How to Create a Shower Floor – Part 3

by Roger

Well now we’re ready to waterproof your curb. If you have reached this post before reading the previous two, start with How to build a shower floor from the beginning.  Now that you’re ready to get the curb cut and waterproofed lets get it done.

And yes, I know my pictures suck – I’m a tile guy for cryin’ out loud, not a professional photographer. Until you try to balance a liner, a razor knife, a margin trowel, and a camera while trying to take a photo don’t give me any crap about it. Oh, and you can click on any of the images for a full-size version – partake in the full glory of how much my photography sucks.

We need to start by finding the inside lower corner of your shower pan and making certain that the liner is pressed firmly against it. Then follow it up the corner of the curb and wall to the top inside corner of your curb. This is the spot at which you will start the cut in your liner.

Cutting a liner for a curb when shower walls will be backerboard

Cutting a liner for a curb when shower walls will be backerboard Click to Enlarge

Deciding in which direction to make your cut depends upon how you plan to waterproof the walls. If you are simply using a cementious backerboard on your walls with a moisture barrier behind it you want to cut from that point straight up. Or, more precisely, cut your liner so that when it is placed flat against the studs the cut will go straight up from that point.

If, however, you are using a topical waterproofing membrane (that’s just fancy-ass, pinkie in the air talk for waterproofing that goes right behind the tile) I cut it a bit differently. Start from the inside top corner of the curb and cut straight out to the outside corner of the curb.

Cutting a liner for curb when using a topical membrane

Cutting a liner for curb when using a topical membrane

The reason for this is simple – to me anyway – if you are using a cement backerboard or any type of substrate where moisture will get behind your wall, you want to have as much of a liner at the ends of the curbs as possible to run up the wall. With a topical membrane such as Schluter Kerdi or a liquid such as Redgard you don’t have to worry about that. By the time any water behind the tile gets to the bottom of your waterproofing it should be well below your curb – provided you’ve installed it correctly.

On the inside corner of the curb you should install a ‘dam corner’. These are pre-formed outside corners which are glued to the liner to cover the spot where you’ve made the cut. I do not have a picture of these because I don’t use them, I’m a hypocritical bastard like that. But you should. (Use the dam corners, not be a hypocritical bastard.)

When you do glue your dam corners in you need to make sure you use the correct type of glue. Just like drain pipes – pvc glue for pvc liners and cpe glue for cpe liners. The glue WILL NOT work the other way around. Really, don’t try it, it’s an expensive lesson. Take my word for it.

The liner gets wrapped over the top of the curb

The liner gets wrapped over the top of the curb

Now that you have the ends of the curb cut we need to move on to preparing the curb for tile. Take your 2 x 4 that you used to level your pre-slope perimeter (you did that, right?) and place it in the inside corner of your liner against the curb and the floor. This ensures that the liner lies completely against the floor and the curb without air pockets or empty space beneath it. Then nail the OUTSIDE of your liner to the curb – only the outside, never the inside.

Please note: these photos were taken after my final mud bed was in place. I installed the curb last on this particular project. You can do it before or after your final mud bed is fabricated. Dealer’s choice.

Nailed only on the outside of the curb

Nailed only on the outside of the curb

To hold the liner in place over the top of the curb you need some metal lathe. Provided your curb consists of three 2 x 4′s your lathe needs to be cut into strips sized to fit over your curb from the floor on the outside to the inside bottom corner of your shower. Bend the lathe into a ‘U’ shape (length-wise) and place it over the top of your liner over your curb. Something else I do not have a photo of. Just because I’ve never taken one, not because I do it differently.

You only need to nail the liner on the outside if you have a wooden curb. If your shower is on a concrete subfloor you used bricks for your curb – right? Pay attention, if you fail the quiz later you owe me a beer Pepsi.

I have one more photo for this post and this is it. Isn’t that spectacular? It’s just to show you how I do the ends of the curb when using Kerdi on the walls. “But why don’t you use Kerdi on the floor too?” Glad you asked. It’s a very technical answer and requires you pay attention to every part of it or you may get lost in all the details. Ready? Because some people don’t wanna pay over 100 dollars for a shower drain. Whaddya gonna do?

Shower pan liner on the end of the curb.

Shower pan liner on the end of the curb.

Couple of things I’d like to point out about that last photo before you go bustin’ my chops too hard. First, the excess liner is not yet cut out. I cut it straight down the edge of the drywall there and everything gets tucked straight back into the wall. Secondly, yes, I put a nail through the liner. A foot above the curb. You can light it on fire that high if you choose to do so. (I wouldn’t recommend that, though. And no, I don’t want to talk type about it.)

Now we have to water test your pan to make sure it does not leak. Note: most cities and counties REQUIRE this to be done – don’t skip it. The test simply ensures that all your hard work is indeed correct and your pan does not leak. That’s it.

You need to plug the drain (or you’ll be there all night trying to get enough water into it) which you can do with either a $75 specialty plug, or a water balloon. You pick. You need to make absolutely sure that (and I’m assuming you chose the balloon option) the balloon is pushed far enough down into the drain to block the weep holes as well.  If they are not it will let you know that your weep holes work correctly. Unfortunately it does nothing to reassure you about the liner. If you look carefully into the drain you should be able to see the holes for the weep holes, get below them with your plug.

Then just fill ‘er up. All the way up to just a hair below the top of the curb. (take the 2 x 4 out of it first if it’s still in there) and leave it set for 24 hours. After the 24 hours have elapsed and you are reasonably recovered from your recently induced hangover, check to make sure the level of the water has not gone down. If it hasn’t you are ready to go.

Now if we could just get that elf guy off his ass to write the next post you will learn how to fabricate your final mud bed and tile that sucker. Hang tight, we’ll go get him. Check back real soon, y’all. And as always, if you have any questions at all please feel free to use the comment section below.

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Terry

You said dam corners should be used but that you don’t use them. What is your method, or not to worry, they really aren’t necessary. I’m at the point of putting my liner in but I can’t find the corners locally. I can order them online or through the stores but that will delay my project a few more days which I’d like to avoid.

Reply

Roger

Hi Terry,

You need to use them. I don’t use the inside dam corners, but I do use the outside corners on the top of the inside of the curb. The particular way I cut and fold my liner allows me to do this, but it is not something that should be done by people who don’t build showers for a living and aren’t EXTREMELY familiar with water management.

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Ross

Hi Roger,

I noticed a difference between the manual I purchased (Traditional Shower Method) and the article online describing how to line the curb. In this section part 3 the paragraph “Deciding in which direction to make your cut depends upon how you plan to waterproof the walls…” is not in the book. This part is for Traditional shower builds and isn’t in the book. (To clarify to everyone, I’m not upset, I’d buy it again and again-thought you’d want to add it in there for others.)
So…I cut my liner around the curb straight out like you recommend for topical method rather than cutting up for the traditional method. Since I am using a moisture barrier how can I fix the fact the studs around curb are exposed from the curb up?
I happen to have Reguard avail for the niche I will eventually build. One plan is to Reguard 6-9″ up the studs that meet the curb then place the corner dam. The moisture barrier would have to go all the way down to the curb now to protect this part because there isn’t a way to continue the liner over the studs. What do you think about that idea?
OR, I could cut some excess off the part that is tucked in the wall (by the curb) and use the liner glue to patch that area.
OR, maybe try and make a new angled cut up starting from previous cut allowing liner to be wrapped around studs similar to what you show in the picture. There will be an exposed “triangle” area above curb though.

Thanks for you continued advice.

Reply

Roger

Hi Ross,

I have trouble keeping all the info together sometimes. :D Thanks for letting me know, though, I’ll get that changed. You can redgard the stud, then cut the excess off the liner and glue a patch there. I would do both, I’m paranoid, though. The dam corners will take care of the ends, but the patch will give you membrane to hang your wall barrier over.

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Paul

Hello Roger,

I’m building a corner shower with a 3pc curb constisting of (2) 22.5 degree bends in the curb to equal 45 degrees. I’m trying not to cut the liner at these bends. I don’t believe they make dam corners or patches for this. I tucked the liner up against the curb and wrapped it around. I’m using or trying to use the kurb perfect but the bunched up liner in these corners is making the curb to wide for the kurb perfect to slide over. Do you have a certain way to fold these bends or do you cut the liner? Also thinking of using wire lathe now. Thought the kurb perfect would make my life easier but now thats not the case. If I decide to use the lathe, would you recommend setting the lathe in the final layer of deck mud letting it dry then complete the curb so that the wire lathe has some stability?

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Roger

Hi Paul,

I do not cut the liner there. If the curb perfect won’t fit over it I would at least use lath there. And yes, embed it into the top deck, let that cure then do your curb.

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Hailey

Hey!! My husband and I have been building our shower using your amazingly awesome instructions and everything has been perfect up until the curb and deck mud. We are using bricks for the curb on a concrete slab ~pre-slope, liner, top mud~ We used the same deck mud from the top mud on the curb with the liner and lathe, let it set for 18hrs, took the boards holding it in place off and……all of the mud came crumbling down and we have a half curb that is hollow! What did we do wrong? Any suggestions??

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Roger

Hey!!

You didn’t use masonry lime in the mud to make wet mud instead of deck mud. The wet mud mix it 5 parts sand, 1 part cement and 1/2-1 part masonry lime. The lime makes it sticky an allows it to cure to a more dense finish without pounding the hell out of it. That’s why the sides of your curb fell off – lack of beating.

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Hailey

So should we just leave the deck mud in the shower pan and remove all mud on the curb and start over from there or do we have to tear it all out and start over.. If just redoing the curb should we put thinset mortar where the wet mud meets the deck mud on the shower pan so the wet mud sticks to the deck mud or will the lime assist in this bonding.. Also what type of lime should we use

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Roger

You can just do the curb. You can use thinset, but the lime will help it stick as well. Powdered masonry lime found in the concrete section.

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Hailey

Hey mr elf everything worked great ( lime was rather hard to find ) but turned out perfect.. Now I’m ready to use this redguard put up.. We taped and bedded the wonderboard with alkali resistant tape and thinset and it looks great.. Questions .. After removing dust with damp sponge I’m planning on just start painting it on with brush and roller .. I put wonderboard on ceiling so should I redguard that also and what about the deck mud and curb should I also redguard that as well .. I plan on putting texture over the wonderboard (if you could recommend one that would be great ) on the ceiling followed by paint.. No tile on ceiling..

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Roger

Hi Hailey,

No need to redgard the ceiling. Since you have a traditionally waterproofed floor you don’t want it on the floor or curb either. You can paint it onto them about two inches from the wall if you want, though. Just any regular drywall mud will work for your texture, they all work pretty much the same except for the curing rates. A longer curing rate (i.e. the 45 minute rather then the 15 minute) would be easier to work with.

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Hailey

Mr elf .. Thank you so much for the info.. Now we are ready to tile. With the redguard on the walls and a couple inches on the floor and ceiling were ready to do this.. We picked out some glass tile for mosaqe which you can’t actually see through so I’m not sure if that matters but … We have that for an accent on walls around the body sprayers along with 12×24 tiles and 2×2 tiles for a border.. We’re painting ceiling so no tile there but doing a 2×2 on floor my questions are … Exactly what thinset is best with redguard and what trowel size and shape (v or notched ) will work best.. I’m sure we will need multiple because of the tile variations we have.. Also the deck mud has some shallow pits in it (I would say about 1/4 in deep and about 3″ round) I’m going to have to fill them with something or the floor tile will recess a bit .. What would you recommend for this.. Thank you so much your a life saver

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Frank

Hi Roger,

I’m to the point of waterproofing my curb – traditional method. My shower is in the corner with two walls, and two perpindicular curb sections. How should I handle the membrane at the 90 degree curb corner? With a cut on top of the curb and a special dam corner. Or fold tightly and clamp down with lath?

Reply

Roger

Hi Frank,

Cut right down the center of the curb from the inside corner to the outside corner, overlap the edges and glue them. Then take an outside corner and place it upside down and backwards on the inside corner (it fits that way with the circular part on top of the curb and the 90 degree corner on the inside) and take an inside corner and place it upside down and backwards on the outside of the curb.

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Frank

Thanks Roger for such clear instruction. Your books and are the best investment I’ve made in this project!

Now about the lime for the fat mud: Type N or type S?

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Roger

Hi Frank,

Wow! You have access to both? Most people can’t find one. :D Type N.

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Frank

Roger,

1. I’m reading the Redgard instructions as calling for fiberglass mesh in the plane changes for added protection. I’m not reading it as being required, but installing the mesh won’t interfere with the independent movement of my two tile walls, right?

2. I’m about to order stone slabs for the curb caps (curb has two perpendicular sections). How should I join the slabs? Butt joint, or 45 degree miter? I’m thinking the butt joint will have slight lip due to the slight inward curb tilt, and the 45 will require some precision grinding for a nice joint. Which is less painful? Am I overthinking this?

3. I’m assuming I treat the slabs as two huge tiles – bond with thin set? Leave grout joint and apply grout?

Thanks!

Reply

Roger

Hi Frank,

1. It actually is required for redgard. I don’t understand what you mean by affecting the independent movement, you don’t want them to do that.

2. No, you aren’t overthinking it. You can do either, butt joint is much easier to get lined up and flush.

3. Yes with the thinset bond, grout is up to you. You can just silicone a butt joint or grout it. Normally a matching epoxy is used to fill the joint.

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Michael .s

Hello. I have a question I purchased the underlayment same exact as pictures from home depot the one I bought was folded In a way that I have a crease in it from back to front of shower. Is this why I’m having trouble laying this down. And is there some type of glued I can use underneath to help hold it down right. Thanks.

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Roger

Hi Michael,

You don’t need to glue it down. Once you get the top mud deck on it it will lay flat.

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Porky

With a 2×4 curb, what is the nicest way to tile the top. Do you use 2 bullnose and cut them to the desired width?

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Roger

Yes.

Reply

James Richard Bailey
Roger

Thanks James!

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James Richard Bailey

Hi. I am getting some useful info from your website. Since you mentioned your photography, I thought I’d improve one of your photos that I am using. Here is a link to it on Photobucket.

http://s1208.photobucket.com/user/sancheq/media/showerlinerhowtocutforcurb_zps78138977.jpg.html

Feel free to grab it and plug it into your web page. No credit for me required. Thanks for the useful info I needed to build my own walk in shower on a concrete slab.

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Ken

Roger, I am making a shower that does not have nice 90-degree corners. I’m using Kerdi membrane w/out the shower drain kit. How do I waterproof the corners? Similar to how you did the niche with Kerdi? Your book doesn’t tell me anything about this situation, although at the end I see a shower install you did with corners that were not 90-degree angles, but there was no instruction as to how you did it. Thanks

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Roger

Hey Ken,

Just cut a flat square and push it into the corner, cut a slit from the top to the corner then overlap those two folds. The very corner will have a pinhole, you can put a dab of silicone in there if you want to, but it’ll be fine either way.

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Jon

Rodger,

Thanks for all of the great help. My only question is do you need to wait a full 24 hours for the water test, or would simply waiting overnight or 12 hours be fine?

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Roger

Hey Jon,

Once you get the pre-slope in there you can put the liner on it in about 12 hours, then do your flood test right away (or after the curing time of the glue you use if installing curb corners, etc.)

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Elias Strangas

How do I attache a Laticrete drain on concrete floor? Laticrete says to use screws for plywood, but nothing on concrete floor. How to keep the drain attached to the deck mud?

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Roger

Hi Elias,

What laticrete drain says to use screws??? All of laticrete’s drains of which I am aware are all topical drains. They install into the very top of the mud bed with thinset – that’s why they have those little triangles around the edge, for thinset to lock it down. You have your hole for the pipe, you put thinset on the mud around it and glue the drain to the pipe. As you press it down the thinset squirts through the holes around the edge, you smooth it out and let the thinset cure. It doesn’t go anywhere.

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Jamie

Roger,

I have seen the instructions (also a youtube video)that Elias is referring to, because I had a somewhat similar question. I was concerned with the idea of having the flange screwed down and not knowing if I was packing the mud bed enough underneath the flange. I definitely like what you are saying much better that is if I am understanding you correctly.
We can make our mud bed by using the flange as a guide / template leaving a little extra wriggle room. Then remove the flange and one the bed has cured go in and permanently set the flange in place with thin set?
I do have one other question though. You seem to be a stickler for following manufactures instructions, but Laticrete stipulates using “Laticrete 3701 fortified mortar bed” for my application. In your opinion… is this a sales tactic or should I be following that on to the “T”?

Once again….Thank you so much for the “Professional” advice

Reply

Roger

Hi Jamie,

They’re trying to sell you their deck mud. Why wouldn’t they? :D If they can get you to buy their bagged product rather than mixing your own they make money. I will say that their 25 year and lifetime warranties require the use of their product. It simply removes any inconsistencies. It’s good stuff, but it isn’t required (unless you want the aforementioned warranty).

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Chris

Roger,

Have you ever installed a linear drain (and some people think a kerdi drain is expensive!)? Any problems with them? it seems like it would be easier in some ways since you only need to slope the floor in one direction. The only problem may be you would need to cut your bottom row of tile on an angle to match the slope.

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Roger

Hey Chris,

I’ve installed a lot of linear drains. The only problem with them is the pricing. :D The bottom row does need to be cut to conform to the slope.

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Monica Lau

We finally put down the shower pan on the preslope and the hardibacker on the wall. However, there is some air packets around the corner areas. If we leave it as it, what would happen?

Thanks!

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Roger

If you’ve installed your top mud deck and there are air pockets you need to tuck the liner back in there further or add more deck mud and pound the hell out of it until the air pockets give up. If you haven’t done your top mud deck yet just pack the mud in there real well and the air pockets should disappear. As long as your mud is packed really well and solid they won’t hurt anything.

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Mike

Roger,

I am re-doing my shower that is on a concrete slab. I want to build a curb large enough for a 6″ piece of marble I have to cover it. Would it be ok to build the curb in two stages. First build the brick curb like you say and put the liner up and over the curb. Then build a concrete form and deck mud or concrete to get the curb to the size I want?

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Roger

Hey Mike,

Yes, it will work as long as you use deck mud (not concrete – it’ll crack).

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Ryan

Roger,

I purchased your topical waterproofing manual and have a question regarding the height to waterproof. The shower I am working with is 40″ x 80″ and 10ft high ceiling. How high up the walls should I go with Redgard or the like?

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Roger

Hey Ryan,

It needs to go a minimum of two inches above the shower head.

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ryan

If I am doing a brick shower curb how do I attach the membrane and metal lathe to the brick?

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Roger

Hey Ryan,

The metal lath is folded into a ‘U’ shape, overfolded a bit so it will spring back when pulled apart. Liner goes over the curb and lath is placed down over it. The shape of the U holds the liner in place and hugs it against the bricks.

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Donald Gendron

I am using a wooden curb and want to attach the metal lathe to it. Do I nail or staple the lathe only on the outside of the curb and the mud will hold the bottom inside of the lathe to the curb and should I install the lathe before making the pre-slope bed?
BTW, thanks for the very informative site.

Don

Reply

Roger

Hi Donald,

You need to install the lath over the top of the rubber membrane on the floor (I assume you’re doing a traditional floor – it’s the only reason you would have a preslope), that’s what holds it in place. If you bend the lath around a 2×4, then overbend it so it sort of ‘springs’ back it will hold it tightly once you place it over the liner. You can nail it on the outside of the curb if you want to.

If you are using a topical membrane like kerdi or hydroban you can nail it as much as you want, wherever you want to. Your waterproofing goes over the top of it with the topical method.

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Paul

Hi Roger,
Must say I love the site.

Does the redguard go directly on the mud pack

Thanks Paul

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Roger

If you are using it as your waterproofing for the floor then yes, it does.

Reply

AJ

Roger

Been awhile since iv made any progress on my shower (about a year to be exact). Its time to get back on it. I have my pre-slope installed along with the curb, and PVC liner. I went today to bought my cement back backerboard. I was thinking this would be my next step, but after coming to doing a refresher coarse, i may be mistaken.

I know i need to do the metal lathe over the curb and liner. But my main concern is the cement board. I thought i would install the backboards next over the liner on the walls and drop down to the base of the pre-slope. Then my top layer mud bed would press against the back board. Is this correct? Or should i put my top layer down and then put my backboard up?

Thanks for the help!!! Ready to get this thing over with and start using it.

AJ

Reply

Roger

Hey AJ,

You can do it either way. Backerboard first with the mud deck against it is easier and quicker.

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AJ

Thanks for the quick response! Im glad to know i can go ahead and get the backerboard up. Maybe it will start looking like something has been done on it.

I have a few bags of concrete mix and also a bag of keraflor tile mortar. Which should i use to cover the metal lathe on the curb?

Thanks

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AJ

Just found a bag of Type M – Mortar also.

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Roger

You need deck mud. Add a little lime to it and it will be sticky.

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Cora

I read everything and it is very clear. My only problem is that I do not want a curb when one enters the shower. Older people need to walk in on the existing floor into the shower area. where should I go for that information? Thank you.

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Roger

Hi Cora,

Google Curbless shower. You need waterproofing on the floor outside the shower as well as having the drain the farthest from the entry as you can possibly get it. The easiest way to achieve what you want is by using a linear drain against the wall opposite the entry and using a topical membrane for your waterproofing.

Reply

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