would there be ADA regs on that somewhere online?

Minimum door width for a wheelchair is 32 inches...also an occupational therapist friend of mine advises against a built in bench. When she does home studies she says invariably benches are at the wrong height or not in the right location to make transfering from a wheelchair to a bench possible. Something you might want to think about.

That said, a shower chair would only require between 17 and 22 inches, depending on the model you buy. You would transfer to the shower chair outside of the shower and be wheeled into the shower. That would make your opening sufficient.

So if you want to transfer directly from your wheelchair to the built in bench, your current design is problematic.

Thanks for the replies! Yes, there is an ADA limit. I think it is 2 to 2.5" drop into shower, I just want it to be less without sacrificing good drainage.

Cordovamom- thanks for the idea about the shower chair. I will do some research on that. The bench is for now, and for husband. His domain and watercloset are on the other side of the shower.

I'm no expert in these matters, but my husband is recently disabled due to illness and we travel a lot. Most roll-in showers in hotels are absolutely terrible, they tend to let water spread all over the place. You have to create a dam using extra towels to keep water from getting all over the floor.

Your concept of a doorway quite a distance from the shower head is a good one. Yes, you want a handheld shower at an appropriate height for seated use, but where will the diverter be? Be sure all the controls (on/off, temp., and diverter) are reachable from a seated position.

Don't forget properly mounted (with blocking behind) grab bars. My husband finds the vertically mounted ones in his shower to be very helpful when he enters/exits, but he can stand.

It would be helpful if you physically go through the motions of using the shower from a wheelchair as you're in the planning phase. There are many online websites with information about ADA requirements and general hints about building accessible bathrooms.

Fully agree about having a removable bench versus a tiled-in built-in in an accessible shower. At a later date once use is figured out, you could add a folding wall bench.

There are also roll-over collapsible dams for wheelchairs.

Talk to your building department if this will be a permitted and inspected installation. For the most part, residential isn't bound to accessibility standards, but you do want to tweak your design towards it. See what ideas your inspector has about your design prior to starting construction.

A 1" to 1-1/2" vertical drop into the shower is significant for being in a chair. Ideally you're looking for 1/4" to 1/2" max. Code generally requires 2" vertical between the top of the drain and the top of the curb. Code also specifies a minimum floor slope in the shower of 1/4" per foot and a maximum of 1/2" per foot. So you have wiggle room in terms of vertical curb drop plus slope drop to get the 2".

There are basic design guidelines available online. Your building department may have a packet for you too.

When you are done showering, carefully set your footing and rise from the chair, before exiting, steady yourself. Use the chair for support if necessary. Use any handrails available to safely exit the tub or shower. Towelling off in the shower may be the best option. Once you've exited the shower, have someone else remove the shower chair if it does not stay in that location. It should be allowed to dry before storage.

Here is a link that might be useful: Shower chair