It won't work...code requires the shower door threshold to be 2" higher than the drain opening...with a 1/4"/ft slope the minimum distance from drain opening to the door is 8ft and your shower is only 4ft

Briefly...you can keep your slope requirement within the shower footprint if you use a trench drain on the back wall of the shower, 48" from the opening. Up your slope to 1/2" per foot.

That takes you away from a preformed pan, but the single slope and single plane of the floor makes it easier to do a mud bed. Or used a manufactured sloped tray if you still want a manufactured slope and you can dicker with upping the slope to 1/2" per foot as you see fit. Your choice.

I'd do Durock over the studs and Hydroban on the walls behind the corrugated panels. Carry the Hydroban membrane onto the sloped floor surface and down to the drain.

Since I'm recommending a trench drain, look at Laticrete's drains.

They have manufactured sloped ramps too. But again, they are 1/4" per foot. You could pitch your subfloor at 1/4" per foot then install the ramps over that. Cut the existing joists down, then sister sloped joists to the cut down joists. Decisions, decisions.

The Laticrete drain with Hydroban ramp and Hydroban membrane keeps you within a single-family supply chain. Good for material compatibility.

Not sure what your fastening schedule will be for the corrugated panels, or even how they will be fastened to the walls. But you could consider skinning the shower walls with plywood. Then cement board. Then Hydroban. The ply would give you something to screw the corrugated panels in to, instead of hoping that the studs end up where you need them to be.

Realize that will thicken your wall. Take that into consideration when you choose and place your plumbing, especially your shower valve and the valve's trim kit.

Lazypup,

Thank you for your reply.

I plan to lower the shower pan 2" below floor grade, so one steps down into the shower. This would put the top of the drain lower than 2" from the curbless shower opening.

Mongo - Appreciate your helpful considerations. Thank you.

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?

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.]

Wouldn't a Laticrete pre-slope pan [w/center drain] work? With joist modifications, highest level of the pan is 2" lower than floor grade, and from there, lowering 1/4" per foot to the drain.

Fasteners for corrugated panels will be hex head, washer and grommet screws - same as are used to fasten these panels as roofing.

If I leave the 3/4" T&G wall boards in place, they would accept the panel screws.

Again, I much appreciate the help. Please keep the considerations/suggestions coming.

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

I would like to ask the same question, many apologies to dazilazi for the hijack. We are building a home in North Reading MA and I would really like to put a curbless shower in the first floor guestroom (to be used by aging parents) and in the master (because someday we might be old, and it looks wonderful!). I've attached the floorplans of both bathrooms. In the master we have flipped the location of the door to the bathroom and the shower so that you walk into the middle of the room. They are just finishing up framing of the house and the plumbing has not started yet. Our builder hasn't put in curbless showers before. I was picturing putting a built-in bench in the master shower but not the guest. Is a curbless shower possible in either location? If so, does it require a linear drain? Is is a lot more expensive to install a curbless shower if you don't use a linear drain?
Thank you mongoct for your time if you have a chance!