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)?

I was definitely worried about hiring a contractor who didn't know what he was doing. I did a fair amount of research so when I spoke with them, I could tell how comfortable they were with the requirements and in our case need to modify the joists below the floor. Some even opening admitted they hadn't done one but were willing to take on the task. No Thanks! I monitored several forums on the web and set up a google alert for "curbless shower" and tried to get a sense of experience. One of the forums is particularly good and turns out one of the contributors was from our metro area. I could read how he communicated and also sense how the other experienced guys on the forum respected him. It was amazing to me how in such a large metro area where we live, how few contractors have much experience with this. From what I can tell, it was rather difficult though since our house has a "pier and beam" foundation, that made it a bit more straightforward. It was also very expensive but the guy I hired is good and he knows he's good so didn't have to low bid the job. (I also liked that his bid didn't change during the job). We have an old house and he personally lived in an old house so was accustomed to the eccentricities and surprises of old houses. Overall, I felt VERY lucky. Maybe in time, contractors will get more experience but for now, it is scary what a risk you are taking hiring someone for this job. If I hadn't had the extra information for this contractor, I might have just chosen one of those "kits" - check out the Schluter web site (linear drains are a bit expensive but worth it) and definitely the forum run by John Bridge. I think a homeowner shouldn't try hiring for this kind of job without doing a lot of research and having a lot of confidence in the contractor they end up hiring. Angies list had a couple of reviews that looked interesting if I hadn't of found the contractor I ended up with. Good luck.

First..do a moisture test on your existing slab. You want to see if moisture vapor is coming up into the basement from under the slab. Tape a 2' square sheet of poly on the floor and see if there is any moisture under it after 48 hours. If the moisture is significant, it might play into what type of membrane you use on the floor. Memebranes like Hydroban and Kerdi have similar properties when it comes to liquid moisture, yet differing properties when it comes to moisture vapor transmission. Significant moisture drive could actually lift and delaminate a topical membrane from the slab. If you have under-slab drainage or radon ventilation pipes, and foundation perimeter footing drains, you should be in fine shape. I'd make it a wet room, pretty much follow Bill's advice; -slope the entire floor to the drain. -topical membrane on the entire floor and up about 6" on all the walls, or just fully membrane all the walls. Fully membrane the shower walls. -ventilation. Don't skimp. This room will be cool and the basement itself is typically humid, so latent drying action will be less than in an upstairs bathroom. Do what you can to eliminate moisture vapor as it is generated. -I'd not insulate or heat the floor. You might have to balance relative humidity in the basement as a whole with a heat source in the bathroom. If you do have vapor drive into your basement, it might help to have something as simple as an IR bulb on a timer to help with the initial drying of the room. For a humid, slow-to-dry shower environment; A non-porous porcelain tile might be better than a porous natural stone tile. An epoxy type of grout might be better than a portland-based grout.

You've apparently thought this out, and you seem to know shower requirements. But just to clarify let me drone on a bit so I know we're on the same page so to speak: There are a few rules for shower construction, you're apparently aware of them but I'll repost for the heck of it: 1) When the shower is complete and with the drain plugged, the shower needs to be able to hold a 2" depth of water over the drain before water flows out of the shower. 2) The waterproof membrane in the shower must be pitched to the drain. 3) The shower floor should be pitched to the drain a minimum of 1/4" per foot and a maximum of 1/2" per foot. "Regardless of whether I use a preformed pan or build a mud bed, doesn't the fact that the entire pan will be lowered 2" below floor grade remove the need to slope the shower 1/2" per foot?" You want a "curbless shower", which means a non-vertical transition at the shower threshold. Meaning at the shower entry there is simply an "angled" transition from the flat bathroom floor to the sloped shower floor. With a 36" by 48" shower with a center drain, the drain will be 18" and 24" from the walls of the shower. To lose 2" of vertical over that short of a distance, you'd have to pitch the floor steeper than the 1/2" per foot maximum pitch allowed by code. That is for a shower with a sloped floor transition at the shower entry, what we refer to as "curbless". If you are willing to have a vertical drop at the shower entry, then you could use a premade pan like the laticrete pan. In general, the pans use a 1/4" per foot slope. The pans will also have a thickness of material at the drain. I don't have a schematic that shows the cross-section thickness of the hydroban pan, so I'll use the equivalent measurements from a Kerdi Tray for illustrative purposes only: Let's say you're going to use the hydroban pan, 36" by 48". The pan will have a thickness at the drain, let's say 1" thick. The longest dimension from the drain to the pan perimeter is 24"; half of the 48" dimension. The minimum shower slope is 1/4" pitch per foot, so the vertical drop over those 24" will be 1/2". Your pan will be 1-1/2" thick at the perimeter, the pan will have a vertical drop from the edge of the pan to the drain of 1/2", and at the drain the pan will be 1" thick. Getting back to the required 2" depth of water requirement: The pan only has a drop of 1/2". For code purposes, you need 2". So the edge of your pan will have to be 1-1/2" below the height of your bathroom subfloor. With the pan having a total thickness of 1-1/2", you'd need to cut down the joists in your shower enough so the top surface of the subfloor within the shower is 3" below the top surface of the subfloor in the bathroom. With the pan installed this way, you'll have a flat bathroom subfloor, then a 1-1/2" vertical drop down into the shower before you hit the edge of the pan, then the pan will slope another 1/2" to the drain. There's your 2" requirement. Made up of 1-1/2" of vertical drop at the shower entry, and 1/2" of pitch across the pan. So while there may be no traditional curb that you have to step up and over to get into the shower, there is a small step down. So by definition it's not what we call "curbless". I hope that makes sense. "With a 36" x 48" shower, I don't see there being the option of keeping a linear drain 48" from shower opening. [Drain placed on the back wall, is the 48" length, putting the drain less than 36" from the opening.] " With no drawing showing your door location, we're simply looking at this from different perspectives. You know your overall design. I don't. The description I wrote would require the entry to be on a 36" dimension of the shower and the linear drain to be 48" from the entry, on the other 36" wall. That 48" run will allow you to pitch the floor 1/2" per foot over a 4' distance for a total of a 2" vertical drop. That's simply one description of how you could get a true curbless shower (with a simple sloped floor transition) using the dimensions you gave. I hope all that helps, at least a little! lol