Well, you’ve made it to the final step. If you have arrived at this portion of the instructions without first reading the rest, start with How to Create a Shower Floor. Go ahead, I’ll be right here when you get back. I’ll just sit back and drink this beer Pepsi while I wait.
Okay, now that we’ve ensured that your shower liner is indeed waterproof and won’t leak into your dining room and carve the Grand Canyon into your basement we’re ready for the final portion. The top mud bed is the surface onto which your shower floor tile is actually installed.
What we will now be doing is fabricating your top mud bed directly over the top of your waterproof liner. The top bed will be 1 1/4″ to 1 1/2″ thick – consistent throughout from the drain to the wall. Since you have a pre-slope beneath your liner (umm, you DO have a pre-slope beneath your liner, right?) you already have the correct slope for drainage. By making a consistent mudbed for your top slope it will follow the slope for the same amount. Know what I mean?
Here, take a look at this badly created diagram and that may help explain it – and don’t give me any crap about my lack of photoshop skills! You can click on the diagram for the full-size version.

The top mud bed is what we have left for your shower provided you’ve followed in order. See how the top mud bed is properly sloped toward the drain even though it is a consistent thickness? That’s what I mean.
A couple of notes before we start making a mess. You can install your moisture barrier and backerboard on the walls at this point if you want to. DO NOT put any screws through the liner, stop them above the top of the liner. The top mud bed will hold the bottom in place if you choose to do it like this. Your moisture barrier must go over the top of your pan liner as in the diagram. This ensures that any moisture will run down into the shower rather than into your framing behind your wall.
In my wonderful diagram I have the wall substrate or backerboard installed after the top mud bed is fabricated, you can also do it in this manner. Installing it before, though, assists in getting a level perimeter around the base of your shower since you can draw lines on the wall. It’s up to you.
Determining the thickness of your top mud bed relies mostly upon the amount of vertical movement you have in your drain. You need to make sure that you can unscrew the center portion (this moves the top of the drain up) enough to be level or a hair below the top of your mudbed with tile. The easiest way to determine this is to start at 1 1/4″ – that’s just the thickness I prefer to have if possible.



You need to place pea gravel, spacers, or something similar around the drain where the weep holes are located. This prevents deck mud from clogging up your weep holes and nullifying all of your hard work. If plugged up the shower cannot properly drain beneath your floor tile and your house will fall down and your dog will burst into flames. Okay, maybe your house won’t collapse, but it won’t be a good thing. Make sure you place something there that prevents clogging of your weep holes.
Place a piece of your floor tile on the base of the drain – on the upper part of the flange – and unscrew the barrel of the drain until you reach 1 1/4 inch. As long as the barrel is still firmly screwed into the flange at this height you have enough to create a 1 1/4″ top mud bed. If the drain falls out before you reach 1 1/4″ (it won’t) – go with 1″.


Now the fun part – we’re gonna make your lines so you can see what your doing, where you need to be, and make your slope correct and consistent. Get your 2 x 4 (which is actually 3 1/2″ x 1 1/2″ – economy I guess) and set it on top of your drain (Figure 1). Measure from the liner to the top of the 2 x 4. In this photo it is (or close enough to) 4 3/4″.
You then need to make that mark at the same height all the way around the perimeter of your shower walls (figure 2). If you have installed your backerboard you can just make that mark on the wall at a height of 4 3/4″. I use a laser because I’m a big Star Wars fan and that’s how I roll. Get one, they’re great for building showers and annoying small animals. That’s a versatile tool right there!
This may look a bit confusing at first, the 2 x 4 and all, but it will make sense shortly. Or not . . .
Now we need to prepare some more deck mud. Get out your shovel and mixing box. If you need the recipe again it’s here: How to Make Deck Mud. Start with the perimeter of the shower and dump your mud in there. I always start along the back wall of the shower.



Get a good amount of deck mud packed along the walls higher than where you want it to be. Once you have a good amount packed against the wall grab your 2 x 4 and place it flat against the wall. Get your hammer and beat the deck mud down with the 2 x 4 until the top of the 2 x 4 is level with the line you’ve made on the wall or your laser line (figures 3, 4, and 5).
Simply continue to do this around the entire outside perimeter of your shower keeping all the edges level with your line. By utilizing the 2 x 4 with the laser or the drawn line you can be certain that the floor is level all the way around (Figure 6).
Some people have asked me why I have a hole in one of my 2 x 4’s. It’s a very detailed explanation – ready, pay attention – so I can hang it on a nail when I’m not using it. That’s all, stop overthinking everything, it’s a hole in a 2 x 4. You don’t need a hole in your 2 x 4 unless you have a storage problem.
In the next post we’ll finish up your floor, fill in the center and get ready for tile!
Hey Roger, thanks for the blog – it is great. I just wanted to clarify the numbers for a traditionally waterproofed floor. My shower is smaller and my pitch will be 0.5″ from wall stud to drain perimeter. Do these approximate theoretical numbers look OK? I apologize for getting down to sixteenths of an inch – this is really a theoretical question to make sure my thought process is correct. Thanks for your feedback.
Assume Top of Tarpaper on subloor height is 0″
Add pre-slope (metal lathe does not add any height)
Top of pre-slope @ drain perimeter = 3/4″
Top of pre-slope at wall studs = 1 1/4″
Add 1/16″ for liner thickness
Top of liner at drain perimeter = 13/16″
Top of liner at wall studs = 1 5/16″
Add 1″ for top bed thickness
Top of top bed at drain perimeter = 1 13/16″
Top of top bed at backerboard/liner = 2 5/16″
Add ~3/8″ for 1/4″ thick tile + thinset using 3/16×5/32″ trowel
Top of tile at drain perimeter = 2 3/16″
Top of tile at backerboard/liner = 2 11/16″
What would you do different in this case?
Hi Gary,
Those numbers are correct. The only thing I would do differently is have a beer and stop overthinking it.
Hi Roger,
I’m about to lay the final deck mud when I noticed a small pin hole in the pan liner. Its hard to tell if its all the way through but I’m pretty certain it is. This must have happened when I was hanging the hardiebacker. I was really careful (no shoes, nothing sharp around and put a couple towels down) but somehow it has this puncture. It passed the 24hr leak test before so I know it just showed up recently.
Starting over means tearing down the hardie, vapor barrier, and doing the liner all over.
Can I place some Redguard over the area? Or do a patch with left over PVC liner scraps? If I go the patch route am I correct in assuming a 2″ by 2″ square or 2″ diameter circle piece will suffice. The glue says overlap by 2 inches so…
It looks like a ball point pin stabbed it. Very tiny spot
THANKS!
Hey Ross,
Stop putting holes in your liner.
Patch it with a four inch square or circle (you should have two inches from the outside edge of the patch to the penetration – hence four inches).
Roger,
First off – thanks for all the information on the website, it’s been great! Now for my question: I just finished the second mud deck on top of the liner and it has cured. I have a consistent slope into the drain. As I look at where the mud deck meets the wall, the corners are 1/8-1/4″ higher than the middle because they are further away from the drain. I have not put the wall board up and I’m worried about the additional gap in the middle. Should I add more deck mud in the middle against the wall to eliminate the gap, plan to cut the first row of tiles to different heights, or is there something else you would recommend? Thanks!
Hi Mike,
You should actually have a level perimeter on the shower floor. Regardless, you don’t need to do anything with that if you cut the first row to different heights. If you want to level it out – sand down the base, not build it up unless you are adding 3/4″ or more.
Thank you Roger
Hi Roger, thanks to answer so I will use brick for curb but I want to put Kerdi on top of a brick curb, is that ok? When I join the bricks use the mortar after that I have tu cover them in a light coat of tinset or not before to apply the Kerdi membrane?
Yes, you can put kerdi right over the brick. You don’t have to cover them with thinset until you install your kerdi.
Hi again when you are available to give me an answer this is another question, for walls i used dens shield do i still need to water proof them?Thanks
Hi Marcel,
No you do not need to waterproof over densshield.
Hi Roger thanks to answer it, i have a concrete floor in my basement, so what is the easy way to build a shower curb? i want to use 2 by 4 than cover with liner than a layer of cement board. Acording you, wood is not that good on concrete even if a use that foam rool to protect the wood. Anyway what about the cement board to cover up the wood curb if i can use wood?or if i use bricks how i deal with membrane? you know let me know a right way to do it and i wil follow you> Thanks
Use bricks. Once they are thinsetted to the concrete wrap your liner over it, then metal lath folded in a ‘U’ shape to hold your liner in place. Then install wet mud (1 part cement, 4 parts sand, 1/2 part lime) over the lath to form your curb. The tile is bonded directly to the cured mud.
so if i use bricks for my curb in the end how i will finish with tiles? Thanks
Hi Marcel,
It depends on how you are waterproofing your floor. If it is a traditional floor you wrap the liner around it, wrap lath around it then form your curb with wet mud. Tile is installed directly to that.
Hi, tell me please the grout is water proff
Hi Marcel,
I would but I’d be lying to you.
Hey Roger,
Is there a method that you favor over the other when you hang the backer board wall i.e. doing it after final deck mud or before final deck mud? Is there a water drainage advantage to hanging it after deck mud? Doing it BEFORE seems easier because like you said it makes marking the final bed layer easier. But, hanging AFTER will leave a 1/8″ void (right) at the bottom because I should not rest it on deck mud to allow wall movement. What does one do about that gap, silicon the deep part then grout to tile depth?
In short, I’m trying to ask if there is a more professional and waterproof/drainage method, which method is it?
Thanks for your advice>
Hey Ross,
Every professional has their own method. I prefer to place it before the final mud deck. If you put it on after you don’t need to do anything with that gap, just leave it.
I’m doing my floor and walls all with Redgard, which is supposed to be able to have tile directly adhered to it. Is there a way that I could skip the top layer of deck mud, and just lay tile directly on the pre-slope painted with Redgard, as long as it’s flat? Or would I not be able to properly ‘space’ around the weep holes for drainage?
And at what point do I ‘screw in’ the drain for good? After the tile is all in, or?
Thank you for your wonderful tutorials.
Hi Brian,
You can provided it sits high enough that you can get your drain screwed down to be even with the top of the tiles. You need to paint the redgard down to tie into the weep holes. The drain should be screwed in flush as you are installing your tile so the thinset cures around it and under the tile at the same time.
Great information! It has really made sense of things for me. However, I am afraid my dog is about to burst into flames. I am considering changing plans mid stream.
My original plan was to use a liner on the floor and Redgard on the walls as I have a corner bench and shelf. I installed the drain and poured the pre-slope. Everything looks great. Unfortunately, I underestimated the difficulty of laying the liner on my irregularly shaped floor.
I’m beginning to think it may be easier to forgo the liner, poor the top mud bed, and Redgard the floor. My questions:
1) any problems with pouring the top mud bed directly over the pre-slope? I don’t imagine so, but thought I should ask.
2) what do I do about the drain which is already imbedded in the pre-slope? My thoughts are to apply silicone and attach the upper flange to the lower, pour the top mud bed shaping it around the barrel, then Redgard the floor down to the flange buried under the top mud bed. Will this work? What do I do about the weep holes? If this doesn’t work, how do I fire proof my dog?
3) am I missing anything?
Thank you!
Hey Mark,
1. No problem at all.

2. It’s kind of the right method. Google ‘shower floor divot’ and you’ll find the proper method of using topical liquids with a regular drain. Or order my liquid topical manual – it’s in there too.
3. I have no idea. Not with any of the questions you’ve asked.
I have my pan liner all placed and my mesh over my shower curb. I am going to be using a topical waterproofing membrane for my walls. Is there a problem placing your wall substate on the wall prior to your top coat when you are using a topical membrane for the walls? I feel like it would be easier to keep the top coat level, I just don’t want my dog to start on fire.
Hi Jon,
No problem at all.
First thank you for all the info on doing this for us weekend DIY folks.
I have a few questions though first is about the curb have pre slope,liner& final mud bed forgot about the lath. Will it still work sitting on top of the deck mud and do i need to put some thinset down to adhere the stucco base to it? The he next one is measured like you said with tile (actually) pebbles on a sheet came out to be 1/2 inch left that much of the drain up just laid the tile in place just doesn’t look right. Can i use thinset to build it up more maybe 1/8 to 1/4 inch to have the stone sit proud of drain a bit. the drain is a tile in hidden drain 5 inch square. Any help will be greatly appreciated.
Hi Troy,
You need lath over the curb for the stucco to bond to. There is no way around that. To be able to answer your other question I need to know what specific ‘hidden’ drain you’re using. Tile can be built up 1/8″ to (maybe) 1/4″, but it depends on the thinset you’re using as well as the drain to determine what type of support is directly around the drain opening beneath the tile.
Mr. Elf……!
I am building my shower and got a lot of information from youtube videos – that could be good that could be bad! I found your site yesterday and have been reading page after page to find my mistakes and much to my relief I think I am OK so far. I have my final top mud deck done and today I was cutting and fitting tile. I have not “water tested” my work so I think tomorrow will find me doing a water test. My biggest concern is floor. I have a dip or two that I’m afraid will allow water to puddle. I was thinking that I could just “level” the floor with thin set as I put in my tile but I am not sure how “deep a dip” I could fill with the thin set. Is there another product that I could use to “level out my dips” that would be better than thin set?
I am sooooo Thankful I found your site because I was going to use the mix in a bucket to put my tile in my shower, but I believe I would be very unhappy with the mush I would be creating under the tile!
Jerry
Hi Jerry,
Normally about 1/4″ with thinset. If any larger just mix up a little more deck mud, put some thinset in the divot to bond it, and pack it in there.
WOW!! No, Double WOW. It is very rare to get an answer to a post so quickly so I Thank You so very much. I will measure my divot (are you a golfer?) and plan accordingly!
Jerry
Would it be safe to tape over the exposed threads on a round shower drain before laying the deck mud to allow for later adjustment. I am installing a pebble tile on the floor for the first time and I have concerns about the final grout being lower than the drain.
Also, do you have advice about how to achieve a wet look on the stone and grout?
Yup. Seal ‘n’ Enhance
Hi Vince,
Yes.
My aunt is now bound to a wheel chair and wants to make the shower wheel chair assessable. There is a dry pack in the shower now, am I able to install another dry pack over it or should I remove the old one & replace it with a new dry pack. The height needs to come up to the curb so the wheel chair will pass over.
Thanks Pat
Hi Patrick,
If the height difference is 3/4″ or thicker then you can install a new one over it. That is the minimum thickness the mud bed needs to be.
i have a question about the thickness at the drain on the preslope page you wrote (Your finished floor (after your liner and top mud bed are installed) needs to be 1″ to 1 1/4″ thick at the drain) then on the top mud bed page you wrote (your top mud bed directly over the top of your waterproof liner. The top bed will be 1 1/4″ to 1 1/2″ thick – consistent ) just a little confused over these two statements i guess my question is what should the thickness at the drain be of the preslope and then whats the thickness of top mud bed and then total combined thickness . i may just be over thinking this and it probably would work out during install but i like to stay 4 steps ahead of my self thank you
Hi Mark,
The total thickness from the subfloor to the top of the top mud deck should be 1″ to 1 1/4″. It can be split however you like, the top mud deck at the drain needs to be a minimum of 3/4″.
I am a little confused (this happens a lot). You say to “Place a piece of your floor tile on the base of the drain – on the upper part of the flange – and unscrew the barrel of the drain until you reach 1 1/4 inch.”
I know you can’t show all the pictures of the process, but where does this come in? I saw the picture of the 2 X 4 on top of the upper flange (I think that is what it is called), did you use this instead of the piece of tile? Why do you use a piece of floor tile for this? I apologize in advance if this is a really obvious question.
And thank you for your dedication to helping others.
Oh and I have a SQUARE drain, so I don’t think it can be unscrewed after it goes in, not sure if that makes a difference or not.
Hi David,
You need to have your square drain in place, oriented correctly before installing your top mud deck. The picture of the 2×4 is to get the height of the top of the 2×4 for the perimeter. Since the preslope is already sloped, the top mud deck will simply follow that slope at a consistent thickness. The height of the top of the 2×4 sitting on the drain will be the height of it around the perimeter as well. So in that photo the top of the 2×4 around the perimeter will be 4 1/2″ to get a consistent slope.
The tile for your thickness at the drain is so the top of the tile ends up at the same height as the top of the drain. If you don’t have the tile in there when you measure the top of your mud deck will be the same height as the top of your drain. You wand the top of your mud deck to be below the drain the thickness of your floor tile.
Did I just confuse you more?
i’m confused (not an uncommon occurrence). earlier you said the whole pan (plus tile) should be 1 to 1 1/4″. then you said the pre slope should be 3/4″ (at the drain). then the finish part of the bed should be 1 1/4 to 1 1/2″. that would be total of 2 to 2 1/4″. what am i missing?
Hi Tom,
If you have a topically waterproofed floor the total height is usually 1 to 1 1/4″, if you have a traditionally waterproofed floor the finished height is usually 2 to 2 1/4″. So where and in what context did I say it?
hello roger, i am impressed by your rapid response. the 1 to 1 1/4″ statement is in part 1, second paragraph after the heading, oh crap, math. thanks for clarifying the finished thickness. your instructions are thorough and much appreciated.
Oh, I gotcha. Shit, it confused me for a minute.
I prefer the finish part of the bed (top mud deck) WITH TILE to be 1 1/4″ to 1 1/2″
Unless using the thin mosaics my floor tile is normally 1/2″ or so with thinset, so the mud itself is 1″ – 1 1/4″. The important point is that the combined total of both layers needs to be a minimum of 1 1/4″ at the drain. Ideally this achieved with a 3/4″ preslope and 3/4″ top slope. However, the drain height on the preslope is determined by the height of the drain off the substrate. Ideally it should be 3/4″, realistically it never is. With a thicker top mud deck you reach the 1 1/4″ minimum height requirement at the drain. I really should change that to be more clear, thank you for pointing that out.
Hi Roger,
Fantastic site. Your tutorials are very thorough and way more helpful than any others I’ve read or heard. I wish I had found this site a week ago. My husband and I just bought a house and it has needed some serious work. I wanted to re-do our bathroom shower (which is a small 3’x3′ stall shower) and I was told to use regular cement for the base and not warned about protecting the weep holes in the drain. Now I have a dried cement shower base that I’m sure clogged all the weep holes. Should I chisel/sledge hammer out the cement and start over?
Hi Nicole,
Yes, you should. You can do it now or wait until your shower fails and causes damage to the surrounding structure. I’d do it now.
Wow, fast response! Thank you so much!
Elf,
After following your instructions the tee, I have ran into problemo… Long story short.. I am at the point where I am ready for my final pour of deck mud. BUT.. I am concerned about my drain height. I used the patented elf laser, 2×4 method and I ended up with a 5″ height. First problem 5″ puts my final height above my finished curb (don’t think it supposed be that high and according to my shower dimensions which are 5×3 I am only supposed to have an 1-1/4″ finished height for final deck mud. Those calculations came from the link provided on this site. So, correct me if I am wrong that with the 5″ height for the drain, I am doubling the amount deck mud. At this point I have read myself to oblivion and the answer I know is just an elf throw away…. Any help would be greatly guarantee my trip to the cuckoo’s nest will be delayed temporarily… Thanks!!!
Hi Scott,
The 5″ height should be the top of your 2×4, no? When you subtract the 3 1/2″ for the 2×4 it’s 1 1/2″. Or am I misunderstanding you and your deck mud is 5″?
Roger,
You are correct. To the top my 2×4 is 5″, minus 1-1/2 where the drain is screwed out to. Is 5″ where the top of my deck mud will be or am I missing something?. It seems awful thick. Thanks again Roger.
Scott
Now I’m confused.
Once you have your liner in and your drain screwed out to where you want it, set the 2×4 on top of it and measure from the liner to the top of the 2×4. That will be the same measurement at the wall (your pre-slope is consistent).
For instance, if, when you set your 2×4 on the top of the drain, the height from the liner to the top of the 2×4 is 5″ then the line from your laser should be 5″ high from the liner. This would make the depth of your top mud deck 1 1/2″ (5″ minus the 3 1/2″ of the 2×4). The 5″ isn’t the thickness of your bed, it’s the thickness of the bed plus the width of the 2×4.
Roger,
Sorry for the confusion. I completely understand now. I was thinking that the 5″ dimension was the finished depth. My bad. I appreciate your patience.
Hi Nichole,
Unfortunately the liner needs to go beneath the curb. So you can install your liner up and over what you have and put more mud over it, or tear it out and start fresh. Up to you. If he points and laughs at the curb, just point at certain parts of his anatomy and laugh – he’ll shut up.
Great explanation and I am tracking. However, in my 48″x48″ shower on a plywood base, the plumber installed the bottom half of the PVC deck drain flush (completely) to the floor…..as if there would be no pre pitch. In order to have any pre slope thickness at the drain, the mortar base will be higher than the bottom half of the drain that is affixed to the floor. Is there some sort of spacer that can be glued to the bottom most face. Such a spacer would presumably have to include a new set of holes to bolt the top half of the drain.
Hey Dave,
Plumbers always do that.
You can have a 1/4″ thickness at the drain on your preslope, it won’t hurt anything. Just make sure you have the full thickness on the top deck.
The wife found your site ( the BLACK VELVET has been disapearing ). We have the preslope in,the liner and backer board is up. the final mud we are in disagreement as to the way it goes in with a slope. We took a tub out so it measures 30×60 and the drain is 2 inchs away from the end wall.We aren’t in agreement
for the top deck.
Hey Rick,
The top deck needs to be level around the entire perimeter at 1 1/4″ above the drain.
Sorry about the Black Velvet.