It may have to do with the drain lines under your slab !

The shower drain can't be lower than your waste line , and you are lowering the drain for a curbless spdesign.

Xedos, thanks for your response! Since most of the slab will be removed to move some of the plumbing and the current drain to a new location, it will need to be poured again. When they pour the new concrete, would it be possible for them to pour the floor a little thicker and higher than before and keep the drain at the level where it is now so that the slope requirements can be met?

You can build anything. The question is, can you build it cost-effectively? It sounds like your contractor may be afraid he can't charge you enough to make this worth his while. Talk to him.

"There is nothing that my skills and your money can't accomplish"

Since you're pouring a new slab, I don't see any reason why they can't drop the concrete a few inches in the shower area so you can go curbless. Your contractors unwillingness could be what Joseph mentioned or that he and his guys just lack the expertise.

One thing to be aware of in a bathroom your size is that you will still need a door for your shower. Some people like to be able to go doorless for such a shower, but you definitely lack the space to accomplish that.

remember to tie the shower waterproofing into the main floor outside the shower

Ours is curbless and doorless. It's slightly bigger because there is a tub past the shower. The shower is 36 x 60. The slab was dropped as shown above and a linear drain installed on the far wall of the shower. A tiny amount of water sprays on the bath mat at the shower entry, but not enough to be bothersome. (I was also told it couldn't be done.) PM me and I'll send a photo.

Thanks everyone for your helpful posts! Apologies for my absence. Our modem went out and we finally made it to our internet provider for a replacement. For some reason I couldn't post back to the forum on my cell?? At any rate, my internet access is back!

I talked to our contractor again and asked if we could drop the slab or raise it when they pour the concrete slab. He said he will talk to our tile guy to see about raising the floor when it is replaced since so much of it will be removed during the process. I also mentioned making sure the waterproofing is extended to the main floor and he said they would definitely do that if we do end up going curbless. I'm ok with putting in a glass door and a partition to keep the water in. I should hear an answer back from them soon whether they can do it and any extra costs that we will incur. The cost of removing so much concrete and replacing it was already
included in our quoted price. We are switching the location of the toilet and the sink because the
toilet was directly in front of the door. We expanded the bathroom and are going
from a pedestal sink to a 60" vanity with double sinks. Also, the shower
drain is being moved over since the bathroom has been expanded.

Having the information from you all has helped greatly.

Jerzeegirl, love your shower. The row of black tiles on the bottom is a nice touch!

Lori_inthenw_gw, I will PM you for a photo. Thanks for the info about the shower spray. I would be ok with that if I can do away with the curb.

I guess I'm not 100% clear on your layout. I tried drawing it to scale the way I was assuming you'd planned it, but when I used a 5 foot vanity, I couldn't make it work. I drew it with a 4 ft wide shower at the end so you could get in the 2 inch drop required by code, using a half inch slope per foot. That left 6 ft of depth for the toilet and vanity, but that doesn't work with a 5 ft vanity!

If you use a narrower shower, you do have to start the slope farther back into the bathroom, which would put your toilet on a sloped floor. Unless I'm understanding the geometry wrong! Personally, I'd go with a single sink and more storage, anyway, but we rarely use the sink at the same time.

@acprom
What did you wind up with? Could you share a photo?

@LE would like to see a photo of yours too!