The following five-part series gives a basic overview of building a shower floor for tile. If you would like a complete step-by-step of the entire process with all the little idiosyncrasies and details I now have manuals describing the complete process for you from bare wall studs all the way up to a completely waterproof shower substrate for your tile.
If you are tiling your walls and floor you can find that one here: Waterproof shower floor and wall manual.
If you have a tub or pre-formed shower base and are only tiling the walls you can find that one here: Waterproof shower walls manual.
Curb and Pre-slope
Properly built shower
There are a couple of options to create a shower floor for tile using deck mud. The first is a single-layer shower floor which can then be coated with RedGard or a similar product or covered with kerdi to waterproof it. The other is a normal shower floor with a liner which will have two layers – a preslope, the liner, then the top slope which is then tiled. This series of posts will describe the latter.
Before we start I should note that unless you are using the kerdi waterproofing method or utilizing a liquid membrane as your floor liner you should not have the backerboard installed in the bottom part of the shower. Your waterproof membrane for a shower floor will be installed behind your backerboard. The curb and pre-slope need to be completed before installing the lower wall substrate.
Creating the curb for a wooden floor
The first thing you must do is create the outside curb of your shower. You need to create the “box” which will become the inside of your shower floor. Depending upon whether your shower will be created on a wood or concrete floor will dictate what material you use for your curb.
If you have a wooden floor you want to use regular dimensional lumber. The 2 x 4’s they carry at Home Depot – those. That is the easiest and most readily available material. Ideally you want to use kiln-dried lumber. That is lumber that is, well, dried in a kiln. By removing moisture in this manner the moisture content of KD lumber is normally between six and eight percent compared to regular dimensional lumber at close to 15%. Why does that matter? Well moisture and wood don’t mix. As it dries wood has a tendency to warp and twist. The less moisture initially in the wood the better. KD lumber is best and regular air-dried dimensional lumber is also acceptable. NEVER use pressure treated lumber – ever.
I usually use three or more stacked 2 x 4’s to create my curb depending on the size of the shower. Simply screw the first one to the floor (with correct non-corrosive screws), stack the next one on top and screw it down, and so on until the desired height is reached. That easy.
Creating the curb for a concrete floor
Using Bricks for a shower cub
For a concrete floor you want to use bricks. Yeah, bricks. Just stack ’em. I use gray concrete bricks (no holes) and stack them two or three high for my curbs. You can use just regular thinset to adhere them to the floor and to each other. Just stack them in the shape you want.
You do not want to use wood for your curb on concrete. Wood will actually absorb moisture from your concrete and start to swell.
Creating the pre-slope
This is one of the steps most often skipped by a lot of people – amateurs as well as professionals. It is imperative! You need it – it’s that simple. Without a pre-slope your waterproof liner will lay flat on the floor. This does not give water anywhere to go. It will sit there, stagnate, mold, . . . you get the idea. With a proper pre-slope any water will drain to the weep holes in the drain and go where it needs to – away.
Lathe installation for wood floor
You need to first make sure your shower floor will stay where you put it. On wood you can use regular metal lathe.
You need to place what is called a ‘cleavage’ membrane beneath your lathe. This is just a sheet of plastic or tar paper stapled to your wood floor first with the lathe placed over it. The membrane does not make anything waterproof! If someone tells you that hit ’em in the head with a bat. It is necessary to prevent the wooden floor from sucking the moisture out of the pre-slope prematurely causing it to cure too fast (or not fully) and significantly weakening it.
When your membrane is down staple the lathe over the top of that. Just cut it to the shape of your shower floor and lay it flat on the floor and staple or nail it down. This gives your mud bed something to grab onto. In the above photo I have used plastic as my membrane and only have a partial piece of lathe in – make sure you cover the entire area below your pre-slope.
A properly prepared pre-slope
For a concrete floor you need to mix up some regular thinset except you need to mix it “loose”. That just means you need to add a bit more water than the instructions call for to make it thinner. Cover your shower floor area with this before you start installing your deck mud. The deck mud itself does not “stick” to anything, you need to supply something that will adhere it to your substrate.
Oh crap – Math???
To make the installation easier you’ll want to mark your height lines on your wall studs. To figure out how high it needs to be off the floor you need to figure out your slope. This involves a bit of math – don’t panic! It’s easy. Figure out which corner is farthest from the center of your drain. Your slope needs to go up in height 1/4″ for every foot. If your furthest corner is three feet from your drain center your slope needs to rise 3/4″. Easy enough so far, right?
Your finished floor (after your liner and top mud bed are installed) needs to be 1″ to 1 1/4″ thick at the drain. So, if we make the pre-slope 3/4″ thick at the drain it needs to be a total of 1 1/2 inch thick at all your walls. So mark a line 1 1/2″ from the floor all the way around the wall studs. This will be the height of your pre-slope at the walls. I try to make my pre-slope the correct thickness at the drain so it will be 1 1/2″ at the walls. This way you do not need to draw lines, just level your perimeter with the top of the 2 x 4 studs along the bottom of the wall. Depending on the size of the shower it doesn’t always work, but it saves time if you can work it out that way.
If your shower is not a square, and they rarely are, you still need to have the same thickness at the walls all the way around the perimeter. This means that you will have a steeper slope on the walls closer to the drain. This is normal. If you don’t do it this way you will have uneven tile cuts at the bottom of your wall. By doing it this way you will ensure a level line and, in turn, a level floor around your perimeter.
The height of your pre-slope at the drain can vary. It needs to be level with the top of the bottom flange of your drain. Regular drains have two flanges which bolt to each other. The pre-slope needs to be at least level or a touch higher than the bottom flange. Your liner then goes between the top and bottom flange to utilize the weep holes in the drain. This allows any water atop the liner to drain. The pre-slope supports the liner so it needs to be level or above every point of the lower flange. Does that make sense?
This is why planning is so important. Your drain needs to be high (or low) enough and your curb needs to be higher than your shower floor – naturally. So figure all this out before you build anything.
Playing with mud
Now we need to mix up a batch of deck mud. Check out that link, I’ll wait . . .
Okay, once your mud is mixed up you want to start packing it in there. If you are going over concrete and have your thinset slurry down, cover the entire bottom of the shower floor first to ensure the entire base will stick. If you have a large shower only spread as much thinset as you can reach over at a time. Start at the walls and pack your mud down really well – beat the hell out of it. Seriously, beat it like the last DMV employee you spoke with. You want to eliminate any voids and create as dense a bed as possible. Don’t worry, it won’t hit back.
Pack it down around the perimeter to just above your line. When you get that done get yourself a 2 x 4 about 18 – 24 inches long. Lay that on top of your mud bed against your wall and tap the 2 x 4 down with your hammer until it is even with your line. This ensures a level, even line all the way around your perimeter. Perfect! Now don’t touch the edges.
Properly prepared deck mud
Continue to pack mud into your shower base all the way from the perimeter down to the drain. You should have a straight line from the perimeter to the drain without any dips or humps. This will allow water to drain correctly without pooling anywhere. While this particular layer of your shower floor does not have to be exact, you do need to make certain it is fairly flat in regards to the line from the perimeter to the drain.
Ensure a consistent slope
That’s it. When you get it all packed in there it should have a shape similar to a very, very shallow bowl. Now leave it alone. Really, leave it alone. The next day it will be ready to install your liner and all that fun stuff. Don’t play with it until then.
In my next post I will show you how to install your waterproof liner. Until then leave your pre-slope alone. It’s fine. Quit trying to perfect it. We’ll do that tomorrow. Get away from it. Really. Stop staring at it . . .
Read this next if I haven’t already bored you to death: How to create a shower floor Part 2
Hi Roger,
I think your tutorials are great! I have read through all of your “How to create a shower floor” and many other posts. As a DIY’er reading your posts gives me condifence to do it myself.
I was planning to go with your full mortar bed method but then was introduced to the Noble pro slope pre-built floor at the tile store. What do you think about their pre-built products? Thanks in advance for your reply.
-Phi
Hi Phi,
I don’t use them and haven’t used that particular one. The guys I’ve talked to that have used it (professionals) say they work just fine. Most pros you find will prefer to do a regular mud bed – I do. But for DIY’ers the pre-built products work just fine.
Thanks again Roger!
Thank you!
one more simple question, and I’ll stop bugging you. Before I make the pre-slope, on a plywood subfloor, I know I need to put down paper, or plastic, before the metal lathe. What specific product am I looking for as far as paper or plastic?
I found rosin paper, but I didn’t think that was the correct stuff, and I didn’t know if I can just use standard drop cloth type plastic, or what I need.
Hey Brent,
You aren’t bugging me.
You can use roofing felt or similar or regular drop cloth type plastic works as well. The purpose of it is to prevent the wooden subfloor from sucking moisture out of your deck mud prematurely and weakening the mix. That will lead to a less stable finished product.
Thanks!
Roger-
Thank you again for the excellent tutorial ! I read that a piece of tar paper is good to have between the pre-slope and the liner for homes that experience excessive lateral movement. The home that I live in was built on a mountainside on top of a swell so the home is does move over the long term. Can you advise on the topic. Thank you again
Hey Derk,
You can put it there if you want. No real reason to provided your deck mud is mixed correctly, but it won’t hurt anything. It will assist in uncoupling the liner from the pre-slope, but that shouldn’t be a source of problems anyway. Entirely up to you. I’m a lot of help, huh?
Roger,
I am working on a shower floor over an existing flat and level concrete slab (basement).
Per your directions below, do you put metal lath over the thinset prior to installing your deck mud preslope or is it simply just a layer of thinset?
“For a concrete floor you need to mix up some regular thinset except you need to mix it “loose”. That just means you need to add a bit more water than the instructions call for to make it thinner. Cover your shower floor area with this before you start installing your deck mud. The deck mud itself does not “stick” to anything, you need to supply something that will adhere it to your substrate.”
Great site!
Thanks for info,
Tim
Hi Tim,
There is no need for metal lath in a pan over concrete unless the shower is huge – I mean larger than 10 x 6 feet or so. In that instance it would strengthen the mud. The purpose of the lath for shower floors over wood is simply to bond the mud to the wooden substrate. The lath is nailed to the wood and the mud cures around the lath – the floor is attached. Over concrete the thinset serves the same purpose – no lath needed.
So apply the thinset layer, let dry????, and then start the mudded “preslope”?
No, apply the thinset and install the pre-slope over the wet thinset. As the thinset cures it will lock it onto the concrete. You want the thinset wet as you are installing the deck mud.
Dear Roger,
Just curious; what horrible problems will I have if I use PT lumber as a curb base on concrete floor, as opposed to brick curb?
Thanks.
Hey Don,
As the bottom portion of the pt wood remains stable due to moisture content in the concrete the top portion of it will begin to dissipate the infused moisture leading to differential expansion and contraction.
Now in English:
It’ll twist.
when I had the shower put in ,it had to be flat for a wheelchair. He passed away now I wish to have a ridge to step over because the water is running out on the floor. I ask the man to put up something to keep the water in. The floor is tiled all over the floor. It has to be something to stick to the floor. What would you suggest?
Hi Nell,
About the only way to have a curb on your shower over the existing tile is to have him build a curb or ‘ridge’ out of either a styrofoam product such as the kerdi curb or kerdi-board and tile it or build one out of cement bricks epoxied to the existing tile and tile over them. Anything short of epoxying it to the existing tile would not effectively waterproof the transition. Either of those options would work well.
Roger,
I have demoed my fairly large (~15′ x 16′ with 9′ ceiling) master bath back to the studs in most cases and down to the slab (here in Austin, there aren’t too many other types of foundations), built new stud walls, rewired, installed lighting, and re-plumbed where needed. I also took up the old tile and used SLU to level everything as well, and have purchased the HardiBacker to use on the walls in the shower, around the tub, and around and behind the new vanities. I still need to buy some regular drywall to do the new stud walls and some patches in the existing walls and ceiling, but things are moving along pretty well.
My plan is to have a curbless entry 4′ x 6′ shower, floored and walled on two adjoining sides with the same 16″ x 16″ sealed limestone tile as on the floor in the rest of the bathroom, with the two other walls being floor to ceiling glass with a narrow slot/trench drain running down the inside length of the front glass wall (~3.5′) and across the doorway gap (~2.5′) of the overall shower rectangle.
My question is regarding the shower, of course! I was planning – after finding your excellent article on Red Garding a shower – to use this product on top of my hardibacker walls and – I hope – on the floor of my shower. As described above, the shower is 4′ x 6′, and I planned to slope it @ 1/4″ per foot from the back (tiled) 6′ long wall to the front glass (and doorway gap) 6′ wall so that it would end up at the height of the rest of the floor. This should provide a uniform ‘falls’ of one inch from the back wall to the doorway and glass wall, and all the water would go into the slot/trench drain running along that glass side wall and the doorway opening. The drain I am considering is itself sloped internally along its length to provide the necessary drainage angle and has an outlet I can connect (with appropriate slope, of course) via a short drain pipe to the existing drain and trap line.
The reasons for doing it this way basically boil down to not wanting a curb so as to provide a visual/aesthetic continuation of the limestone floor used in the rest of the room. In my research, I could not determine any other way to slope the large 16″ x 16″ tiles (without cutting them) while using a standard central drain to allow use of them on the shower floor.
So, my questions are, 1) does my plan sound reasonable, 2) do I still want to use deck mud to build the back-to-front sloping plane (rather than bowl-shaped) pre-slope for the shower floor, and if so 3) is Red Gard still an appropriate material to paint this slope with? I guess a 4th question is do you have any thoughts about any other way to accomplish what I want (zero curb, use of large limestone tiles on the shower floor, etc.)?
Please let me know your thoughts. I have learned a lot from you site already and want to commend you on your efforts.
Hey Tim,
Nope, no other way to do it with large format tiles. Trench drains are awesome! I love them. You will still use deck mud to create your slope. Redgard can be used on the floor with the appropriate mesh reinforcement at the changes of plane and around the drain. A better option for the liquid would likely be Laticrete hydroban – you can use it on the floor and walls as well but you don’t need the reinforcement. Not sure which particular drain you’re using but both noble and schluter make one specific for topical membranes – you can paint right onto the fabric which is already attached to the drain.
Speaking of the awesomeness of trench drains, what do you think the demand out there in the real world would be for a do-it-yourself trench drain kit and/or set of instructions? I got tired of all the difficulties of getting exactly what I wanted for my particular application located or made, as well as the unreasonable expense of all of the commercially available products and custom built ones, so I made my own. Thought if others looking for an affordable solution wanted an alternative, I could save them some money and maybe make a few bucks as well.
I had looked at a lot of the designs the commercial guys were offering, and all they are is a fairly shallow channel with a sloped floor you set into your shower floor. I had a flash of insight while walking through one of the big box stores where I noticed products that are basically PVC trim wood, and realized that if drains are constructed of PVC, I could likely build what I needed with my middling carpentry skills and some PVC solvent and cement, which after some careful planning and measuring, I did.
It all came together nicely, and – except for getting a bit of a headache from the fumes – wasn’t very hard to do. Plus, it got me exactly what I needed and allowed me to position the outlet at the best point for a straight run over to where the original drain line is. And, in my case where I am installing into a slab and want to minimize the amount of concrete I have to remove, the drain is only as deep as it needs to be – i.e., ~ 1/4″ deep per foot of length needed from the point furthest from the outlet plus a little for the material thickness, etc. The one limiting factor in my design is that there are no custom grate/strainer options – the way I did it is with a grate/strainer made of tile set into a holder with slots on either side for the water to enter, very similar to what you see at http://www.quickdrainusa.com/gallery/thumb/601085327_Hiden%20Drain%20Detail.jpg
What say you, Roger the Floor Elf? Any thoughts?
Hey Tim,
The commercially available products are expensive for a reason. When dealing with plumbing, a factor that can literally destroy a home, there needs to be codes and standards in place for those products to ensure that they will last long-term without damaging the structure. Many years and a shitload of money goes into simply getting an IAMPO certification, it isn’t easy. And if it doesn’t have that certification it can not legally be installed in a structure. With that said, you can do what you want in your house but think about little things like the pvc solvent and cement – are they going to last and hold that together for 30 – 50 years without giving way even the tiniest bit? Water is destructive – very destructive, it carved the grand canyon. These things would need to be tested and proven and certified before you could even sell them legally. Even at that point you are responsible for the integrity of that product long-term. Saving a few bucks is great, but you need to make sure that’s actually what you’re doing.
Don’t mean to piss on your parade.
Roger,
All good points you made above. Not to pick nits, but PVC pipe, solvent, and cement are used in constructing all the drains in my home today, as far as I know, and they passed all the fairly rigorous city inspections needed when they were building it (I know because I was always touring the construction site and seeing all those inspector sheets all over everything…).
But, I guess I am a little less concerned than some folks would need to be in that my trench drain will be buried in a cement slab and so any tiny give will have pretty minimal impact, actually, but I take your point: I wouldn’t want to offer my solution to others because I would sure feel bad if the thing gave way in their situation and caused loads of damage.
So, not to worry – you didn’t piss on my parade at all. You actually probably saved me doing something I would potentially regret later, so no worries. I am willing to take the risk (minimal, in my opinion because I know I built it very tight and proper) in my case, but I hear you loud and clear: if things go south, I have no one to blame but myself.
Your website is an absolute God-send!!! I love reading it even when I’m not working on a tiling job just for your great sense of humor.
I’m in the midst of remodeling my master bath. I’ve gutted the room to bare studs (just the wall kind not the human kind) and bare plywood subfloor. I’m ready to put down the cleavage membrane, a.k.a. plastic, and metal lathe and build the preslope after having screwed down the 3 2×4’s for the curb. Here’s my question- how far above the subfloor should the bottom of the three-part drain be? In other words, how high should the bottom flange (the part the bolts screw into) be above the subfloor? I have a PVC drain pipe that is nearly flush with the subfloor which results in the bottom flange of the drain being elevated 2 7/8 inches above the subfloor. The P trap is sound and impossible to get to without cutting up the solid subfloor so I really don’t want to go down that path!
Hi Kathryn,
I read my website for my sense of humor too!
Glad to hear I’m not just a narcissistic ass.
2 7/8″ is way high. You can have it at whatever height you need but keep in mind that the bottom of your preslope will need to be that thick. As it is you would have a 2 7/8″ preslope at the lowest point – that’s huge. You’re gonna end up with a four foot shower deck if you keep that up.
I usually screw the bottom flange directly to the subfloor. You can go a bit higher than that if you want to. Get an inside pipe cutter from Home Depot or Lowe’s. It slips right into your drill and looks like a drill bit with a circular saw on the end of it. Stick that down into your drain and cut about 2 – 2 1/2 inches off of it. Then your bottom flange will be right at the subfloor.
Better yet, get you one of them human studs and make him do it for you!
Roger, you said “I usually use three or more stacked 2 x 4′s to create my curb depending on the size of the shower.” Do you use more than three for a larger pan or for a smaller pan. I have a very small pan area, 30″x30″, and the three 2x4s I have down now seem to be good. As I’m typing, I think I answered my own question. If you had a shower pan that was let’s say 18’x18′ (yes, feet) then you would need more since you need a slope of 1/4″ per foot, right?
Thanks Roger. My wife and I love your website. Very informative.
Randy
Hey Randy,
Yup, you answered your own question.
As long as your curb is high enough to compensate for the height the shower floor needs to be it can be as short or as high as you want. I find that the smaller showers usually look better with smaller curbs. In your example (18′ shower) you would need to have a higher curb to allow for the height of the shower floor. Even in that example, if the drain were centered, your curb would only need to be 3 1/2″ high, so 3 2×4’s would still be sufficient.
Thanks Roger. Yeah, I didn’t think about the drain being in the middle when I used my example. Anyway, thanks for the help.
Randy
Hello,
Thank you for the informative website.
My plumber put in a pvc liner on top of my subfloor and sandwiched a traditional drain at the drain hole. Until reading your article, I thought tht only single layer mud pans were used.
Your articles do not describe a single layer shower mudfloor because if I get water beyond a topical moisture barrier, the water will not drain properly across the flat pvc liner? You do not recommend a single layer mudfloor or if so with what details being met?
This is new construction and the drywall is up preventing me from accessing the plumbing at the second floor if I would need to modify the drain from bellow for a two layer mud bed. The first floor bath is on a crawlspace.
If the lower portion of my traditional two piece drain can be unscrewed up, then I can adjust the height to accept the first mudbed, then cover with membrane, then screw on the drain. I can afix the membrane and water test before proceeding to the second mud layer.
So is this possible and recommended?
Thanks
Hi Gene,
The only time a single layer mudbed is used is with a topical membrane such as kerdi or a liquid waterproofing like redgard. If you are using a pvc liner you need a double layer mud bed with the pre-slope running from the top of the bottom flange to the walls then the pvc liner is sandwiched between the drain flanges. Your top mudbed is then created on top of the liner for your tile.
The water will not completely drain if your liner is flat on the floor. You do not need to raise the bottom portion of your drain, just run the pre-slope from the top of the bottom flange up 1/4″/ft to the wall, it doesn’t really need to be a specific thickness. As long as the overall mudbed when your done is 1 1/4″ thick you’ll be fine. You need the pre-slope if you aren’t using a topical waterproofing membrane.
Roger,
I also emailed you regarding my mold problem so forgive me for the redundancy.
I am hoping you can help me. I am re-doing another shower as well as tiling the floor and when I peeled away the linoleum I found about a square foot of (what looks to me, like..) mold. A larger patch on one side and a smaller on the other.
Please tell me theres a quick and easy way to solve this (and avoid in the future) problem.
Thank you!
– ‘Moldy’ Jon
Hiya Moldy :-)
I also emailed you my response so forgive my redundancy.
The key to mold control is moisture control. The quick and easy way to solve it is to scrub the mold off of the wood with regular laundry detergent and water and let it dry out thoroughly. Once it is completely dry the mold will be essentially dead. So that eliminates the mold which is currently present.
The way to avoid it in the future is to first understand why it happened. See where the mold problem is? Right on the edges of the shower where water will collect periodically simply by getting in and out of the shower. This water, over time, made its way beneath the linoleum and into the wood. Once the wood was wet and mold spores made their way there it simply sat and multiplied. The fact that the covering of linoleum is fairly waterproof it would not let the water beneath it evaporate. This is a perfect breeding ground for mold – as you can see.
Since you are replacing it with tile it will no longer be a problem. As long as you have a proper substrate beneath the tile and seal up the edge along the curb no significant amount of water will get beneath there. Any that does will do so through the grout lines and will evaporate back out. It will never have a chance to sit and fester. Tile is always better than linoleum. I know I’m biased but now you see why. Just sayin.
By the way – good lookin’ curb. Don’t forget to sign up for TileTips.
Regarding your recommedation to put down thinset on concrete floor before laying first layer of pre-slope with deck mud…should I put the thinset down on entire floor, let set up, then go back and cover with deck mud…OR…should I only put thinset down on as much area as I’m working with the deck mud? i.e., I’m worried about working over a large area and stepping on the thinset. We have an unusual 8′ by 4′ shower.
This is a beginner’s question from a beginner.
sorry…I asked a question before I read all the posts…you have already answered my question. You are too good!
Hey Russ,
Glad I could help!
If you have any more questions please don’t hesitate to ask. I’ll give you a professional answer from a professional beginner.
hi roger. I am tiling my shower with two preslopes. Is it better to have the plumber install the drain first and leave it up 1 inch off the plywood?. He said I can put it in and he can hook it up after but im not sure, thanks
Hey Colm,
Yes, it would be easier to have him install it first. You can then get in there and adjust the deck mud to whatever you need. If he installs it afterward and something doesn’t match up or needs to be adjusted you’re tearing out tile. Tearing out properly set tile makes me sad. If you installed it it would make you sad too.
It may work but why take the chance? Adjust the tile to the drain, not the other way around.
hey roger, thanks for taking the time to read my mail. I figured that but hes just so argumentative. So heres what he did after I explained to him I needed at least an inch from the plywood. He screwed the drain directly to the floor and tried to tell me I could lay the rubber flat on the floor.” I’ve never seen 2 mud jobs in 20 years plumbing”. Bit of a cowboy If ya ask me. I gave him the chop. I have one more question. Whats the best way to waterproof a bench that runs at 45′ in one corner?. Do I need to mud it like a shower floor or what. Thanks man. Great to have a pro to ask. Its not as easy as it looks to tile but I like to research and do it the right way.
Hey Colm,
Another “I’ve been doing it this way for 20 years…” Yeah, they’re fun.
I prefer topical waterproofing membranes such as kerdi or a liquid like redgard or hydroban for benches, niches, etc. Just makes it a lot easier. With those you can just frame them up and cover them with cement board then install your waterproofing on it. You can also use cement board with a moisture barrier behind it but I don’t recommend that – too many things can go wrong without an exacting method.
You can also build it out of cinder blocks or bricks (inside your shower pan) and use thinset to stick it all together. You can just create the 45 in the corner with a row of cinder blocks then fill up the area behind it with concrete or deck mud to the top then just install tile to it.
I have removed the tile, floor and walls from a 50’s bathroom and plan to replace it and would like to use Kerdi in shower area, floor and walls and ditra on the balance of bath floor area. The wall studs are solild and true but the floor in the non-shower area of the bathroom is poor with places where the concrete surface was damaged from the removal of the old tile and one inch thick mud bed. Some of these damaged areas are 8-10″ square and 5/16″ deep.
First I would like your recommendation as to the material to use on shower walls, drywall, greenboard, cement board???? Whatever I use will be sealed with the kerdi material.
Second, what would you use to level the concrete floor area before appling the ditra and tile?
Thank you, Ed
Hey Ed,
Believe it or not regular old drywall is the recommended substrate for kerdi. (Also what I normally use)
As far as your floor with areas that deep in certain spots you would probably be better off using a self-leveling cement product to level it out before installing your ditra. Most thinsets allow only a MAXIMUM build-up of about 1/4″ and mud beds need to be a minimum of 1 1/4″. SLC would be your best bet.
I have poured a new concrete slab next to an existing slab thereby extending the bathroom floor area, in this new area I left a recess of 61″ x 48″ X 2″ deep with a center drain for a new shower. Three of the new surrounding walls are new frame construction and the fourth is concrete block, this was the existing exterior wall of the bathroom. I have removed a section of the block wall 37″ wide, this was the width of the existing window, to allow entrance to the new shower. This area is 37″ X 10″ X 2″ deep ( the 10″ is the thickness of the block wall plus outside stucco and on the inside a thick tile bed including wire mesh, all of which has been removed) It was/is my hope to allow a direct wheelchair roll into the shower area from the old existing slab into the new shower. Clearly I did not recess the slab area deep enough to build a preslope, then liner, then mud bed and finally tile. All tile has been removed from the original bath floor. If I have explained this well enough, you can see (read) that it was my hope and intent that the new tile floor in existing bath would transition through the new opening in the block wall into the new shower area. Can I build a mud bed and use a liquid or fabric sealer and set tile directly on that surface? If so, do I use anything between mud bed and recessed slab? If you have a solution, please answer all the other questions I should have asked as well. I recognize I am late in asking but any advice/solution you can offer would allow an old man to save face and an old woman to get her wheelchair into the shower. I have been fairly handy over these past 62 years but most of my projects have not been set in stone/concrete!!
Thank you, Ron
Hi there Ron!
Quite a project you have going on there. You can indeed use a liquid or fabric membrane (topical membrane) as your waterproofing. The first thing you will need to do is get a hold of a Kerdi drain – just google that. It has a wide flange to which you attach the fabric membrane (kerdi) and it is a one piece drain so you don’t need to worry about the weep holes and all that boring stuff. It’s fairly straight-forward. It will set you back about $100-125 but it’s definitely worth it. You can also utilize it for a liquid membrane.
If you choose a liquid membrane you need to read all the directions about the particular product to see whether or not you need to utilize fabric at the plane changes and around the drain and whether you can even use it as waterproofing on your floor. Each liquid has different standards. I would use Kerdi instead if it were mine.
You should mix up some thinset ‘slurry’ (that just means mix it up thinner than normal) and place it on the slab before installing the deck mud. This will hold it in place and attach it to the slab. Other than those two things just make your mud deck as normal. Slope it from the entrance down to the drain like one big pre-slope at 1/4″ / foot then, after it cures, install your topical waterproofing membrane. Just make sure your doorway is the highest (or level with the highest) edge around your shower perimeter and run your kerdi through the doorway and under the floor tile a bit into the bathroom.
If you have any more questions please don’t hesitate to ask.
Hi Roger,
We’re building a house and I’m getting ready to start building the shower pan.
I’ve read all of your instructions (excellent, by the way) but our subfloor is odd and I’m not exactly sure what to use under the preslope…let me explain. On our Advantech sub floor we screwed 2×4 sleepers 12 in on center, ran the Pex tubing between the sleepers and filled the voids with cement leaving us alternating strips of cement and wood. Therein lies my problem-do I follow the instructions for building over a wood floor or cement floor?
We’ve tiled kitchen and bathroom floors so far and what we did there is put cement board down (using thinset and screws) and then tiled over it.
…so my ideas so far are to either do what i just described and then put deck mud on top of the cement board or another thought was to put tar paper down then staple wire mesh to the sleepers and then put the deck mud on that. Any thoughts? Am I totally off base?
Also, I’m not sure if I should be using brick or 2x4s as the curb.
Thanks,
Kim
Hi Kim,
You aren’t off base at all. You can actually do either but if it were me I would probably go with the cement board option. That way you would have a consistent base beneath your pre-slope (rather than alternating wood and concrete). If you go that route use 2 x 4’s for your curb.
If you go with the wire lath make sure you put plastic or roofing paper beneath it so the concrete and wooden sleepers do not leech the moisture out of your deck mud prematurely. If you go that route use bricks for your curb. I would still prefer the cement board layer beneath, though.
Hey Roger, thanks for the reply, I finished the curb and am now stuck on the drain. The previous installer never installed a preslope so the bottom drain portion is level with the concrete subfloor and looks like a pretty corroded cast iron, I was going to start breaking up the concrete around it and was wondering if it is pretty standard to replace the p trap at the same time, or if the pipe looks good can I just cut off the old one and install a new one at the proper height? And one last question, I bought 4 mil plastic that I was going to put behind the CBU but am now wondering if I should just get the kerdi? I would only be doing the walls with the kerdi and not the pan, or is the 4 mil and the CBU a decent water barrier that would provide a long lasting shower? Thanks again for all the help!
Hey Justin,
I always replace the p-trap as well. If it is indeed cast iron it will eventually need to be replaced anyway and I would always rather do that while I have the access without needing to tear out a tiled floor to do it. Not saying it will need it within the next couple of years, just saying it may need it. You can always cut the old drain out and just replace it but I always replace the p-trap as well.
The 4 mil plastic with the cement board is a perfectly acceptable water barrier for your shower. That said (typed) let me say that the kerdi is more than acceptable – it’s just better. With the CBU the backerboard will get saturated with water eventually, the plastic prevents that from reaching your wall framing. Once saturated the CBU rarely ever fully dries out, the water is simply flushed through and replaced with fresh stuff every time you shower. This is completely normal.
With kerdi the waterproofing membrane is directly behind your tile. Any moisture that gets back there will immediately hit your waterproofing and be directed into the drain. Your shower completely dries out after each use – no standing water – ever. Topical waterproofing membranes are, in my opinion, absolutely the way to go. If you have a choice definitely go with kerdi.
If you do go with the CBU and plastic make sure your plastic overlaps the floor membrane so that any moisture running down the plastic is directed into the membrane and to the drain rather than behind it.
Hi, thanks for putting up all this great info. I am building my curb now and was going to do a curb/pony wall thats a couple feet high out of brick. do i need to stagger the bricks? and do i spread a thin layer of motar over the bricks and then cover with metal screen and then another layer of mortar? im just not sure what i need to do to the pony wall to be able to tile it, and how shold i attach the screen to the brick? also should i attach the liner to the inside of the pony wall with anyghing? thanks for all the help!
Hey Justin,
The problem with your plan is that your liner will need to run up that brick wall a minimum of three inches above the top of your curb. You will then need some type of backerboard or substrate on which to attach the tile. I think the best thing to do would be to either build your pony wall with studs and backerboard and install your liner as usual behind the backerboard, or use a bonded (topical) membrane as your waterproofing for your shower floor and up that wall. These are products such as Kerdi or other sheet membranes, or liquid membranes like hydroban or Redgard.
The issue is not being able to run your waterproofing membrane from your shower floor up behind your tile substrate. Building your pony wall out of brick does not allow any way to attach the rubber membrane to the brick solidly enough to attach tile (or anything else) in front of it. With a topical membrane you can build it out of bricks, float it out smooth with thinset, then waterproof everything. Any topical waterproofing allows for tile to be attached directly to it.
And yes, you do want to stagger the bricks to solidify the wall. Stacking straight without staggering leaves every straight joint as a weak link. If you stagger them it will lock them all in to one solid structure rather than several ‘stacks’ of individual bricks.
hi roger, nice to find some one that calls a jerk a jerk. I have always done my own remodeling and repairs and over the years have seen nothing but misinformation and crappy work. After remodeling our hall bath I decided to do our master bath which contained the standard sheetrock shower of the 1970’s. Neo angle and no two walls the same dimension, Ceramic floor with a lead pan that was installed so out of square that 11″ went up one wall while 3″ on adjacent wall plus the liner was torn and some kind of rubber ball was shoved in the corner with caulk.
I got lucky as it did not leak but curb was destroyed, as it was studs wrapped in sheet rock, My question is the clamping drain I am using has beveled edge for recessed apps so it only sits about a quarter inch of plywood. Should I raise it in order to get a thicker preslope by the drain. I was going to have a (tile guy) do this work but he stated pre slopes are not needed. that is what the liner is for, After tearing out the lead liner i could see that water had been standing in there for years. So here I go again trying to do it right the first time all I need is good info, thank you, joe
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Hey Joe,
I was wondering what the hell I did with that rubber ball.
I would raise that drain. 1/4″ isn’t that much for the pre-slope to hold together. If it is that thin it will break off fairly easily and I wouldn’t trust that around the drain. Easier now than later.
Sounds like you had one of them ‘custom’ showers built.
Roger, thanks for the quick reply. i downloaded the installation instructions for the souix chief 821 drain i am using and sure enough it shows about 1/4 inch of primary mud under the flange.i have some 1/4 hardibacker board scraps, should i try to make some round shims out of these for under the drain? also do i need some kind of pvc corners for the curb cuts?Never done one before,Any different for neo angle? thanks again ,joe
Hey Joe,
You should be able to use the 1/4″ hardi for drain shims. You can use dam corners on the inside of the curb where it meets the wall.
The neo angle showers are different with the curbs. On the outside corners you cannot get pre-made corners to fit, you need to just make sure you have them cut carefully and a patch placed over the exposed area with a 2″ overlap and the proper glue type for your liner. Do not cut and glue the liner inside the pan, only from the inside top of the curb at the angle toward the outside of the curb. Everything from the top of the curb down inside the shower should remain one piece and all cuts made above the top of the curb.
First timer! Completed my pre-slope; 2 bags of sand topping mix and 1 bag of sand. Added just enough water to stay form together when squeezed in hand but broke apart very easily when push down with one finger on form ball. Beat down with wood float and smooth surface with metal towel. Slope of 1/4″/ft. 1/2″ at drain PROBLEM: After letting dry for about 30 hrs., I decide to sweep off with nylon hand broom. The surface and easily sweep away and if I keep sweeping, I could all the way to subfloor! Is this normal/ What did I do wrong?
Hey Greg,
There are two reasons it may be doing this. It may be either one or a combination of both. The first is that you did not get enough water mixed into your mud or it was not mixed consistently enough. More likely you did not get enough, mixing it inconsistently is immediately noticeable. The second cause may be that you did not pound it down hard enough. You really want to beat the crap out of it.
You know, like the last DMV employee you spoke with. You want to make that mud deck as dense as possible.
If I had to guess I would say a bit of both but more of the second. Another problem is that you are sweeping it – don’t sweep it. It is supposed to be sandy – really. If you have too many loose particles on top that simply is a sign that you did not pack it well enough. If it is good and solid (short of the ‘sandy’ factor) you can just mix up some thinset and coat the top to give yourself a workable surface. If you absolutely need to clean off some of the top use a shop vac but do not hold the nozzle against the mud deck itself, only about a 1/2″ above it. Holding the hose against it will suck a hole right out of your floor. Sandy is normal. If you cannot poke your finger through it then you did it correctly and it’s fine.
Hi Roger, I love love love your site! It’s so good to meet a floor geek
I have a question about PVC pipe. I ripped out a fiberglass shower stall and found, roughly a 2’ x 2’ hole in the corner of the sub-floor where they laid the pipe. This is an old 1800’s farm house. The plumbing was put in sometime in the earlier 20th century – I guess. To reinforce the sub-floor I put in 2×6 joists and then placed ¾” plywood over the entire space of the shower stall – 3’x4’. When I went to place the 3 piece drain assembly I was short the ¾” distance to make the connection. To remedy this I wedged a 3” block under the pipe which raised the P-trap pipe up far enough the reach the drain connection. The connection fits in the 1” inside size fitting for most of the opening. However, there is about a quarter the pipe on the lower end where it only goes in about 1/4 “ give or take a sixtieth. My question is, is this okay? Should I put silicone along the end to be safe? I did use cement and it is good and tight. Or, do you think that I should extend the P-trap pipe? If so, what’s the best way to do this?
Thanks for your help! Jenn
Hi Jenn,
The reason it is doing that (and I’m sure you already know it) is that when you wedged the block beneath the p-trap it tweaked the vertical coupling pipe sideways a bit – strangely enough about 3/4″.
It may be ok, but I wouldn’t chance it. When dealing with water think grand canyon – water carved it. That means your dining room table below that shower doesn’t stand a chance.
Silicone is effective only to keep water out, not to keep water in. In keeping water out of a space such as a corner of a tub, it does not require any strain on the adherence of the silicone to the substrate, that is to say that it does not try to pull or push the silicone away from whatever it is attached to. If you attempt to use silicone around your drain it will constantly push that bead away from the pipe due to the pressure of the water. It won’t last any significant amount of time.
While the coupling may ‘feel’ like it is good and solid it is actually not. For a solid connection you need the entire 1″ of pipe contacting a full 1″ of pipe. By tweaking it sideways your pipe is only actually contacted in a small ring probably about 1/4″ wide all the way around. Think of a smaller pipe inside a larger pipe. If you contact the smaller pipe on one side at the opening the upper half of that side will not be in contact with the larger pipe. The upper half of the opposite side will be but the bottom of that side will not be. Knowwhatimean? Probably not. I have a way of confusing things.
The absolute best thing to do is go get a coupling and lengthen that p-trap pipe. They make couplings to extend your drain pipe. It would be a hell of a lot easier to buy and install a $2.00 piece of plastic now than replace a $1000 shower floor and whatever structural damage it may cause. if you cannot find a coupling short enough just get the shortest you can find and just cut the vertical p-trap pipe to whatever size makes it fit.
Absolutely well done on ensuring the stability and reinforcement of your subfloor! Don’t let a piece of plastic ruin all your hard work.
Roger <– Certified floor geek.
I am doing a bathroom job and before reading your write ups I have been putting the corriloyd/membrane down first and then the mud on to with cement board on the walls so far all the jobs have come out great and are still going. Should I use welded wire mesh on top of the membrane or just leave it out so the membrane doesn’t get sliced?
Hey Mickey,
Never place welded wire mesh anywhere against your membrane except around the curb. Even then you must be super careful not to puncture your membrane.
Are you putting a pre-slope down? If not you need to start doing that. A traditional mud bed will retain moisture from the shower’s regular use and will be flushed through regularly with each shower. That’s completely normal.
However, if there is no pre-slope and the liner is flat on the floor the mud bed can only flush out water which sets above the drain. Any water level with or below the weep holes will never be replaced and will simply set stagnant.
With a pre-slope the entire area of the mud be which gets saturated is above the weep holes and will be flushed through regularly.
Thanks for posting all this great information. We are first time shower installers and have been using word-of-mouth adivce from a variety of sources (including the Home Depot / Lowe’s staffers), but things were really not clear until we read your stuff. We have made some adjustments to our materials list and are finally ready to get started. Thanks…I am sure you saved our project!
Glad I could help, Russ. If you have any questions please don’t hesitate to ask.