We are in the process of interviewing several potential contractors. After these screening interviews, we will ask for bids from the 2 or 3 contractors who are most knowledgeable and compatible with us and our project. We know what we want for most parts of this bathroom, but we are still trying to understand the best way to design an accessible shower. We want to add it now as we rework our main floor so that we can eventually "age in place". The four contractors we have spoken to so far have looked at the joists, sub-floor and open access from below; and all confirm that we can readily recess the floor under the shower. They differ, however, in how they would handle the shower pan and drain for this curbless accessible shower. A couple of them have suggested the Wedi system with a linear drain. Another talked about the Schluter system, and a fourth contractor said his tile man only does a traditional mud base with a central drain. They all said that floor in the main part of the bathroom could be level and the sloping would all occur within the 4' x 4' shower (1/4" per foot). Most would put waterproofing under the whole floor, but one typically extends the waterproofing just a foot or two beyond the shower entrance. Are there reasons to go with the traditional mud base vs the Wedi (or other foam type backer)?

We have a zero entry shower. It has a regular round drain. We have no problems with it draining properly. HOWVER, when your contractor says he will "lower the floor via the floor joists", if you have i-beam joists make ABSOLUTELY certain that he is not thinking he can cut down into the top edge (flange) if the i-beam joists. The flanges of i-beam joists CAN NOT be cut. If the flanges are cut or knotched, the joist loses structural integrity. Do NOT let him cut or knotch the flanges...even if you have to give up on the idea of a curbless shower entirely. Before we fired him, cutting the top flange of the floor joists running under our second floor master shower was just one of the many mistakes our sorry-a22ed builder made! He had previously ignored our architect's carefully designed joist specifications. If he had followed the specs, the master shower area (and our laundry room) would have been framed with their floors about 4 inches lower than the rest of the second floor. Instead he figured it would be cheaper to run longer joists and then just "cut the floor down" in those two areas. It cost us a minor mint to get that mistake fixed so that we didn't have to worry about the joists caving in! And we were only able to fix the mistake - and still have a roll-in shower - because the shower had been positioned so that it was sitting squarely over two walls downstairs that could be used as additional support walls for the i-beams the builder had cut plus some new, shorter joists that had to be run under the shower floor. (The guy who installed the new joists had to do acrobatics to retrofit them in.) Fortunately I stopped our builder BEFORE he cut the the flanges on the i-beam in our laundry room. There we solved the floor drain problem by building a raised section with a sloped floor for the washer and dryer to sit on...basically a raised "shower floor." If you wanted a curbless shower at the start, your architect should have specified in detail how the floor framing should be done so that no i-joists would need to be cut. If your curb-less shower is a "change order," please do yourself a favor and hire an engineer to design exactly how the change can be made without sacrificing the integrity of your floor joist system. If your floor joists are SOLID wood, maybe they can be cut down enough to accommodate the curbless shower. I don't know. Since our builder used i-beams throughout, I didn't wind up having to educate myself on what is allowed when cutting into and knotching solid wood joists. I'd still strongly recommend you get an engineer's opinion before allowing him to cut down the joists. It might cost you a couple of hundred bucks but better to be safe than sorry. Our curbless shower is large enough that we don't have a door on it so I can't respond to the question about the door going over the carpet.

Thanks so much. I now understand so much better. Our foundation is "pier and beam" but as you indicate, that is still probably not or may not be a simple task to lower. But now I see that if there is a linear drain and you luck out with the door to the shower in the right place relative to the joists, the linear drain can very likely simplify the task (in addition to making things look sleeker). Our shower will be 5 X 5 which means the slope would be even easier to implement without obvious detection. Though I now see why some documentation I've read indicates a "secondary drain" outside the shower is nice to have. If the water in the shower overflows past the linear drain into the room, the secondary drain can cover that but then with the secondary drain, you are faced with needing to slope the floor in the main part - i.e. lowering joists or maybe finding a place between joists - another engineering task. I also now see why what shower fixtures are chosen and how to implement makes a difference here. If your fixtures (i.e. running hand held plus standard shower head plus rain shower simultaneously) allow for a LOT of water simultaneously, then the likelihood of linear drain not being able to handle it all increases, thus likelihood of water going into main part of bathroom increases (if there is no curb or door that will stop it). If you have a recessed center (regular) drain) in your curbless shower, then the recess can be like a shallow bowl that can hold some of that water before it runs out of shower. Hmmm - lots to think about.

Now that we are talking about waterproofing the whole room and sloping up from the door threshold to achieve the needed height, I will jump in with my situation. I had a pre-fab wheelchair accessible shower pan made of solid surface by Transolid. They have the drain on the front edge of the pan. It is a shallow trench covered with a metal grate that meets up with a standard 4" square drain at the center, a couple of inches in from the edge of the pan. All the water flows to the center and the square drain handles it. They also molded a tiny curb just inside of the trench drain that helps direct the water to the center 4" drain, making the trench sort of a back-up. I think the curb is 1/3" to 1/2" high. Because of the possibility of a back-up or other catastrophe with water in this shower, I insisted on a floor drain in the room. My bathroom floor is 8.5' long by 5 ft wide, with the shower being an additional 38" x 63" box along the long edge of that floor. The door is on the short edge, about 38" away from the shower. The door is on the right in this sketch. First, my builder did recess the subfloor to be level with the tops of the joists. He purchased a Shluter sloping shower floor system to go under the tile on the bathroom floor. In order to get the height to slope down to the floor drain, he did have to get a piece of Shluter foam to ramp up from the door threshold. That is the only really noticeable slant in walking on my bathroom floor. The floor drain is about 18" in front of the left leg of the vanity. He water proofed the floor and the walls 5" up using Kerdi. The drain is that tiled square with an open space around it. Over on the shower pan, you can see the square of the shower's central drain. So, my house is protected from anything in this room springing a leak.