I would buy a free standing shower bench/seat.

Not built in.

Thank you for your response. I want the built in bench for stability as I age and will need to sit to shower. I am also installing grab bars once I settle on built in seat location.

When we built our current house I skipped built-in benches for flexibility when ageing. I used teak benches from DecoTeak. They offer different styles, sizes, and heights. More ergonomic to sit on, and never cold and hard.

I would also skip a tiled bench as they are always cold. (They seem like a good idea). If you feel like you are building an age in place situation a free standing bench is much more flexible for you and a caregiver. If you insist on a tiled bench do it on a 45° angle in the corner

I now have 3 comments that suggest skipping a built in bench for a movable one, I guess I may need to rethink this? Does anyone else have an opinion on built in for aging safety?

My advice get a walkin tub and shower if aging in place is the idea. If you get to be so infirm you cannot walk to the shower then you will need room to have a walker to sit in when you shower so just do the walkin tub with shower . I am 78 yrs old still get in and out of a regular tub so I think when the time comes a walkin tub will be my choice since I love my bath tub every night/ I think if aging in place is the plan get some real help with even placement of grab bars , that is a big shower maybe 2 shower heads might be needed too. It will aslo need to be designed with no curb so all water proofed for the whole floor .

No clue your age, but if planning to be carried out of your home feet first?: )

(Note:)

Safety and stability is but ONE aspect of aging.

The rest is usually a dream that fails to happen for reasons too numerous to list. Bathrooms can be the least of the ISSUES, and far beyond benches and grab bars.

Nobody start screaming, it is just fact.

If you're not already annoyed? Post the entire plan. The graph paper concept is fine: )

Every wall, window , opening and where those opening shall lead.

Not a fan of built in benches but if you must:

Make it deeper than 14" ( not sure the size of your cheeks but that comfort will be critical). The bench should position in case you need assistance. There needs to be a handheld faucet close by with a mounting bracket so you can have a seated shower. The water from that should not angle at the shower door ( they are not water tight ) . Grab bars in appropriate locations - not just one.

For aging in place, this is probably why most people are recommending a moveable bench. That is what I will be doing in my own shower.

Good luck

For aging in place, seems zero entry and no door should be in play for such a big shower. That bench is huge. I will leave that to experts. If putting in the bench, should be waterfall rather than drainage underneath. Experts weigh in but I did not do that and I regret it as it never dries underneath and a pain to clean on my knees. Live and learn.

Thank you all for the experienced answers. No built in seat