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You are here: Home / Renovations / Bath Renovation / DIY Custom Shower 2: How to Build a Shower Pan

DIY Custom Shower 2: How to Build a Shower Pan

September 21, 2015 by SmartGirl 10 Comments

I’m sure you already know that the hardest part of building a custom shower is laying the concrete floor.  It’s also know as the shower pan or shower base.  You may have heard talk of a pre-slope or seen people wrestling with big sheets of black plastic/vinyl/rubber on TV.  You probably think it’s impossible to get just the correct angle on a DIY shower pan, one that allows the water to easily flow into the drain.  Or maybe you’re deathly afraid you won’t do it right and water will leak everywhere.  Hell, lots of professionals are intimidated by concrete shower pans.  My neighborhood plumber did his own shower pan and told me you couldn’t pay him to install one for someone else. Wow, I must be crazy for trying to build a DIY shower pan by myself!

Nope.  It really wasn’t that bad.  And I am not an expert, a contractor, or even a handy (wo)man. I have never remodeled a full bathroom before.  I have never built a shower pan.  I am just like you!  Well, maybe a little gutsier 😉  With this method there is no pre-slope, black liner, or liquid waterproofing to roll on.How to build a custom shower pan with Smart Girls DIY

There are several different methods to build a shower pan, but I decided to go with a mortar bed and Schluter Kerdi waterproofing membrane. But you already knew that from the last post where I build the shower curb.  There are 3 more components to my shower pan: the drain, the concrete (mud) base, and the waterproofing membrane (Kerdi).  We’ll talk about the first 2 today.  I recommend watching this video, which explains the entire process, as an overview before getting into specifics.

This is my video showing the whole DIY shower pan mudding process.

Schluter Systems has a ton of other videos for various installation situations, which is good because chances are your situation is not exactly the same as mine.  I think this is a huge reason home owners don’t try things themselves — you might find a great tutorial but it doesn’t apply to you exactly. You can use this tool on the Schluter website to make a customized video series for your specific situation.  Cool!

My specifics:

  • Concrete subfloor with a big hole around the drain pipe – so apparently I needed this video on Concrete Box Out Drain Preparation (who knew?!)
  • No access to the plumbing from below (it’s a concrete slab), so I watched this video
  • I watched this video long before I tiled, so I would know what to expect

Supplies I purchased are discussed in this post.  I also used some tools I already had: 12-inch finishing trowel, margin trowel, 5-gallon bucket, wheel barrow, shovel, and at least 3 levels.

Always check local building codes and get all permits and inspections necessary for your project.

Installing a Schluter Kerdi-Drain

I. Concrete Drain Box Out

A drain box out just means that I needed to make the hole in my floor smaller, leaving only enough room for the drain assembly.  This will give me a solid surface to lay my deck mud.Concrete shower subfloor needs the drained boxed out in order to support the shower floor

1.  Cut the riser pipe to the correct height first.  (The riser pipe is the black pipe sticking out of the ground, that I will attach the drain to.)  Test fit the Kerdi-drain assembly to verify the correct height.  It is definitely easier to cut the drain pipe before you build the box out, trust me I learned this the hard way when I had to trim it again later.

2.  Use 4″ pipe coupler to act as a protective barrier between the mortar and space around the riser pipe.  If the coupler is the correct height, lay it in place and check that it’s level.  If it is too short, begin to fill hole with mortar or concrete to bring the hole (and the coupler) up to the right height.  My hole was very deep and needed to be filled, so when I finished tiling the bathroom floor I added the leftover thinset to the hole.  This is what the pipe coupler looks like.

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3.  Fill the hole with thinset mortar, deck mud, concrete, whatever you have on hand.  I used more left over mortar from my floor tile installation.  It’s not pretty, but it’s effectiveConcrete box out drain preperation

4.  If you’re not installing the drain right away (because you like to work on 15 projects at once) then protect the opening by filling it with something like plastic shopping bags or rags.Preparing to build a mortar DIY shower pan

II. Attach the Kerdi-Drain

1.  Verify the fit.  Mine needed tweaking, so I shaved off a small portion of the coupler to make it the drain sit perfectly level.  You can see where I trimmed it in the labeled picture above.Kerdi-Drain was not yet level, so I had to fix it before I made my DIY shower pan

2.  Remove all dirt from the riser pipe and drain.

3.  Check the manufacturer’s directions for your adhesive and apply it accordingly.  My riser pipe is made of ABS, so I purchased an ABS Kerdi-Drain, and had to use ABS cement.  You DO NOT use primer with ABS cement.  The hardest part for me was opening the damn can.  It was sealed shut (maybe used and returned?) and in a panic to get it open before my deck mud dried, I opened the Oatey can with a can opener.  That meant I had to throw the rest out, but you do what you’ve got to do.

Oatey ABS cement

4.  Twist and lower the drain assembly over the riser pipe and make sure it’s level.

*If you’re really curious what steps 3 and 4 look like, or you don’t really believe that I do this stuff myself, then you can check out this terrible quality video, taken by my 7-year-old, just don’t come complaining to me when you feel nauseous.*  

5.  Support the bonding flange (wide, white part of the drain assembly) by filling in the area underneath with loose mortar.  You can use the same deck mud you’re going to use for the shower pan, just add more water. I jumped right into the mortar bed next…Pack loose mortar under the Kerdi-Drain for a DIY shower pan

Building a Mortar Shower Bed (DIY Shower Pan)

I. How to Make Deck Mud

Deck mud (also know as dry pack mortar, floor mud, or screed) has 3 ingredients; sand, portland cement (not masonry cement), and water.  People use various proportions of the 3 ingredients to get the perfect deck mud  and you can check out the John Bridge website for more info.  He recommends using a 5:1 ratio of sand to portland cement.  I ended up using a 4:1 ratio, but I did buy a 5th bag of sand just in case, I just didn’t use it.  First mix the dry ingredients, then slowly add water and mix until the mortar is dampened completely.  I mixed mine in a wheel barrow because I was too cheap to spend $13 on a concrete mixing tub.  The wheel barrow worked just fine, but I did make only half a batch at a time.  I also used a shovel, but a garden hoe would have been better.  FYI – I left the wheel barrow outside and carried the mud into the bathroom one bucket at a time.Mixing deck mud in a wheel barrow for a DIY shower pan

Deck mud should be damp enough to hold itself together, but doesn’t have any excess water.  The lack of water is what makes deck mud easier to work with, building the shower pan is like building a sandcastle, and the set time is longer.  The lower water content also keeps the mortar from shrinking as it cures, and shrinkage is not what we want for our shower pan.  Here’s a 2-minute video of me mixing deck mud.

II. How to Calculate Proper Slope

Like we already discussed, the main thing people worry about when building a concrete shower pan is getting the slope right. Obviously you need water to flow toward the drain, not away from it, so the rule of thumb is to have at least 1/8 inch of rise for every foot of run. Huh?  Just figure out which corner is furthest from the drain and measure the distance.  This tells you your “feet” measurement (the run).  Now calculate the rise by multiplying the by 1/8″.

Ex: If it is 3 feet from the center of the drain to the furthest corner, then your minimum rise is 3/8″, but you’d be safer if you went even higher.

Now that you’ve determined rise, you must add it to the height of the shower drain to get the final height.

Ex. Your drain sits 1″ off the ground.  Use your level to mark the height of the drain on the wall.  Don’t just measure up 1″ along the wall because your floor may not be level, which means your 1″ mark won’t be the same height as the drain.  Now that you have the drain height marked, add the rise and make a second mark.  It is this second mark that determines the final height of the shower bed.

III. Let’s Build this Shower Pan Already

1.  Mark the perimeter height of the mortar bed. Schluter doesn’t say to do this, but I made a line on all 3 walls, and the inside of the curb, indicating the final height. (This is the Schluter video)

2.  Mix the deck mud. (see above)

3.  Start along the perimeter and build a mortar screed (a wall of deck mud).  Tamp and level it using the handy line you drew in step 1.  Here is the beginning of my perimeter screed.  Beginning to build the perimeter screed for my deck mud shower base - DIY shower pan time!

4.  Pour the deck mud (dry packed mortar) into the shower and spread it with a trowel.  (The stuff in the bucket above is the loose mortar I mixed up to use under the bonding flange, not dry pack mortar.)  Tamp it down and slope it from the perimeter toward the drain.  You already took all your measurements, so just play with the deck mud until it’s smooth and nicely sloped.  If the perimeter is always the highest point and the drain always the lowest you don’t have to worry about the rest.

Here it is almost finished, then completely finished.How to build a DIY shower pan out of dry pack mortar - almost finished hereFinished my DIY deck mud shower pan with a perfect slope

5.  Wipe any mud off the drain. And everywhere else, for that matter.

6.  Allow the concrete to cure overnight.  The moment of truth — checking that the perimeter is level and everything is sloping toward the drain.  Woohoo!  We’re all good!You can build your own DIY shower pan, it's really not that hard

My DIY Shower Pan

It took me 1 hr 17 min to get from step 3 to step 5, but I did a lot of fiddling around with it.  I thought it was over 3 hours until I was able to recover the video I took of the whole process.  For months I thought it was lost forever, my computer was showing it was a corrupted file.  Well… thank goodness, I was able to get it back and now you can enjoy that 77 minutes for yourself, sped up to 16-32x speed of course!

Did you know you can pin videos to Pinterest too?!  Go for it!  Or use this.Build your own concrete DIY shower pan -- it isn't nearly as hard as you think!

Next step is to add the Kerdi waterproofing membrane!

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Filed Under: Bath Renovation, Featured, How To, Product and Reviews, Renovations, Tutorials Tagged With: bathroom, plumbing, Schluter

Previous Post: « DIY Custom Shower 1: Supplies, Walls, Curb
Next Post: Make Your Own Drawer Liner – Quick Tip Tuesday »

Reader Interactions

Comments

  1. Lou Lou Girls says

    September 28, 2015 at 12:31 pm

    Great post! Pinned and tweeted. We love partying with you and we appreciate you stopping by! Please take a minute to stop by next week, so we can pin and tweet your new creation. The party starts on Monday at 7 pm! Have a great Monday! Lou Lou Girls

    Reply
  2. Holly says

    October 6, 2016 at 10:20 am

    Such a great job! I am planning my basement bathroom remodel now and remembered your IG post about building a shower pan. I had no idea it would be so thorough! Yay for you!!

    Reply
    • SmartGirl says

      October 6, 2016 at 12:15 pm

      Lol Holly. That’s my problem, I write so much that it takes me forever! Thanks, I sure hope it helps with your remodel.

      Reply
  3. liz says

    April 24, 2017 at 10:08 am

    Thank you for these posts!!!

    Reply
  4. Allyson says

    June 6, 2017 at 8:17 am

    You are literally WonderWoman. Thanks for this post!

    Reply
  5. kai says

    July 21, 2017 at 10:18 pm

    After all that, is it ready to go, or are you planning to add title to the floor?

    Reply
    • kai says

      July 21, 2017 at 10:18 pm

      *tile

      Reply
    • SmartGirl says

      August 19, 2017 at 12:44 pm

      I added tile, same ones I used on the bathroom floor, just have to update my posts. The tile doesn’t provide any waterproofing, as I guess I had always assumed it did, but still necessary, I guess.

      Reply
  6. KM says

    March 8, 2018 at 8:08 pm

    Hi, I stumbled on this site after already installing my Shluter Kerdi drain + floor pan. I thought I’d already watched every Shluter Kerdi video on You-tube, and was looking to refresh my memory, before starting the mudding of the holes (from screwing the walls in), and doing the corners. I was curious how your experience was, and see you made your own mud base, rather than use theirs, but the Drain was the biggest nightmare for me, because no one (including you) mentions that the Kerdi Drain wants that 4″ coupler, but neglects to mention that it’s a PRECISION fit!!!

    Shcluter videos all suggest adding that 4″ coupler like it’s an afterthought, and wouldn’t it be nice to have a little finger room around the drain pipe, and oh, yeah, it also helps support the drain. It doesn’t “help” support the drain – it just BARELY allows the drain to drop down into that 4″ coupler, and it’s a TIGHT fit! If you’re off center by an 1/8th inch in any direction, you’re not going to be able to mate your Kerdi drain with the drain pipe! And heaven help you if you drop it in crooked!

    I learned this the hard way! I tend to like neat, so my drain coupler was fairly centered, anyway, but not close enough! I literally had to get my reciprocating saw, and wail away on the 4″ coupler (already cemented into the hole), and pray that I wouldn’t nick that drain pipe while I was at it.

    Thank goodness I’m fairly anal about such things, and I only had to shave off 2/3s of the coupler edges to get it to fit, but had I been more casual about just lobbing that thing in there, I’d have been in some real trouble. Do everyone a favor, and specify that centering that 4″ coupler is imperative, or the the drain won’t fit at all! I have no idea why even Shluter doesn’t seem to state that clearly. I didn’t have the drain yet, when I filled my hole and leveled my floor, so I had no idea that the stupid thing was such a tight fit. No ONE online mentions that, and they skip right over the showing parts. Just, hey, drop one of these couplers in there, so it leaves a bit of finger room, and will support the drain better, to boot. They NEVER show how it fits just sooooo tight in the coupler! BIG Headaches to follow!

    Also, I too had a hard time figuring out how I was going to cut my drain pipe below ground, to match the depth of the drain kit. Until I got my Dremmel tool with a wand, and hung it over the hole with a tripod. Once I suspended the tool wand over the hole, it was super easy to use a cut off wheel to cut a perfectly level edge from the center out, and I never even needed to see into the hole, or worry about going off level. It worked great, and because I had to go shallow for the first cut, it was super easy to adjust the tripod down the quarter inch I was off, and cut it a second time, to a Perfect height. Perfectly level, and not even any burrs to clean up. Smooth as silk, and ready to bond. Hope that helps the next person, having the same problem. Thanks for the video, and forum. Wish I’d seen it sooner.

    Reply
  7. Gary Mustain says

    March 28, 2018 at 8:31 am

    Slope should be 1/4″ per foot!!!! This is the absolute MINIMUM SLOPE PER CODE! You should not give “How-To” advice if you don’t know “How-To”!

    Reply

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