You need a 2" minimum from the top of the drain to the top of the curb, or lip of the entry floor. If it's on slab, you'll have to bust out some concrete to lower it. If it's Post & beam or 2nd floor, you'll have to remove/lower the floor joists to get the required "fall."

Unless wheelchair bound, I generally just make the curb outta bricks....not a very high curb and a LOT less labor intensive.

Thanks Tech. This is (will be) a first floor addition on a crawl space. I believe the architect has already specced out the (please excuse my lack of terminology here) necessary low subfloor for a curbless tiled shower. But nothing is built yet so we are able to make some changes.

I'm just having second thoughts about the tiled floor. In the past my family has had better luck keeping up a smooth shower floor than tiled and I don't imagine anyone changing. :)

No need for wheel in access--it's not going to be big enough for that no matter how flat it is!

If you are building this you can drop the joists under the shower pan. I wouldn't go much lower than having the shower floor be Level with the main floor. (Normal installation would put it higher than the main floor.

People seem to be accustomed to stepping slightly up Into a bath or shower and slightly down on the way out, but reversing this could cause some issues particularly for the older guest. But putting it level will lower the curb on the room side a bit which would be helpful.

Make sure that you can Get a cast iron shower pan in the dimensions you want, before you finalize your plans. Your options are limited. If you would be interested in solid surface there is a place near me that will make custom solid surface shower pans. That could be another option.

I have the same question. I'm looking at shower bases for a 36x48" stall shower. It seems that most of the shower bases I've found are acrylic.

Kohler makes cast iron shower bases, but the curb is 4-5 inches high. Swanstone makes solid surface shower bases - I think these have a 5 inch curb as well.

I'm thinking about using a Wet Style shower receptacle - this is made from a composite material (soy and mineral based) and has a 1.5" curb.

Here is a link that might be useful: Wet Style Shower Base

We put in a low profile solid surface shower base made by a company in Kansas that our GC recommended. I think they have dealers in most states. We didn't want the upkeep of a tile floor, but do have subway tile walls. It blends very well.
It was installed 3-4 years ago and we are well pleased-still looks like new. It is so easy to keep clean and I love the low profile, so easy to get in and out of. If interested you can google their web-site. The company and product name is Onyx. (I have no affiliation with this company)

Thanks all. This has been very helpful! I'm *that* close to just dropping in a bath tub and calling it quits, but I really shouldn't. :)

I'm taking notes!

I would highly recommend the Onyx Collection shower pan! Extremely easy to install, clean, and has a threshold of about 1 1/2" tall off the subfloor. So after your tail is installed up to it you will be looking at about 3/4" tall. Check out the link below for more info.

Here is a link that might be useful: Onyx Collection Shower pan

lizbeth-gardener, are you by chance in the buckeye state?

I have a kohler cast iron shower pan. It is not more than 3" above my finished tile floor. I love it, but I love cast iron. I think that if your guest can walk, they can step over a curb. Walking requires lifting the feet up at least that far I would imagine. I have French doors on my shower in the event a wheel chair needed to go in there. I see no problem getting a wheel chair over a 3" curb. I've taken W/C over larger obstacles. I thing even more important will be strategically placed grab bars. One for use getting into the shower space, and another for use inside the shower on the surrounding walls. The shower head holder bar can be a grab bar too. If you look around you'll find them available.

Thanks, Enduring. Sure looks nice; I especially love that meganiche!

Fori, I liked it too, at least the concept of it. I didn't get to put it on the wall where the shower controls are so I had the carpenter install this big niche. But I would not do it again because when I wipe the shower down I have to remove everything from the shelf to wipe it too. So now I end up keeping every thing on a little plastic folding foot stool on the floor :( I have been looking for a narrow chrome or plastic tote for that space. One that I can load my bottles into and when it comes time to wipe the shelf down I just pick the works up and wipe, then put back. I don't have that many bottles so how I work now is ok. Just wished wiping down the shower wasn't part of my shower experience.