If you're writing about extending the concrete "floor" into the shower as your "bare" shower floor, I'd advise you to rethink that. It could turn into mess over time, not just affecting the shower floor, but with moisture eventually wicking out and saturating portions of the bathroom floor too. Now you can certainly do anything. If building code applies in your area and you want to be code compliant, it does make it a bit more difficult to have a code compliant "naked" concrete slab in a wet room bath and shower. To be code compliant, believe it or not it's probably less expensive to tile the bathroom. Pour your slab. If you want to use large format tile you need a flat slab, one flat to a certain specification. You'll have to spec it out to the concrete crew IN YOUR CONTRACT and verbally, it needs emphasis. Realize that the larger tile you use, the flatter the floor has to be. Once the slab is in and is sufficiently cured, you can apply a topical waterproofing membrane right on the slab, then tile right on the membrane. There are modern/industrial looking large format tiles that sort of look like concrete. Or if you go with another shade or hue, they'll blend well into that style of bathroom. Here's a 12" by 24" charcoal for example, they also come in 24" squares. If you want to extend the large format into the shower space too, I'd recommend looking at using a trench drain. That way your shower floor can be a single-plane, flat surface, that slopes to the trench drain. You'll not have to cut your large format to fit the inverted pyramid shape of a typical shower with a center-floor drain. Trench drain example:

Creative Tile Eastern CT: I can see that a custom shower base and such can be done for less money than a purchased base. For whatever reason, the details of a custom base seem to be problematic for a lot of people. There are multiple posts here of bad shower jobs - where they leak, the water doesn't drain correctly, etc. I know that an experienced person could do this and do it correctly. But I'd rather pay the money for the base and get that part, at least, right. There are other parts of that Tile Redi system that bother me: As a general practice you don't rely on caulk (even 100% silicone) to make something waterproof. The flashing shouldn't be an option where the wallboard meets the base. Likewise I don't like how the "Tile Redi Niche" product is flashed. The flashing around the product routes water to inside the wall instead of to the outside. It depends on caulk in order to keep the water from going inside the wall. The base of the product should be flashed to move water to the outside. The sides should also have flashing on the outside IMO.

Thanks for your response! I assume that our plans did (though I'm not sure) and our plans were certainly approved so I don't understand whats happening here at all. My contractor is equally perplexed and says he's never heard of this type of installation nor of this being required. The wall in question isn't a shared wall, the other side of it is the exterior of our unit. We also had a permit from the beginning. For some more color on why things have taken so long: a good 7-8 weeks passed with no work being done because our property management company and HOA kept asking for additional documentation in order to approve the addition of a skylight AFTER the HOA president initially told us that she consulted the management and that we were in the clear to include the skylight in our plans (which we did and we began demo. When it was time to make the hole in the ceiling we reached out because we had a question about something and THAT was when they suddenly had a problem with it). The president AND the property manager were flakey, they'd take days to weeks to respond to our calls/emails and after requesting one thing, they'd come back a week later requesting something else, multiple times. It was ridiculous. We've also probably lost a total of 4 weeks due to various materials we needed on back-order. A couple more weeks lost to poor scheduling of workers by our contractor. His father who lives abroad also passed away during this job so he went away for 3 weeks and practically nothing got done while he was gone. The rest was BS from the city like this. I can't even begin to tell you the shenanigans we've had to go through with the city...waiting a week or two for an inspector to come only to have the inspector ding us for something that wasn't mentioned the previous time, etc. Oh and I forgot to mention the work was only for our master bath/closet and the guest bath (we only have 2 bathrooms total) and we've been living in the unit this whole time so work on both concurrently wasn't an option. Some luck we have, eh?

Are these actually the thin peel and stick tiles or are they older vinyl tiles which are glued down? My friend had peel and stick in her kitchen and literally a Bissel steam mop provided enough heat to melt whatever was holding the tiles down. In fact, she had used the steam mop to clean the floors which is when they started coming undone and she decided to replace. There are lots of places that sell retro looking tiles but it would be almost impossible to find tiles that would match whatever is now on the floor even if portions could be salvaged.