than 1/4″. So my question is would the thinset is good enough or do I need the thinset then deck mud as you state above?

Reply

Roger

Hi Amy,

Thinset will be just fine.

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Stephanie

I’m reading this in a mild state of panic.
My tile guy has over 25 yrs of experience. He helped me convert a huge walk-in closet and microscopic fiberglass shower prison cell into a 6’x7′ luxury curbless shower with 4’x4′ entry and linear drain.. The plumbing for the body sprays and showerheads is a thing of beauty.
Now, the scary part. I haven’t seen him for a month or so, he’s been ‘tied up’.
The liner in my shower is directly on the slab…the flat…flat slab. My top of my linear drain is flush to slab height. How can he possibly mud to the drain still leaving the mud thick enough it won’t crumble? And how is the pebble mosaic going to meet the drain? Thinset+mud+pebble does not equal slab flush drain.
Maybe he’s planning on a Redguard coat over the mud since that was what we agreed for the walls. Won’t that trap moisture between the Redguard and liner?
His liner install matches your description well at walls and studs but I’m just feeling a little queasy at it glued flat on my slab.
I can send pictures…I dread having to peel it off the floor, or having to remove (somehow) my linear drain.
Should I send pics?
.
HELP!

Reply

Roger

Hi Stephanie,

He may be using redgard (it would be a better option) but if he does the liner needs to be removed. If he’s using the liner it needs a preslope beneath it to aim water to the drain. The preslope can be very thin at the drain if need be, the strength comes from the top mud deck. Is the liner clamped into the drain?

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Roger

You can upload photos here

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Lane

One more question. The concrete guys left me absolutely no room to work as the lower flange was dead even with the concrete floor. After doing the pre slope that flange sits about 1/4 inch lower that the pre slope. I was informed this would be ok. Is it? I have found many workers at Home Depot and Lowes have given me incorrect information on this project. :censored:

Reply

Roger

It’s fine.

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Lane

Roger,

On question have done the pre-slope is a little rough but no humps or dips. The oatey pan liner is 48″ wide and doesn’t go up and over the curb. My shower bed is 43″x 45 What do I do in this scenario?

Reply

Roger

Hi Lane,

You need to get the proper adhesive for your liner material and ‘weld’ two pieces together to make it wider.

Reply

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