I would be very skeptical and definitely get it in writing. Of course if he is gone next year your warranty is worthless, and even if he is around try and collect on it.

It looks beautiful but....

If you decide to take his word and get it in writing - I can not stress enough if you see any grout cracking / separating, squishy tiles, any black moldy grout only weeks or months after it was built - stop and call them back in immediately. I've experienced way too much new construction leaky tile shower drama in the past and I never wish that on anyone.

We moved in July 2014 and it leaked Jan 2015 - the builder dilly dallied around for 4 months trying to fix it (one of the fixes was to get us a solid surface curb since our was initially tile), until we said enough is enough and asked they just re-build our whole shower - shower was rebuilt in 4/2015 and started leaking again in Dec 2015. Were still dealing with the fall out of it - but things are wrapping up with our newest contractor.

If there is the tiniest part that is not protected I can guarantee the water will find it and you will be in trouble, this builder sounds like he already knows he won’t be around next year so he doesnt care

No, it will most probably not show within one year. If there is no membrane where water will be present, you will have problems down the line.

water does get on the curb/ledge. I wouldn't be comfortable with this..water can cause so much damage over time

"His main argument is that water will not get into that spot, and therefore it will not leak. "

With reasoning like that I would be more likely to doubt he did the rest of the work correctly as that is pure BS. Right is right and wrong is wrong. Will there be water in the shower, YES, is there waterproofing there, NO. He is wrong, fix it or give you all your money back. Do not settle for less than that.

Not acceptable in my opinion but ultimately the decision is yours. How will you know if it fails in two years? What if the damage doesn't "appear" for two years and a week but has been leaking the entire time? Will he honor the warranty? He messed up why should it concern you if it costs him a new liner, his lesson will be learned, no?

Looks awesome, hope everything turns out ok

if he damages the Kerdi, could he replace the curb portion w/cement board painted w/redgard? That is another option. You could always opt for a solid piece curb instead of tile. grout is not waterproof. Even with sealer.

Some designs allow grout to weep as part of a "system", so have to know the whole deal here to make sure.

It would be cheaper and safer for him to redo the shower glass, and get yourself a complementary solid surface for curb top and knee wall. Glass is a redo in that scenario..... or it's all higher by the amount of thickness of solid surface. : ) and the glass guy is skillful

I would not accept this work. I'd demand he re-do it. Water can do unbelievable damage long after 1 or even 2 years. Especially if you live in a humid climate. You risk getting mold and rot.

I have a set up similar to this and have lived here 9 years, and absolutely no problems. But I do squeegee down the glass and tile inside along that frameless glass side. So, you might want to put that in your routine!