With a curbless shower, I see two issues you may be facing. If he is planning on using a traditional rubber liner, a pre-slope under the liner is required. This slope is a minimum if 1/4" per foot from the drain to the farthest wall. In this case, I assume that to be the entry. I fugure that to be about 2 3/4" higher at the entry than at the drain. The rubber or vinyl liner sits on this and a FINAL mudbed is then formed over the liner. As you can see, there will be issues with no curb and how you'll terminate the slope to a feather edge at the entry. I don't see how that can be done. The other issue is with the liner itself. I see no way to attach it to a mudbed that would have to end at a feather edge. These liners are designed to go UP the vertical walls about 6-8" and nailed into place. Having built these before, scrap the liner and use the Kerdi. It's a bulletproof install, you only need ONE mudbed as the material is bonded directly to the mud and you can generally extend the Kerdi six or eight inches into the bathroom for a bit more insurance. On one hand, yes...it's a bit more cost, but realistically, it's also a shower you'll probably never need to repair or replace. The Kerdi is under $1.40 sq/ft. Their drain will run about a hundred bucks. On the other hand, you only have the cost of one mudbed, you eleminate the vinyl liner, as Kerdi is completely waterproof, you can save by using standard drywall in the shower as opposed to cement board. This is what Schluter recommends. Bottom line is that you'll pay a little more but get a far superior shower. If your tile installer isn't comfortable or familiar with Kerdi, find one that is. Here is a link that might be useful: Kerdi Shower Handbook

Here is the "standard technique", courtesy of Harry Dunbar. There can certainly be slight variations in methods. Example, unlike Harry, I don't use an admix in deck mud. Note the cement board on the walls. There are no fasteners in the bottom 8-10" of the cement board, if there were those fasteners would go through the membrane that was turned up the walls, creating holes in the membrane. The bottom edge of the cement board will not "flop around" because the bottom edge will be locked in place against the wall studs when he packs in the deck mud for the preslope. Note his curb. There are no fasteners on the inside face of the curb or on the top of the curb. Only on the outside face. If your installer perforated the membrane by screwing through the top and inside of the curb, did he also screw the bottom edge of the cement board to the studs, creating holes in the membrane there too? The beauty of the inverted "U" of lathe that is set over the curb is that the lathe ties the mud on all three faces of the curb together, giving strength to the tile and grout that will cover the three sides of the curb. Smearing a veneer of mud over the membrane on the inside face of the curb, tiling over that, and hoping it doesn't delaminate or that the grout doesn't crack over time? I don't have confidence in your man's methods. It's discomforting that he so casually discounts and disregards the proper way to do things. Good luck. I do hope you get things done to your satisfaction.

thank you both for your helpful comments! the plumber will not be doing the tile job as i already have a tile guy who is doing not just the 2 showers but also the floors in the bathrooms (which also had to be ripped out). i only mentioned the tile to show how eager the plumber seems to do any and all jobs, even if they may not be entirely suited to his trade. he does have plumbing and mechanical licenses. so i was just a little bit unsure if shower pan jobs fell under the purview of plumber or tiler because i'm new to all of this remodeling/house stuff. it seems that because it's a drainage issue, the plumber would be the right person to do it, but then there's the mudding part, which seems more of a tile guy's job. i'm almost obsessively concerned with the shower pan liners because we had a leak in our rental house, and it was a nightmare, and i've heard so many horror stories of botched shower pan jobs. sorry, i tend to ramble in the mornings... i'm off to read the John Bridge Forum. thanks again!

I installed my solid surface shower walls over drywall, not even greenboard, and put the custom solid surface pan over the wood subfloor. If you leave an 1/8" between wall corners and pump them full of color matched silicone, it allows for panel movement without leaking. Another of the advantages of solid surface in the shower, besides lack of grout to maintain, is the labor and material savings of waterproofing. Plus the foolproofery.