I have built two curbless showers with in the past year and a half. Both where built using Ditra, Kerdi and Red Guard. I have been having more and more clients ask for trench style drains and have spend about 8 months researching these beauties. Quick Drain USA has a nice channel (trench) drain with excellent tech help and a wonderful website. ACO now imports to North America from the UK and I have found that their drain can fit on top of a Schulter drain rough in (this can not be done without modifying the stock unit and I'm sure it will void any warranty). All that said I should have much more answers to this specific question in roughly 3 months time. The more I look at the trench drains and the more we explore the options it creates it's no wonder the channel drain is the hottest look of any new shower. As far a a nice clean looking curbless shower with a simple Kerdi Drain the entire bathroom needs to be waterproofed. Toilets should not be placed too close to the shower entry because a typical floor mount toilet is the biggest weak link in a wetroom floor. A better option is installing a wall mount toilet or small covered curb (i.e. pony wall, glass block wall, frameless glass on low curb) that separates the toilet location from the wet zone. Make sure you pipe your new curbless with at least a 2" drain line (with properly sized vent line) your design and polumbing package might need a 3" drain line so even though you want the new channel drain you may need to install a standard drain in addition to the floor drain. It's hard to teach an old dog new tricks - Push your builder or tile guy to research harder. Be prepared for extra costs. Framing changes, concrete work and structural engineers may need to be used. I designed my last two around standard framing and raised the transition from the hallway to the bathroom to 3/4" - 1" (Solid hardwood reducer at doorway) and pitched everything back to a single Kerdi drain.

I have never used Kerdi products, but from what I've read in my research, there should be absolutely no problem using a Swanstone base in combination with them. I just have a question for you regarding your tiled bench. Have you sat on/tried a bench that is only 11.5" deep? I have a teak bench that is 12" deep and I just went and butted it up to my tile wall to see what that would feel like. It was quite uncomfortable for me, My back hit the tiled wall and the bench cut into my upper thighs. Now I know I have a big ...., but I would suggest you try it for yourself. I really like the flexibility of having a separate bench. I have used it outside the shower in front of my vanity, and I found I liked to move it more forward in the shower for shaving my legs. Just a thought...

Kerdi Update: I've gotten a couple of emails regarding the newer "Kerdi-DS". First, emails. I often get emails sent to me through the G'web email system, and because of the sender's setting on his/her G'web account, those emails can not be replied to. So don;t think I'm rude for not replying to your question. More often than not, it's literally impossible for me to reply to your email due to your account settings. Kerdi-DS. What is it? It's simply a thicker version of plain ole Kerdi. Kerdi is 8-mil, Kerdi-DS comes in at 20-mils thickness. Why is -DS now getting attention here in North America? Because TCNA has changed their recommendations for membranes used in commercial or heavy use steam showers. Recommendations for residential use steam showers have not changed at all. What or who is TCNA? TCNA is the Tile Council of North America. You might see references to TCNA when it comes to installing tile. TCNA publishes "best practice" guidelines for tile installation. You have an organization like TCNA which is fairly nimble when it comes to changing recommendations for installing tile. Then you have "building code", which only gets updated every few years, and updates are subject to influence from various interest groups; be they trade groups (plumbers, electricians, etc) or large corporations that make building materials. TCNA will often make tile/shower/bath recommendations that improve building practices several years ahead of those changes being implemented into state or national building codes. Blah blah blah. So what is this about? We have water barriers, which limit the penetration of liquid water. Then we have vapor barriers, which limit moisture vapor penetration. At a minimum, a water barrier is needed in a shower or tub surround. A more robust barrier, or a vapor barrier, is needed in a steam shower. Protection from vapor penetration has been typically defined by a product's "perm rating". Previously, if a product had a perm rating of less than 1.0, it was considered a vapor barrier. Example, a topical membrane that I use often is Hydroban. Hydroban has a perm rating greater than 1.0, so it can be used as a waterproof membrane in a shower, but it won't suffice as a vapor barrier in a steam shower. A product like RedGard has a perm rating of less than 1.0, so it can be used as a waterproof barrier in a regular shower, or as a vapor barrier in a steam shower. Kerdi? "Regular" Kerdi, the "standard" 8-mil thick Kerdi, has a perm rating of around .90, so it can be used as a water barrier in a regular shower, or as a vapor barrier in a residential steam shower. TCNA has revised their recommendations for vapor barriers used in heavy use or commercial use steam showers. Health clubs, spas, etc. Whereas the old recommendation was to use a material that simply had a perm rating of less than 1.0, for commercial installations like listed above the recommendation has been...

Being the stubborn guy I am, I'll throw this out one more time... 8^) You want to use a schedule 40 solvent-weld trap under the shower floor, not a threaded trap. See in the above photo how the horizontal drain pipe rides right under the subfloor, but the P-trap itself is low-profile enough to allow the drain to attach without the flange being forced too high? I'm only reinforcing this because I'd hate to see you go to all this effort without knowing that there might be an easier work-a-round. The trap in the photo is made up of a street elbow (the 90 degree piece) and the "U" shaped trap. If needed, you could modify the trap and lower the "U" piece by adding a coupler and a short section of straight pipe between the street elbow and the "U". Anyhow, sorry to belabor the point. Moving on to your follow-up question, the vertical restriction is just 2" from the top of the curb to the top of the drain. There is no "edge of the pan to the top of the curb" requirement. Think of it this way: If your drain were to become plugged up, code requires the pan need to hold 2" of water depth over the drain before water starts cascading out of the wet area and onto the bathroom floor. Code doesn't care if the 2" is part slope and part vertical, all slope, or all vertical. It just wants 2" of water depth over the drain before your bathroom starts flooding. Hey, and thanks for the feedback, I'm glad the Kerdi tutorial was of help! Best, Mongo