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
Roger, I hope you can clear up some questions I have concerning the pre-slope. My 3pc drain sits right on top of my concrete basement floor. Leaving me with about a 1/4″ from the top of the floor to the top of the drain body. Is a 1/4″ sufficient? You recommend it being atleast 3/4″ thick. Also, My shower is 44″x44″ giving me roughly a 1/2″ pitch towards the drain. Can you go more? If my math is correct my 1/2″ pitch plus the 1/4″ at the drain body will give me a total of 3/4″ at the outer perimeter of the shower base. Will that be thick enough? Also, there are a lot of formulas for mixing deck mud. I’m far from being a chemist, but I highly doubt that I need a 60lb bag of the quickrete sand and topping mix. Can I measure by using trowel amounts. Meaning 1 trowel Portland 5 trowels sand?
I just wanted to also say that before I read this article I was going to buy the quick pitch system that’s available on the internet. Roughly about $200 dollars. After reading your instructions I believe its a waste of money. Thank You for taking the time to right this step by step guide.
Hi Paul,
Yes, 1/4″ is sufficient at the drain for the preslope. Yes, 3/4″ at the perimeter is sufficient. Yes, you can go more if you want.
Yes, as long as you have one part cement to 5 parts sand it matters not how you arrive there. One grain of sand at a time if you want.
THANK YOU
Hello Roger Mr Floor Elf! i found this thread and fromt he onset it looks like it will help with my project. Unfortunatley i am not starting from scratch to build a shower floor. I am trying redo or fix what i currently have as a shower floor. I wanted to know if i could just trace back your steps to a point where it makes sense for me to start or if there are different steps for an existing shower where the floor is crubmling beneath me! i am no way an expert but am pretty handy and follow direction well. I am doing it on my own as i found the quotes for the job to be obnixious to say the least.
the project:
bought a house preconstruction with a free standing shower in the corner of the ensuite bathroom. three sided curb base with glass walls and a glass door. floor was uneven when i moved in so i had them fix that deficiency… 7 years later it now it looks like it was fixed by my four year old. floor is as even as a mogul hill on a ski slope! flor tiles are popping up and the grout is breaking off in bits and the tiles on the inner wall of the curb are falling and cracking and as suck it is now leaking! I was thinking i just remove the tiles …floor and inner wall of the curbed base.. hammer away and even out the bumpy base and then add some thinset and new tiles. is this the appropriate action? or do i get rid of it all base and tiles (leave the curb) and start anew?
Please help!
Peter
Hi Peter,
What you need to be concerned with is the floor liner, which is under the mud deck, and the way it is wrapped over the curb. If it’s leaking that will need to be replaced, so you need to get down to at least that far. It would also be my be that there is no preslope beneath your liner, so once you remove the liner you’ve essentially removed the entire floor – so there you go.
Thanks! now if i find that the liner is intack then just redo the mud deck and go? What if it is leaking …. i would rather not have to take any tile from the wall sides (as opposed to the curb sides)… it would be under there as well no?
As long as it is in good shape yes, just replace the mud deck. If you do need to replace it you’ll likely need to remove at least a foot of the bottom of the wall. The liner needs to go up three inches above the finished height of the curb.
OK, couple of questions: 1.can you give some more info about putting the pea gravel around the weep holes? How much do you use, does the dry pack just stop at the edge of the drain and there’s 3/4″ of pea gravel?
And then 2. Do I really have to go back out and get a bag of sand to add to the quickcrete?
Thanks so much for your help–yours is the best, most clear info on all this!
HI Jeri,
1. You only need as much pea gravel as will fit in the palm of your hand on top of each weep hole in your drain. It is there to keep deck mud out of the weep holes, that’s all. Just enough to cover them.
2. Yes. Absolutely. Straight quickrete will crack when it cures at that thickness.
Roger, thanks for the great resource!
I am a first time remodeler, so pardon my ignorance. I think I may not have done it right thus far, and would appreciate a little direction. The plumber cut out the old drain below the slab, and I glued in a 3-piece drain. There was a little space below the new drain (no more than 2″ in any direction), but the edges of the drain rest partly on the slab. I spread some thinset on the slab but didn’t read posts about using a notched trowel until later. I spread it about 1/8″ all over. I tamped down a pre-slope like you describe. However, my main concern is about the drain. I’d rather back up now, if needed, than wonder later if I did it alright.
1) I poured a lot of water down the drain after gluing the flange on, and no water seeped out the sides, but the pipe never seemed to fill up all the way. Is there a way I can be certain that I glued it adequately?
2) Should I knock out some of the pre-slope and try to fill in the space below the drain with regular concrete mix, or is the space small enough that I don’t need to?
3) Because the bottom flange of the drain rests right on the slab, I wasn’t able to put deck mud underneath the edges. I sloped from the shower edges to the flange, finishing at about 1/4″ thick. I know it really should be 1/2″. Should I just start over, extend the pipe up more and put in a new drain, or can I make it work at that level?
4) I was going to use Redguard. If the drain and pre-slope will work the way they are, then i think this is my next step: Put pea gravel around the weep holes, put down a little more thinset, and add mud deck to make a total of 1 1/4″ deck, with redguard over the top. Is that right?
5) I built a curb out of bricks, but it’s not quite straight and bows out 1/8″ in the center. I’d like to square up the curb with the drywall on the wall adjacent with the shower. Can I do this using durock and some thinset that is thinner in the middle than on the edges?
Thanks,
Liz
Hi Liz,
1. Seems to me if the pipe never filled all the way up then it’s working just fine.
It’s fine the way it is.
2. If the drain is solid then no, leave it the way it is. If it moves at all then yes.
3. It’s fine
4. NO. The mud deck needs to slope down to the weep holes. They weep holes need to remain operational which means the waterproofing layer needs to to run down below the weep holes.
5. Yes, but deck mud would work better.
Thanks for the immediate response!
If I understand correctly, I should redguard over the preslope and finished curb, then add a final slope over the RG.
Step 3 of the shower pan instructions suggests plugging the drain and filling the pan prior to proceeding. Would you recommend this with the RG as well?
Hi Liz,
While you can do it that way it’s fairly counterproductive to have a topical membrane then cover it with mud. You can install tile directly to the redgard. Yes, you should do a flood test.
Hey Roger,
Thank you so much for taking the time to point all of us lost sheep in the right direction. This is by far the most informative site on the net.
I am in the process of building a roughly 3′ x 4′ shower. All of the durock is hung, corners, seams, taped and mudded (thin set) along with the screw holes. I am now at the point of making the shower pan. I am planing to use hydro ban for my water proofing so I purchased the Laticrete bonding flange center drain. I dont consider myself to be very handy mostly because Im not. So my question is … When following your instructions as far as figuring your slope then marking the walls following that with a perimeter of deck mud at that height. Can I do the same around the drain as well then let them set up over night or does it all need to done at the same time? My thoughts are that it would be much harder for me to goof things up if I have essentially a cement to cement screed.
My major concern is the drain not remaining level and moving around.
If you walk me though that obstacle that would be GREATLY appreciated.
Thanks Again
Jamie
Hi Jamie,
It is normally best to do it all at the same time. Set your screeds around the perimeter, then install your drain and pack mud under it. Then fill in the areas between the perimeter and drain and screed it all flat. If you pack the mud under the drain nice and tight it won’t move anywhere. As long as you keep your level handy you can ensure it remains level. You can always tweak it if you need to as you screed the base.
Thanks Roger. I will give it a shot. I have one more quick question. When putting the durrock on the walls I alslo wrapped the 2×4’s that I had in place for curb. Is this an acceptable practice since I will be using hydro ban? I did this because I have framed a door opening rather than starting the curb at a perpendicular wall. Essentially I have a door opening within the wall. I was not sure that I would be able to build out the thickness on the curb to match the thickness of the durrock. Is that okay or should I wrap the 2x’s with the tar paper and lath, then mud?
Wrapping the curb is fine since the waterproofing is over the face of what you’ve built.
Wow, thanks for the quick reply! That makes more sense now.
I’m confused on the need for bricks being used for the curb on a concrete slab. Why is it ok to have shower walls made of studs on the floor with a wood plate, but not ok to have a shower curb with wood?
Hi Walt,
Because the baseplate of a wall will expand and contract a lot as well, but it isn’t covered on all sides and sealed in with tile. If there is any movement in the substrate of tile your grout will crack, and your tile may. When a baseplate moves it will push the studs in the wall up a little, vertical movement in the wall cavity doesn’t affect your tile at all. Vertical movement in a wooden curb cracks stuff.
As if this process wasn’t complex enough…
First off, thanks for all of the informative and thorough shower floor info. I see a lot of elements that people often overlook.
My plummer is going to be running Radiant water pipes underneath the entire bathroom floor within the mud there. He said, why not just do the shower as well. I was planning on taking him up on the offer but I’m wondering if that will add any additional complexity to the project?
My assumption is that the line would be buried in the mud that slopes down toward the drain under the shower liner (or perhaps Fiberglass barrier if we go that route). Is that the case? Are there any gotchas or should I nix this offer ocmpletely rather than do something I’ll regret later?
Thanks.
Hey Ken,
You can do that without any problems. The pre-slope will just be thicker, enough to compensate for the heat.
I put down 3/4″ plywood on top of the existing flooring. Am I dreaming or did I read on your site someplace (which I can’t find) to NOT screw the plywood into the floor joists, but just into the original flooring?
That is correct. I’m sure it’s in a comment somewhere (at least a couple of them). Feel free to search all 21,286 of them to see if you can find it. That is, you know, if you have a lot of time on your hands.
I am in the middle of a bathroom remodel and was wondering if my contractor made a mistake by not putting down a membrane, liner or a water sealer on the exsisting concrete floor for the shower. It was too large of an area for a shower pan. He did however pour some thinset on it before he put the tile on. I am worried about leaking. Thanks for your help.
Hi Scott,
Yes. Mistake is not how I would describe it, if what you are saying is accurate a major screw-up is more descriptive. The shower floor NEEDS a waterproofing of some sort. When you say ‘too large of an area for a shower pan’ do you mean a pre-fabricated shower pan? Because there is no such thing as too large an area to BUILD a shower pan. I don’t know why he would ‘pour thinset’ on it, that will do nothing but make a damn mess. I have absolutely no idea what he has going on there.
I have an Oatey drain, but it really only allows for a preslope of 3/8″. Should I be looking for one that is taller to get closer to the 3/4″. Thanks
The 3/8″ works fine.
Roger-
Thanks so much for the wealth of information that you are willing to share. You really seem to have the most complete website / info out there on these subjects. Damn funny too.
So….the question. I’m doing a “traditional” shower floor with a deck mud preslope. This is round 2 on the preslope for me (joy joy!) First one seemed to turn out very good using “pre-pitch sticks” until I put a level on it. All good except for one quadrant where the subfloor sloped away (I checked level in many spots but missed this corner apparently). So I got practice using a sledgehammer in my master bathroom. Yay!
On this round…diamond lath on 15# felt on 3/4″ + 1/2″ plywood (with 2×8’s 16″ OC). Lost the pre-pitch sticks this time and followed your method. To compensate in the low corner I essentially made a level line around the perimeter so this corner’s deck mud is thicker. Mixed deck mud at about 4.357:1 (give or take!
) and beat the crap out of it with 2×4’s and magnesium float (at least I thought I did).
Floor turned out pretty much fine- no slope issues as in the first round. Water should make its way to the drain swimmingly. It has been curing 24 hours so I thought I’d walk on it for fun. This time seems fine except for one spot about the size of my right foot. Sigh. There is a bit of a click in this spot one I put all my weight on one foot. It seems like perhaps the mud didn’t quite penetrate the lath here or the lath came unstapled and is supporting a portion of the mud. Really can’t feel any flex at all, just the subtle click with all weight on one foot. This area is about halfway between drain and corner…mud prolly close to 1″ thick here.
My wife thinks I am being anal to even worry about it….I hope she’s right cause I really have had enough fun making 2 pre-slopes. So, am I crazy? Do I proceed with my liner, setting bed etc or redo again and hope I don’t botch something else?
Thanks for any words of wisdom! Paul
Hi Paul,
You can just leave it if you want to. It’s not going to make any difference once the liner and top bed are on it. If you must fix it first (OCD – I completely understand…) drill a 1/2″ hole through your mud down to the lath and fill it with more deck mud or thinset.
Great! Thanks so much! Paul
OK i just beat the hell out of the deck mud
next i will put up the cement hardy backer-board, then i will use white seem tape on the seems and regard everything to the ceiling three times to make sure it is all waterproofed good this will also include the curb made out of bricks. then i will tile. yes!!!!???? 
Hey Dan,
Yes. As long as by ‘white seem tape’ you mean alkali-resistant fiberglass mesh tape.
No snarky or brilliant remark just a plain ol’ thank you for your well written sound advice.
It is rather strange that many (most) of the web sites I checked befor finding you do not speak of a pre-slope. They of course all speak of sloping the floor but speak of laying the water proofing membrane directly on the substrate. That just didn’t seem logical.
Again, thank you.
Don B.
ok i just got my studs straight and in place ; i have a perfectly leveled cement floor and my plumber moved the drain into the center of the floor and that has been patched. so now i put on 6mls of plastic on the studs put in my harder backer and redgard the walls and floor? then i put thin-set on the cement floor put in place the deck mud (pre-slope let cure. then redgard this and place in the final slope of deck mud right?
Hi Dan,
Not quite. You don’t want the barrier behind the substrate if you’re using redgard, and you don’t want it under your mud deck either.
Place your deck mud over a layer of (wet) thinset on your concrete, let it cure, put your hardi on the walls, then redgard it all. You’re working way too hard.
You can do a pre-slope, use the redgard as your liner, then another mud deck, but it negates the use of a topical membrane. Just do one mud deck and then install your redgard over everything and tile right to it.
Roger,
Thank you for all the detailed info, and the wit and humor. I will attempt a shower floor now. After spending all morning reading and watching youtubes, the internet is a cesspool of conflicting info but youve got a consistant method to your madness here.
So…. ive got all this sand topping piled up here, extra sand to bring it to 5:1, a clampring drain, im framed, substrated, ready to poke a hole in floor for drain.
but…..looking at your cross section of drain thru floor it conflicts with the sioux chief and oatey install images. Your image is logical in that it shows a large enough gap tween the flange and substrate to be able to get some thickness of mud under it. the factory cutsheets show bottom of flange screwed right against tar paper on the plywood. the sioux chief drain i have here if screwed down like they show will have a half inch from edge of flange to the substrate. that seems too thin for the interface of my pre slope mud to the flange. wont this thin mud edge crumble and crack?
should i raise (shims or spacer) this drain flange up before i screw it to substrate and pack the pre slope? does it matter at all since i will be putting the liner over it , bolting the lock ring down, and packing another layer of mud down on all of it?
Hey Tim,
You can actually do it either way with the traditional liner method. *Technically* you should have a minimum of 3/4″ deck mud at the drain, that is the thinnest layer of deck mud which has been tested to be stable. However, with a pre-slope it doesn’t really receive direct pressure, so it’s normally just fine. Even if it does crack a bit under the pre-slope it won’t affect anything since nothing is directly bonded to it.
Dealer’s choice, I’ve done it both ways without problem. I *prefer* the 3/4″ minimum, but I know that doesn’t always work out. You can do your deck by doing the back of it first then moving out to do the front. Do it all at once, but every portion doesn’t need to be done all at once.
The person building our shower installed a schulter floor and now he is tiling the floor but he is shaving the tiles sloping to the drain very thin because the drain is 1/4″ below tile, is this normal and won’t the tiles break being so thin?
Hi Gloria,
It’s not ‘normal’, but it’s definitely a viable option. When presented with problems we do what we need to make the installation work, and work correctly. The end product is what you should be concerned with, and you are!
Provided the tile is installed correctly then no, there won’t be any problem at all with the tile cracking.
Dear Roger: my interior wall is crooked and bows in and out i am attempting to put cardboard shims on the face of these 2×6 and square them against a cement wall my end of the shower. How square do these walls have to be in order to get a good end result? Have to fix the otherside is the kitchen what do i do?
Hey Dan,
Just get it as square as you can. The only type of installation it is absolutely necessary to get perfectly square is an installation on-point (diagonally). Any straight installation can be compensated for so it won’t be noticeable.
Roger: My plumber replaced galvanized vertical pipe with pvc pipe running from the kitchen through the side wall of my bathroom. The 2×6 and floor plate in the shower were so rotted i had to tear out the floor plate and amputate about 3 ft of 2×6 from the floor upward in order to get good wood. In order for me too scab a 2×6 from the floor plate upward it only leaves about an inch of wood because my brilliant plumber used 3 inch pvc between the wall. So could i use a 2×6 plate with red heads for the flooring and use 4×8 sheets of treated plywood all the way up that wall in order to enclose the pipe and give my backer board a solid support?
Hey Dan,
You can provided you’re using a topical waterproofing membrane. If you plan on using a barrier behind your backer for waterproofing it won’t work, it’ll trap moisture.
Hi Roger,
I been nursing some pain for some time and avoid doing the shower floor for the past couple of months at least. Anyway I bought the Kerdi shower drain and once attached to the trap it sits one inch above the plywood.
I don’t have a choice here as the 2″ trap under the plywood sits almost on top of the dry wall ceiling below.
So my question to you, is it ok to add 1″ of drypack around the bottom of shower drain opening or do I go out and buy some plywood to fill the gap under the kerdi shower drain. I would like to up load some pictures but I’m not sure how. If you can tell me I will send the pictures that I took.
So I’m thinking I have two options
Buy another plywood to fit inside the shower floor roughly 3’x5′ cut the hold and then the kerdi drain will sit on this new plywood (so basically doubling up the plywood here) and then place the drypack on top. Question here does it have to be 1″ thick the plywood or can I get away with 3/4″ or 5/8″?
2nd choice is just place a few screws to hold the kerdi shower drain in place its apprx. 10″ round. And place apprx. 1″ of drypack all around under the drain and another 1/4-3/8″ of drypack on top of the kerdi shower drain when I’m doing the slope.
Sorry for the winded email but I don’t want to F__ this up especially after sitting on my ass for so long.
Thanks Tony Mazz
Hi Tony,
You can build up the deck mud to the 1″ height with absolutely no problem. I don’t know why you would be placing drypack on top of the kerdi drain, they are made so that the edge of the drain flange sits flush with the top of the mud deck.
I am wondering when laying the thinset down over the concrete floor prior to making the pre-slope what are we supposed to trowel it with..a particular size or just spread it flat on the concrete surface? We are using the pre-pitch and quick pitch kit to build the shower pans. with the pre-pitch you are supposed to adhere the float sticks to the concrete with double sided tape, it does not mention pouring any thinset on the concrete. Will this be a problem? Do we just lay the float sticks on top of the thin set ( we purchased Versabond for the thinset layer). Thanks for the help
Hi Barb,
You can use whatever size trowel you have, doesn’t make too much of a difference. The float sticks can be embedded into the thinset, the double-sided tape is just to hold them in place while you form your deck mud.
I am having a hard time finding tar paper. If I use 4mil plastic sheeting on the wood subfloor then lath, then concrete pre-slope then 40mil membrane, why isn’t a mold sandwich a concern here?
Thanks!
Because the plastic on the floor should not be sealed in any manner around the edges. It’s just there to prevent the substrate from sucking moisture out of the thinset, thus weakening it.
2 points for making me use the word ‘thus’!
Great site! I have novice questions. I have a second flood shower. I put down painter’s paper to separate the mud deck from the wooden floor. It’s supposed to work….according to a random person at Menards. I put in metal lath but instead of deck mud I built my pre-slope with Ultra-Flex 3 polymer thinset. First time using it. Very sticky. The floor is not totaly smooth. I was having a terrible time with the ultraflex sticking to the float. Also, I worked with that stuff for about 5 hours (great workout by the way). It is possible to get it too wet or to overwork it? What would be my next step to correct any mistakes I may have made at this point?
Hi Jody,
That is the completely wrong product for that application. Thinset of any type is used to bond tiles to the substrate, not to build a structural element in your shower, which the pre-slope is. It’s sticky because it’s made to bond stuff, not build stuff. You need to remove all of that and use deck mud. It is formulated specifically to withstand everything your shower floor needs to withstand, 1 1/2″ (or however thick) layer of thinset, ultra-flex or not, is not (and will not).
Also – painter’s paper? I’m assuming just paper that’s used to tape stuff off with? If so that will not work. You need tar paper down there. It’s not to separate the mud deck from the wooden floor, it’s to prevent the wood from sucking moisture out of the deck mud prematurely, which weakens it.
Due to being in an older house with semi-typical above ground floor drains (you know; step up to the toilet type house), the top of my lower drain piece sits 2 1/2″ above the concrete floor. No way to get it any lower (even the actual pipe is above the floor). I’ve been wracking my brain trying to figure out how to raise this floor.
Pouring a full 2 1/2″ thick floor for a 5′ square shower is 20+ bags, a lot of extra work and $ just to get it to height. Never mind what’s needed for pre-slope and top layer.
I’ve thought of raising the floor up with a false floor made simply of 2 x 4’s on 1′ centers and plywood, then doing the standard pre-slope with mesh & mud, etc. I could also do the pre-slope with the plywood so I only have to skim the slope with mesh and a thinner coat of mud.
Am I OK using 2 x 4’s (on tar paper) on the concrete floor? Should I be concerned about movement as the 2 x 4’s have no rigid mounting? Strips of plywood instead of 2 x 4’s? Small curbs and then place concrete board on top with mortar mix placed atop the curbs, and weights to keep it down while hardening. Going crazy thinking of too many ways to solve this (short of mixing 25 bags of shtuff just to get to height. Any other ideas?
Hi Grant,
The only way I would trust a wooden frame over concrete under a shower floor is with pt wood and tapconned into the concrete. (deck mud will compensate for movement of the pt wood, so no ‘don’t use pressure-treated’ rule here). Short of that I would mud it. A pain in the ass, but no other options I’m aware of for that scenario.
Hi,
Amazing knowledge and well written. Thank you.
I am building a shower floor on concrete. From your post “How to Create a Shower Floor – Part 1” – Section “Curb and Pre-slope” you wrote that there are two ways to do this.
1. A single-layer shower floor which can then be coated with RedGard or a similar product or covered with kerdi to waterproof it.
2. Shower floor with a liner which will have two layers – a preslope, the liner, then the top slope which is then tiled.
I would like to do point 1. A single layer of deck mud sloped with kerdi to waterproof it. Will this be water tight as method 2? What is the preferred/better method? Kerdi over curb instead of pvc membrane? Hurt to use pvc membrance first on concrete then deck mud and kirdy on deck mud?
Hope this is clear.
Thanks again,
Mark
Hi Mark,
Yes, it is waterproof as well as method 2. I prefer the kerdi, it’s cleaner, your substrate does not get any moisture and your shower dries out more quickly. Yes, kerdi over curb as well. Yes, it will hurt to use a membrane under a kerdi deck. You’ll be creating two different waterproof layers with concrete between them, from which vapor can not escape – it WILL grow mold. You want one or the other, never both.
Thank you Roger,
So should I use (option 1) a different drain than what would be used to sandwich the pvc membrane between the flanges? Or, should I use drain with flanges to sandwich the kirdi?
Here are my steps:
OPTION 1 – Drain with one flange only
0. Durock to floor
1. Place Drain
2. Thinset on concrete
3. Sloped Deck mud over thinset up to surface of flange
4. kerdi over Curb and Deck mud to top of flange
5. Screw on drain to height of tile.
6. Tile floor
OPTION 2 – Drain used to sandwich PVC membrane between flange
0. Durock to floor
1. Install lower flange drain to correct height on abs drain.
2. Thinset on concrete
3. Install Slopped Deck mud over thinset to top of lower flange
4. Install kirdi over curb and deck mud and top of lower flange.
5. Install top flange to lower flange with kirdi in between
6. Pee gravel around weep holes
7. Deck mud over kirdi to set finish drain height.
Since there is no PVC membrance behind the durock I am assuming I must kirdi the durcok walls as well for vapor and water penetration.
Thanks again for your cornacopia of knowledge. Very happy to see that you are sharing it with us mere mortals ; )
Mark
If you use kerdi you need to use a topical drain, that is the one with just a single flange.
If you have a concrete substrate under where your shower will be you do not use durock on it. Ever. The deck goes directly to the concrete. A topical drain does not have a ‘screw on’ drain – it is a completely different drain. You CAN NOT use a regular drain with a kerdi shower floor.