A couple of things...you don't need a 2" rise from your shower drain to the back wall of your shower. The floor only needs to pitched 1/4" per foot of run. A 4'6" run would require a 1-1/8" elevation rise, not two inches.

Think of the 2" requirement this way...if you stopped up the shower drain and filled the shower so that there was a 2" depth of water over the drain...will the resulting pool of water be contained in the waterproofed area of the shower or bathroom?

In a typical shower, it's the curb at the shower entry that contains that pool of water within the footprint of the shower.

In a shower depicted as you have, water would flow out in to the bathroom...so without any ther action being taken, you;d need to waterproof the entire bathroom floor, and run the waterproofing up the walls a bit. Plus you'd have to deal with the toilet, etc. It's commonly referred to as a "wet room."

One other item. Some local codes prohibit the trench drain from being at the entry to the shower. Sudsing from shampoo and soap can result in the shower water sheeting right over the trench drain grate and flowing out into the bathroom floor.

I'd run the idea past your code officers. They'll fill you in on details for floor slope and waterproofing requirements.

Thanks mongoct -
So there has to be space for a "pool" somewhere around the drain whether you use a center regular drain or a linear drain.

In the diagram I included above, if the linear drain were recessed to meet the 1/4 inch per foot of run, then it would be okay but that gets us back to seeing that a linear drain requires being recessed just like a regular drain.

So I'm back to thinking that about the only advantage of a linear drain is that it looks nicer, i.e. cosmetic.
Maybe in a case where the shower is huge or the run off huge, the linear drain could handle more runoff but in a standard homeowner shower (even if it is a bit large at 5X5), don't need the extra horsepower of a linear drain.

FYI - we do plan to waterproof the whole floor since room is relatively small and also we have a pier and beam foundation giving us some options to lower the floor and create the "pool". Toilet will be wall mount with floating vanity. I mainly want to make sure I'm not passing up the opportunity to add some serious "sleekness" to our bathroom if I choose a regular standard drain. Doesn't sound like it really, maybe only a little.

elphaba, your diagram doesn't show enough.

if everything is sloped downhill, any slope to any shape (length) of drain *might* work - but in your space everything seems to be open to view so you have only two serious options or so it seems. A drain in the middle of an inverted cone, or a drain that hugs some wall or crosses an opening : right out in the open, like a shower sill but the reverse, a lowering of the floor. In this case, you paint more shower membrane onto more floor area because the entire bathroom is now considered a "Wet room" bathroom .

"Wet room" bathroom are the right words to use for web searches. Keywords.

> So I'm back to thinking that about the only advantage of a linear drain is that it looks nicer

The linear trench drain has several other advantages. If the rest of the bathroom floor slopes toward the drain, you can easily clean the floor with a wet mop and throwing a bucket of water on the floor - everything drains into the trench. If a pipe springs a leak, it won't flood your house because everything will drain. And whilst showering, your feet won't constantly be stepping uncomfortably on a center drain.

"So there has to be space for a "pool" somewhere around the drain whether you use a center regular drain or a linear drain."

Yes. No matter what your design, or what type of drain you install, there are pretty much two basic requirements:

1) the shower floor area needs to be sloped towards the drain at a min pitch of 1/4" per foot and a max of 1/2" per foot.
2) With the drain plugged and with a 2" standing depth of water over the drain, waterproofing needs to contain the pooled water from intruding in to the non-waterproofed areas of the house.

"In the diagram I included above, if the linear drain were recessed to meet the 1/4 inch per foot of run, then it would be okay but that gets us back to seeing that a linear drain requires being recessed just like a regular drain. "

Correct. For your depiction above with no changes to the drain elevation, let's say you install the drain "as is". The floor to the right of the drain that is in the shower would need to pitch to the drain at 1/4" per foot, so the floor tile at the right wall would be elevated 1-1/8" (4.5' times 1/4" per foot) above the drain.

If the bathroom floor to the left of the drain was flat (as it is in the drawing), you'd have to install a 2" vertical curb at the bathroom doorway. Your wall-mounted toilet and vanity protect those items. You'd then have to waterproof the entire floor and run the waterproofing detail up the walls several inches.

Let's say you want to keep your bathroom floor flat with no curb at the bathroom/bedroom door threshold. Here are a couple of examples of how you could account for the required 2" vertical. In new construction they are easy to accomplish, in remodeling maybe not so easy:

1) drop the floor in the shower 2" below the bathroom floor by shaving down or dropping the floor joists. Then reverse the direction of the floor slope in your shower so it slopes down from left-to-right. Your trench drain will now be at the right wall. With your bathroom floor "flat", you'll have a curbless entry at the bathroom/shower floor transition. The shower floor will slope down to the drain at a little under 1/2" per foot of slope, about 7/16th" per foot to achieve the 2" drop over the 4-1/2' or run.

2) Keep the drain where it is in the drawing and the slope as depicted, from right-to-left. Add a 2" curb at the shower entry. Not curbless, but a 2" curb.

3) A hybrid of the two previous examples. Add a 2" step up at the shower door entry, then have the floor slope away from the shower entry towards the right wall, with the trench drain on the right wall. You'll have a 2" step up but then the floor will slope down within the shower.

One note: Even if you did a true curbless like in example #1, I extend waterproofing out of the shower and on to the bathroom floor for several feet. You need to account for not just the physical size of the potential pool of water, but also the wicking and capillary action that will pull water away from the pool.

I think I understand. (The shower will have walls on three sides and partial wall on 4th where the door to the shower will be (and in my drawing, where the linear drain would cross the threshold).

But now thanks to mongo Bill Vincent - I see how this should be reversed with linear drain spanning the wall opposite the door and with walls on either side providing the "pool" needed for the 2 inch drop if I want the main part of the bathroom floor to be flat.
I can see how a linear drain would make for easier navigation within the shower by a wheelchair.

If I choose to use the standard regular drain in the center of the shower rather than a linear drain along the wall in the back, will navigation (i.e. turning around) be difficult for a person in a wheelchair? Given the 2 inch slope down to the center drain designed to be totally within the 5 X 5 space? and with the rest of the bathroom floor flat? (and with the shower still having 3 walls with a fourth partial wall next to the door)?