Ryan's "How to build a shower pan" Page

Last updated: July 4th, 2004

Finished shower.

Ahh, so you want to build a fancy custom-sized shower pan. Well don't. It's a lot of work. Not convinced? Ok fine then. Have it your way. Here's my quick reference guide to building a custom shower pan. Mostly I'm going to tell you about the things that nobody else's web site mentioned.

By the way, I'm an amateur, so don't take my word for gospel.

These web pages helped me out immensely while doing mine:



Here are the fundamental steps:

  1. Rough-in shower drain pipe
  2. Prepare floor and walls for concrete and membrane
  3. Install base of drain.
  4. Lay thin layer of concrete to create slope
  5. Put down layer of roofing paper
  6. Cut and install membrane and top of drain.
  7. Hang concrete board on walls
  8. Pour final layer of concrete with chicken wire embedded
  9. Build form for threshold
  10. Pour concrete for threshold
  11. Tile it.
If I had to do mine over, I would have ripped out the linoleum and particle board that was above the plywood floor surface. At the time I thought it would be too much work, but it turned out that I needed to rip it out for the rest of the bathroom anyway and it really wasn't so terrible. You need to install backing for the concrete/membrane up the walls 6 plus inches up the wall. (Be careful not to leave any nail heads available to possible puncture the membrane once it is installed.) Also, you'll need to install the bottom of the drain assembly so that it lies flat on the floor.

Floor and walls are prepped for concrete.

You need a sloped floor in order for the membrane to flow water into the drain. So you'll put down a thin layer of concrete and slope it to 1/4" per foot. This layer ends up being very thin (1/4" to 1" at the sides), but that's ok because it will have a thick (2+") layer of concrete above the membrane.

Concrete slope poured.

Next up you'll put down a layer of roofing paper. This is to protect the membrane from being abrased by the concrete below it.

A layer of roofing paper protects the membrane.

Now comes the fun part. You'll cut a membrane to travel up the walls 6" and over the threshold. This is your last line of defense against water damage, so do it right. Glueing/bolting the membrane to the drain is covered in several other resources, so I'll let the reader look that up. It was pretty straight forward. You'll need to glue in place any outside angle pieces, and we found that the glue from Chloraloy was difficult to use. I would recommend looking up other options like a marine glue or something. Also, I've read other pages that say to glue the membrane to the floor/walls in order to get rid of air gaps that can pinch the membrane and leave the top layer of concrete less-supported by the floor/bottom layer. Also notice that I ran a continuous sheet of membrane down the wall from the shampoo nook to the pan.

Membrane installed.

Next up, put the bottom of the concrete board up. The poured pan will overlap the concrete board on the walls this way. Leave about 1-2" gap between the bottom of the board and the membrane to avoid a siphon effect up the walls. It would also probably be a good idea to thinset the corners now.

Concret board installed.

Now Tom and I poured the top layer of sloped concrete above the membrane for the shampoo nook. There's also the slope layer below the membrane.

Concrete poured for shampoo nook.

Now we pour the thick slab of concrete for the pan. This is the 2-3" layer that will provide strength to the floor and hopefully send most of the water to the drain. Remember to put your pea-sized pebbles around the drain to keep the concrete from clogging the weep holes. The picture shows that halfway through the pour, we placed the chicken wire down.

Chicken Wire placed in concrete.

The biggest issue I had with my project was not having an extension of chicken wire to wrap over the threshold. Without this, there would be nothing holding down the threshold concrete. The instructions I was following from the internet failed to mention this bit of news. So after my pan was poured, I had to use an impact drill to CAREFULLY drill 1" holes in the pan large enough for rebar and chicken wire to be glued in place. I used a marine-quality adhesive. Since the outside of the curb shouldn't get much water, I could screw concrete backerboard directly through the chickenwire and membrane to the 2x4s.

Lesson: When you do this, make your embedded chicken wire long enough to extend up through the floor of the pan and wrap over the curb.

Form in place ready for concrete on threshold.

And here it is all done.

All Done..