The Shower Drain

The idea here is to have a claw foot tub with a shower but not have that all encompassing shower ring that makes you feel as if you’re showering in a condom. At the same time, I don’t want the shower stall type installation with the 6-inch curb and the thick build up of a sloped cement floor. A large portion of the water will be contained in the tub, but some of it will splash off the body and go over the side. It is this water that presents the challenge. Keep in mind when reading this that it will be virtually impossible to walk on this floor, because the tub will take up all of the space. This is a tile floor made up of half-inch thick tiles under a claw foot tub.

First some ground rules for this series of posts. To all of the nattering nabobs of negativity who will be chomping at the bit to fire off a comment telling me I’m doing it wrong as you’re reading this, please save your keystrokes. With all due respect, just because you read something some place that tells of a different way to do it, does not necessarily make you an expert, so please keep your doomsday opinions to yourself because I don’t want to hear it. If anybody wants to leave a comment regarding any of the topics in the following list, you will be wasting your time. It’s not my fault that you lack the ability of creative thought and are afraid to try something that has not been explained to you by a professional.

Yes, I familiar with the John Bridge tile forum
No, I didn’t ask them what they think about the installation
Yes, I know about Terry Love’s tile forum
No, I didn’t ask them what they think about the installation
Yes, I know this hasn’t been certified by some ANSI geek in a lab coat
No, I don’t think I’m going to destroy my house
Yes, I know about “wet floor” installations
Yes, I know that a traditional shower stall could have as much as 3-inches of cement
No, I’m not using a Kerdi Drain system
Yes, I know how to properly mix cement and sand for this type of mud bed
No, it is not too thin of a mud bed.
Yes, my old redwood plank sub floor is thick enough
No, I don’t think plywood would have made a better sub floor


Now that we understand each other, let’s move on.

The first plan was to use 3M’s 5200 Marine Adhesive Caulk to caulk each tile instead of grout. As a note of interest, when I first mentioned this idea it was poo-pooed by a few readers. Some even sent me emails telling me this was a bad idea and would never work. The funny thing is, none of them said they had used or even heard of the product. I mean, if someone emails me saying they’ve used the product for the last 10 years and said this may not be a good application for it, I would thank them. To just fire off an email when you have no idea what your talking about, I find a little insulting. Another interesting point is that while I was researching the product I found a professional tile installer who regularly uses the 5200 caulk on marble tiles in shower stalls because he doesn’t want grout lines. That’s right, I said no grout.

I bought a tube of 3M’s 5200 Marine Adhesive Caulk. First off, it ain’t cheap at all. It is roughly 10 times more expensive the your average 30 year door and window caulk. I did tests with silicone caulk, polyurethane caulk, and the 3M caulk. I took several tiles and glued them together to see how each caulk held up.

The tiles are the Oberon Saloon tiles and they are a half inch thick, unglazed porcelain tile. Silicone caulk worked about as well as toothpaste on the almost polished edge of the tile. The polyurethane caulk was better, but failed very quickly. The 3M caulk would flex more than a quarter of an inch before peeling away from the tile. Given that I am doing 1/16 inch grout lines, that means the tiles would need to separate 4 times their installed tolerance before failure. I don’t think that’s possible, unless I were to be hit with a 8.0 earthquake.

The real problems with the caulk idea are the installation and the color. The installation would be beyond tedious. These are 2-inch hex tiles and it would take forever to install each tile and clean up the caulk that oozes out as I go. I don’t think it would be a good idea to let this stuff dry on the surface of the tile. After all I’ve been through with salvaging and cleaning the tiles, I’m not sure I could go through that. The other issue is the white color of the caulk. I’m doing gray grout, and it would look odd to have two different colors of grout in the room. So I ditched the idea.

Then Aaron over at HiP told me about an article in the March issue of Fine Home Building. They were doing something similar to me. They wanted a shower that had no curb. Theirs was not a claw-foot tub, but just a regular shower. What they did was frame the floor of the shower area 4 inches lower than the rest of the room. They could then build back up to the rest of the floor in the room and still have the slope towards the drain.

This is great idea, but it is better suited for new construction. For me it would have taken major reframing of the bathroom floor, and I wasn’t really prepared to do that. I thought and I thought and I thought and I thought and I thought and I thought and I thought….and then I thought some more. There must be away to achieve what I want. Then a few weeks ago while I was plastering the bathroom, an idea came to me. It was odd. I was in the yard hosing out the mixing tub and thought, why not lower the existing floor in the tub area just a few inches. I thought, what is the point of going down 4 inches and then building back up with cement.

The tub area is about 5 feet long. With the drain in the center, if I need a quarter inch per foot slope, then that is only about a half inch of slope I need. So I started to wonder what is the minimum thickness of the floor I would need. The drain for a shower stall has a main drain and then a supplemental drain. There is a membrane under the floor that catches water that inevitably gets under the tile. This water makes it’s way along the membrane and drains in to the supplemental drain.

You need to have a sturdy floor on top of the membrane to set the tile. You can't have any type floor that needs to be fastened with nails or screws, because they would poke a hole in the membrane. This is the reason for all of the cement. You build up the floor in layers. You start with a flat floor and build up a “pre slope”. This is for the membrane to sit on and it slopes towards the supplemental drain. Then you pour the main cement floor on top of this. This creates the main slope of a quarter inch pre foot slope so water drains properly in the shower.

So what is the minimum thickness of this floor. Well, at it’s lowest point at the drain it is 1.25 inches (or 1.5 inches, depending on who you ask). It gets progressively thicker as it moves away from the drain. I went to one of the tile forums and asked a serious of questions. I never really said what I was doing, because I would get a hail storm of people telling me I was crazy. I’ll be honest with you, I have no idea if this will work, but you know the old saying, no gut’s no glory. If this is a failure I'm perfectly secure in the fact that I tried and failed, and I will go to a traditional shower ring. But how will I know if it will work or not unless I try.

Anyway, I had a excruciating series of discussions with tile guys and it was eventually decided that if the floor was flat then an inch and a quarter cement surface was sufficient to set tile. That’s all I needed. I just need to come up with an inch and a quarter at the edges, and an inch and three quarters at the drain. I need the quarter inch per foot slope at the drain, that’s the reason for the extra half inch there.

The rest of the room has half inch cement board on it, so you can lop a half inch off all of those measurements. So now I only need to come up with three quarters of an inch at the edge and an inch and a quarter at the drain. If I can do that, I can cover the whole area with an inch and a quarter of cement; create the slope; have the membrane; have the supplemental drain. Wham-bam-thank you mam! There is also the issue of conatainment. Remember, I don't want the curb, but more on that later.

So starting on Saturday, I pulled up the sub floor and started shaving joists. I basically created the entire slope of the shower area by trimming the tops of three or four joists. I started with the most inelegant of tools – the reciprocating saw – and finished them off with a hand plane. It went pretty well. I had to add in some extra framing, but it wasn’t too bad. You need to consider that I’m starting with full dimensional 2X10 joists so even if I take three quarters of an inch off the top, I still have more wood than a modern 2X10. Still, the floor is open, and I had the lumber and piers from the 2 story addition I took down, so what the hell. One things for sure, this is now the firmest floor in the entire house.

It’s still a work in progress and I’ve been taking lots of pictures. Tomorrow I will put in the membrane and pour the final cement floor. It should be very interesting and I still can’t say how this will work. There are still a few question marks and I’m sort of making it up as I go along. As always, I expect the worst and hope for the best.