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.

diagram of a shower floor

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.

Location of Weep holes in shower drain Location of Weep holes in shower drain Weep holes in drain covered with pea gravel

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″.

Measuring drain for top mud slope Marking line for top mud bed slope

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.

Creating a level perimeter a shower floor Creating a level perimeter a shower floor Creating a level perimeter a shower floor

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. :D 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.

Ensuring a Level Perimeter
Figure 6

In the next post we’ll finish up your floor, fill in the center and get ready for tile!

{ 232 comments… add one }

Leave a Comment

 
  • John

    Hello, I would appreciate some help as I rack my brain trying to fix my problem. I have installed my mud floor (dry pack) using the quick pitch plastic risers to aid in the pitch of this floor 4′ x 6′ with drain offset slightly. The home owner had me install a square ebbe drain which once the mud was set and I did a dry fit the pebble stone floor in place I’m about 3/8″ from the top of the drain. ( I figure an 1/8″ or a little more of mortar will take up some height) I’m considering taking 1″ strips of 1/4″ thick cement board and using thin set to “stick them in place” as new guides filling in between with thinset or sand topping. (just not sure what is best for this 1/4″ of thickness) this should bring the stone pebble floor up to proper height once mortar is put down. I’d just like some professional opinions if possible. Thanks so much! John

    • Roger

      Hi John,

      You need to make up that difference with more deck mud. If you put down thinset, then more deck mud to bring your floor up to the correct height you’ll be fine.

  • doug

    Ive read an article you posted about prepping a wall for tile. I cant find that exact article, but its a quick question. I used hardibacker500 for my walls and compounded the joints. The next step was to primer the compound so mortar sticks. I was wondering if there was a certain primerthat works the best given the moisture.

    • Roger

      Hi Doug,

      If you’ve used regular drywall compound on the joints you need to scrape or sand that off. You need to use thinset with the tape inside the shower. You can not ‘prime’ it with anything, once water hits it the compound will release from the backer. The article is here: backer for showers There is a search box at the top of the page if you need reference to something else.

  • Gary

    Your site is awesome, I’m learning a lot. I have a couple of questions about the PVC pan liner. I see that it’s sold in 5’x6′ sections. It turns out that my shower is wide enough that the 6′ length isn’t quite enough to go up the wall a ways on one side and up and over the curb on the other side (another 8-12 inches would be perfect). Is there a reliable way to join additional material on with confidence it won’t leak? Or do I need to spend $200 to buy a 5’x40′ roll and waste all the extra? One other question. I see the dams you can use in 90 degree corners which will work fine for several spots in my shower. However, we also have (2) 135 degree corners at each side of the door to the shower (see lame drawing below). Do you have any recommendations what to do there? Thanks!

    ====================
    = =
    = =
    = =
    = =
    = =
    = =
    ===============

    • Gary

      drawing didn’t post the way i thought it would, it removed all the spaces between the equal signs…trying again

      000000000000000000000000000000000000
      000000000000000000000000000000000000
      000000000000000000000000000000000000
      000000000000000000000000000000000000
      0000000000000000000000000000000000
      00000000000000000000000000000000
      000000000000000000000000000000
      0000000000000000000000000000

      • Roger

        Hi Gary,

        The same liner-specific glue that you use to glue the dam corners in can be used to seam the liner. The funny angles can be cut, overlapped, then glued together as well. It’s like origami. :D

        • Gary

          Hi Roger – Thanks for the answers! Found out my Home Depot opens the big rolls and cuts to length which was handy.

          Anyhow, I have another question. I just did my preslope yesterday. Considering I’ve never worked with concrete before, I think it went *fairly* well. I have a nice straight slope from all points in the floor down to the drain with the right amount of slope. The only thing that concerns me is the flatness/uniformity of the surface. In some places I was able to get it quite smooth but in many other areas there are little pits (not big bowls or valleys) that may be 1/8″ of deep. Should I be concerned about those? Should I mix up some thinset or something and try to fill them in? Thanks in advance.

          Gary

          • Roger

            Mix up some thinset fairly thin (runny) and skim-coat the entire floor. That will fill in those pits as well as lock in any loose particles (the sandiness of the floor).

            • Gary

              Thanks! Quick follow up – I see there are all sorts of thinset products, what would you recommend here? Is that the same thinset that I would then use later for tile installation?

              • Roger

                Yes, same modified thinset you’ll use for the tile.

                • Gary

                  Hi Roger – I got the preslope done, it’s pretty awesome now. Nice and flat and marble goes straight to drain no matter where I put it. I’ve got the shower liner installed in the drain and tucked back into my 90 degree corner in the back corner of the shower. But, I am attempting to install the first dam corner and I don’t know wtf I’m doing. I followed the advice cutting from the top inside corner straight out the edge of the curb, but it seems like there is way too much liner material to bunch up in any reasonable way. Plus, the dam corner piece is too long and wants to bunch up somewhere. It’s hard for me to tell from the pictures you posted of this step what I’m supposed to do.

                  We may need to buy a new liner after your advice, but i’ll tell you where we are at. We cut from the top inside corner to the bottom inside corner and then removed a lot of the excess liner that would have overlapped. What this left was about a 1/8″ gap down the inside corner which we then covered with a dam corner. Unfortunately, doing it this way, there is clearly not 2″ of overlap, there’s probably 1/2″ to 1″ of overlap from the bottom of the cut in the liner to the edge of the dam corner. I have a picture of it if there’s an email address I could send it to so you can see what I’m talking about. Is that possible?

                  Any advice would be greatly appreciated. Thanks.

                  Gary

                  • Roger

                    Hi Gary,

                    Provided you got plenty of adhesive on there and it is solidly bonded you don’t need a full 2″ overlap. With that liner and adhesive 1/2″ will actually be just fine. Just ensure that you have it bonded well.

                    • Gary

                      Hi Roger,
                      I ended up ripping out the first liner and doing it again. It came out much better the second time. I’ve now got the whole shower floor and curb complete and tiled! Feels like I’m making real progress now. Anyhow, I have another question for you. I used SpectraLock Pro grout like you recommend but I’m not sure whether I’m supposed to seal it (and the tile) or not. I thought I’d read somewhere on your site that when you use epoxy grout like SpectraLock that you don’t need to seal it but then I thought I saw somewhere else that you should always seal regardless of grout. If I should seal it, what sealant would you recommend?

                      Thanks,
                      Gary

                    • Roger

                      Hi Gary,

                      No need to seal it.

                    • Gary

                      Update: Just found your articles on sealants. Very helpful, thank you! But now I’m not sure what to do. I would like to seal, but unfortunately I’ve already grouted the floor (2″x2″ porcelain) with SpectraLock Pro. I’d like to use Miracle Sealant’s 511 Impregnator like you recommended but have I missed my chance? Will it do bad things to the SpectraLock if I just cover the whole floor with it?

                    • Roger

                      Hi Gary,

                      You can still seal over all of it if you want to.

                    • Gary

                      Update 2: found info about sealant and it looks like it’s fine over grout so ignore all my previous questions. But, I do have one question which I don’t think I can find the answer to. I’d originally bought your manuals for both the Traditional shower waterproofing method and the topical membrane approach because I wasn’t sure which way I wanted to go. Well, I built the floor using the traditional approach and I’m now thinking I’d like to do the liquid membrane on the walls. Is that OK? Specifically, I’m worried about the ‘mold sandwich’ I’ve read about on your site. I would have that sandwich for about the first foot up the walls of the shower where I have the PVC liner behind the hardibacker and the topical membrane on the front of it. Would you recommend not doing that? would an option be to redgard everything on the walls except that first foot off the floor? Or should I just stick with the traditional approach and hang plastic behind the hardibacker before I put it up? Thanks.

                    • Roger

                      It won’t be a problem in the bottom foot of the wall. You can topically waterproof walls over a traditional pan.

  • Doug

    I am starting the process of installing my shower base and, at the moment, all I have is a 2″ pipe sticking out of the concrete floor. My question is do I chip out the concrete so that my drain flange sits flush with the floor? And if so, if my chipping is not perfect do I need to refinish the floor with concrete so it is all tidy before I pour my pre slope?

    • Roger

      Hi Doug,

      It doesn’t need to sit flush but you can chip out enough to get it wherever you want. You can simply fill any excess with deck mud.

  • Chris

    Hi Roger –

    I have a few questions, so I figure that it might be best to explain what I’ve done so far and then ask them…

    I put in my pre-slope, PVC liner, water tested and then put in my top deck two weekends ago. The slope is generally good, but I’ve got one corner that has a bit of a high, and corresponding low spot. Yesterday I noticed that the top bed has a hairline crack – and I am planning to get to tiling the floor within the next 10 days (25-30 days after finishing the top deck).

    Now the questions:

    1) I’ve seen some information that says not to “finish” the surface as it can impede water penetration. Mine was fairly smooth – should I be concerned, and can I fix it if needed?
    2) I had not seen your site and information regarding ensuring that the weep holes remain unplugged. I don’t know if mine are plugged or not, now! Is there a way to check this before I go any further?
    3) Is there a good way to grind / level the high spot as it is pretty hard. Can I use thinset to level low spots, and then tile the following day after the thinset leveling has hardened?

    Thanks in advance for all the helpful info on this site!

    Chris

    • Roger

      Hi Chris,

      If the deck mud was mixed correctly then you don’t need to be concerned about it.
      You can just plug the very top of the drain, leaving the weep holes inside the drain open, and fill up the base to see if it drains (it’ll drain SLOWLY)
      You can grind it down with sandpaper or a brick (yes, seriously) and yes, you can fill low spots with thinset.

  • Mike Lipschultz

    Roger,

    I am constructing a shower pan with the curb on 2 sides of the shower. How you do you fold the liner on the inside corner where the curbs meet?

    Thanks,
    Mike

    • Roger

      Hi Mike,

      Cut it from the inside top corner out and overlap it at the corner and glue it.

  • d scott christian

    Roger,
    Great advice on building shower pans. I’ve finished mine following your instructions but now my top mud sounds hollow in places. My pan is built on concrete slab. I know the top concrete does not bond to the PVC liner but not sure if that would cause the hollow sound when I tap on it. Standing on it feels firm and there are no cracks in it. Any advice would be greatly appreciated.

    • Roger

      Hi D,

      It always sounds hollow. It’s completely normal. It’s fine. Really.

      Stop knocking on your deck mud. :D

      • d scott christian

        Thx, my first time at this, appreciate the guidance.

  • John

    Roger do you have to do anything to compensate for the thickness of the shower membrane on the area that goes on the walls so it does not push out the board. I realize this would be slight but I am curious.
    Thanks
    john

    • Roger

      You can either shim out the backer or create a pocket in the studs for the liner with a chisel. And you only need to ask once – I get every question in the back room in the same place. :D

  • kevin

    So I installed my tile on top of my final mud bed and was unhappy with how it came out, wrong trowel (now I know), and position/ spacing..Anyways, I ripped up the old tile and now I obviosuly dont have the nice slope I did before. Some chunks of the mud bed came out and some spots thinset stayed. What can I use to skim over the top to get a nice slope back? Bumps/divots are about 1/4″.

    • Roger

      Hi Kevin,

      I would scrape off the remaining thinset, then you can go over the whole thing with a layer of thinset to flatten it out again.

      • kevin

        So after cleaning up the rest of the thinset in 2 spots it broke chunks down to the oatey liner. I see now that was a thinner spot where it pulled up, some other spots got thin also. Can I add a thin layer of more deck mud, maybe 3/8-1/2″ thick?

        • kevin

          Any advice? I saw on part two if you need to patch to lay down thinset first, should I coat the exposed areas of liner with thinset as well as the whole bed then go over with another coat of deck mud? Thanks

        • Roger

          Yes, but you need to bond it to the existing deck mud with thinset. Just go over it like you’re setting tile, then install deck mud instead.

          And be prepared – it’s messy. :D

          • kevin

            I ended up ripping out the old deck mud and redoing it. Came out much nicer and tiles went down great this time. Thanks.

  • ChrisTopher

    Rodger,
    I have installed the vaper barrier, preslope, cement board, and membrane liner and final top coat. Can Red Guard be used on my cement boards seams and floor edges and curb?

    • Roger

      Hi Chris,

      Yes.

  • Mike

    Thanks Roger!
    Any limits to the depth I can skim? Also do I mix to the exact specs on the thinset bag, or add more/less water than usual?

    • Roger

      Just mix it normally. You can usually go 1/4″ or so, you can also do two layers if need be.

  • Mike

    Hi,
    So I followed all directions and got to the final concrete pan install. Thought I did a good job, but as I brought in the shop vac to eliminate the sand residue on top of my new concrete pan, chunks of the concrete came up. This was after 24 hours of cure. I think what happened is I let too much time elapse between mud packing the deck and returning 2 hours later (I have a day job) to make some finishing touches to the level of the whole pan. So, now I have a nasty surface that lost it’s beautiful slope and looks like the surface of the moon. What products can in use to skim coat or level this out and recreate my slope? I was thinking just a thin set mortar but I’d appreciate your advice. I’m only talking about maybe 1/2″ at the deepest. I hope the answer isn’t to chip it all back to the liner and start from scratch.

    Thanks for all the help! You’re awesome!

    • Roger

      Hi Mike,

      Now you have to burn your house down! That’ll solve it. :D

      Actually, you can just skim over the entire surface with thinset. That will work just fine.

  • Ken

    I’m confused. I thought you were supposed to slope 1/4″ per 1 foot. I’ve done this in the pre-slope and thought you were supposed to do this on the final mud bed as well, but based on your pictures, you have the drain at 1.25 inches AT the drain AND the wall which would mean there is no slope at all on the shower/tiled floor.

    Am I missing something from your pictures in Step 4?

    • Roger

      Hi Ken,

      You already have the slope on the preslope, the top mud deck, at a consistent thickness, will still be sloped at 1/4″ / foot. If you slope the top mud deck as well you will end up with a 1/2″ / foot slope.

  • Leo

    Roger,

    I was planning to use Mapei Aquadefense as a vapor barrier over the entire shower. Do I still use the vapor barrier (plastic sheeting) between the cement board and studs?

    Can I use the Aquadefense with a fiberglass mesh for the cement board seams and plane changes instead of thin-set and mesh?

    • Roger

      Hi Leo,

      No vapor barrier if you use aquadefense. No, you still need to thinset and mesh the seams. The AD will not tie the boards together. The mesh for the AD is to give it strength in vital areas so it doesn’t split apart.

  • kevin

    Do you try to get the backer board as close to pan liner as possible or is a 1/2″ gap or so at the bottom fine? Also, the for the barrel of the drain, it should sit above the top mud bed the thickness of the tile correct?

    • Roger

      Hi Kevin,

      You WANT a gap, backer will wick water. Yes, the thickness of a tile so the drain is flush with the face of the tile.

      • kevin

        Thank you, I am installing the backer before the final mud bed so I will leave the 1/2″ gap since my top bed will be 1″ thick, should be plenty of mud to hold the backer in place at the bottom.

  • James

    Hi Roger thanks for such and informative site. I really appreciate your hard work! I was wondering about the Mapei 4:1shower mud and would you recommend it? Sounds a lot easier than mixing everything else.

    Thanks
    James

    • Roger

      Hi James,

      It’s good stuff, and works very well.

  • Steve

    Hi Roger,

    I’d like to use a Noble linear drain in my basement shower which allows for a thin-bed or full-mortar installation. Which method would you recommend and why? I’d prefer thin-bed (for less height loss and quicker installation) but wonder if a full-mortar installation would protect better against cracks.

    Thanks!!!

    • Roger

      Hi Steve,

      Unless your shower is HUGE a thin-bed method works just as well as a full mortar. Go with the thin-bed.

      • Steve

        Thanks, Roger… I’ll give it a shot!

  • Mike

    Hello Roger,
    Enjoyed your site and instructions on creating a shower floor. One question, perhaps I just missed it.

    It makes perfect sense to me to never perforate the shower floor membrane… no holes implies no leaks which yields no upset wife. However, does the same concern extend to the moisture barrier which is behind the vertical substrate?

    I presume the moisture barrier is there because the substrate (cement board?) is not waterproof and the intent is that any moisture will flow down and eventually encounter the shower floor liner (overlapped into it). I also presume that the cement board needs to be affixed to the studs…

    -mike

    • Roger

      Hi Mike,

      You’re correct. However, the fastener will actually seal the hole as it is driven in. Not really ‘seal’ it, but it creates a ‘pucker’ around the screw which water will run around rather than in. Gravity helps on the walls, it won’t help on the floor.

  • Gramps

    When marking the line for the final mud application , I am a little confused with the math and diagrams. You mention 1 1/4 mud at drain , does this mean 1 1/4 plus the thickness of the floor tile and thinset, The drawings do not show the tile but the text does menthion it. Thanks for your help

    • Roger

      Hi Gramps,

      Yes, 1 1/4 total thickness of the mudbed at the drain from the substrate to the top of the mud. The tile and thinset thickness are above and beyond that.

  • matt

    Hello Roger,
    You mentioned that it is ok to put the cement backer board on before you mud the pans top coat. My only concern is about expansion & contraction. Will there be room for this? The manufacturer of the hardi board says to put it slightly above the shower pan so this is where my concern arises from.
    Thanks for all the great advice,
    Matt

    • Roger

      Hi Matt,

      You can do it either way, it will be just fine. The amount of sand in deck mud compensates for regular expansion and contraction.

  • Grace

    Thanks for your informative site! We are in the process of constructing the mud bed for our shower and can’t figure how long Mapei 4:1shower mud needs to cure before applying Mapei AquaGuard. Some sites suggest 72 hours. Can’t find any info on the Mapei site. Thanks!

    • Roger

      Hi Grace,

      72 hours is correct.

  • tom

    Hello and thank you for all the great information. Im also so very happy to see that you are very clear as to where the sep holes are. I don’t understand why i have watched videos and read other articles on how to by experienced people and the all don’t know where the weep holes are?

  • christopher

    Great website and very imformative. I just have a quick question and it might be a stupid one. Do you put something onto the final layer of deck mud before tiling it? If it is as fragile as you make it sound, what keeps the floor tile from popping off?

  • Mike

    Roger, I’m doing a traditional shower pan (three piece drain, pre-slope, liner, etc.), but I want to use Kerdi membrane for the shower curb and walls. I’m not sure how to integrate the two technologies and be water proof. The curb is three stacked 2×4’s and I have a plywood subfloor. The bench is out of 2×4’s as well.

    Can the shower pan liner, instead of being behind the cement board running up the wall about a foot, can I run it in front of the cement board then nail it at the very end and then thin set and Kerdi from pan liner midpoint up wall all the way to the ceiling. I kind of want to do the same with the curb and bench? I guess how do you transition from liner to Kerdi or Redguard and still have a waterproof shower?

    • Roger

      Hi Mike,

      You don’t want your backer imbedded into the deck mud, it can wick water behind your kerdi. Leave it about 1/4″ up and just run your kerdi down to the bottom. The kerdi on the front of your backer overlaps your liner behind the backer, gravity takes care of the rest. You’ll have a waterproof shower.

  • gary

    Thanks Roger,

    Sounds like a plan – have a few pints of homebrew before I start the pre-slope tomorrow.