You will need 1/4" per foot slope to get the proper run for the water to go down the drain. with a 4' shower, if you choose a center drain, that means a center drain has to be a half inch lower than the shower door (and walls) 2' away if you you are going to do curbless. That means that you have to either build up the rest of the room's floor by 1/2" and have that be a lip at the bath entry way, or you have to find a way to recess that drain downward that 1/2". If you are on slab, that means chipping away at the slab with precision and if you are on crawlspace, that means trimming the floor joists. Neither is easy, and in the case of trimming the floor joists, it's not even advisable to do without an engineer's report.

Take that same bath and put a linear drain at the entry to the shower and that rise needed to get the water to run becomes a full inch of buildup at the far wall of the shower. It's pretty easy to add an extra 1" of mud to any existing surface against a wall than it is to try to create a bowl. That just leaves the actual trench for the trench drain to be chipped into the concrete or fitted in between (hopefully) the joists. If you have to cross the joists to fit in the drain, then you're back to increasing the degree of difficulty and needing a structural engineer to deal with the joist alteration or support.

Either way you choose, don't forget to do full blocking behind the walls of the shower so that support bars can be installed wherever needed in the future.

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.

it is possible to use a linear drain in another configuration, which makes a bowl/container for shower water. The walls are part of it. Behind the walls is a continuous membrane, so nothing to worry about.

With a center drain, one is not required to use mosaic tiles. Any four triangles can fit together to meet in the middle, and these triangles are sloped to the drain too! Any large size tiles will fit on each of these triangles. The joint line between each pair of the four triangles will be visible as a grout line. No big deal.

Hth

davidro1 - thanks for the explanation about the triangles. I see where that config might work. (and I know about the membrane which we plan to use in any config we end up with.) But I AM wondering why some may promote use of smaller 2X2 mosaic tiles to ensure strength/stability, i.e. no chance of cracking/breaking (wheelchairs riding over??)

But also wanted to confirm what I think now about a possible linear drain and whether it likely "meets code". I'm in Texas.

I've tried to make diagram below reflect a 2 inch rise within the shower from wall to wall (in a case where there is no center drain). Sorry if it is hard to see. Hopefully, the general idea is apparent. (Shower will have 3 tiled floor to ceiling walls with 4th wall that includes shower opening (no door) and next to door on same wall will be glass wall adjacent to vanity.)

Looks like linear drain will need to be sized carefully to manage "run off" but technically, are curbless showers built this way (very often)? Would this be wise?

I don't want to overkill if I don't have to with a secondary drain but honestly, this setup I've drawn below seems risky to my non-professional homeowner brain.

And I'm still exploring options with option for regular drain still looking good though the "sleekness" of the linear drain is definitely appealing.

Feedback, anyone?

Thanks davidro - makes sense.

small tiles gives some tile installers more room for "error". Your thinset and your mud pan might not all be perfectly geometrical.

I don't know where you guys are getting that 1" from. The code says the top of the threshold at the door MUST BE 2" higher than the finished elevation of the drain opening.

Code also limits the pitch to a minimum of 1/4" per ft and a maximum of 1/2" per foot.

To have a curbless door even with the maximum 1/2" per foot pitch you need a 4' run from the door to the drain opening.