I think if you are in NYC and this is a code issue then you really don’t have a choice . I actually like a good actrylic pan it is easy to keep clean and I like it underfoot better than tile .

Do you have suggestions for an acrylic pan? My contractor mentioned a lead pan and then tiling on top (I was asking about his methods for waterproofing since I've seen so many trainwrecks on here!). I am not 100% sure it is code, but will ask him (I just want to formulate all my questions and send in one email).

Here you go Gcubed, NYC building code.

Chapter 27 Plumbing Fixtures

P2709.2 Lining Required

The adjoining walls and floor framing enclosing on-site built-up shower receptors shall be lined with sheet lead, copper or a plastic liner material that complies with ASTM D 4068 or ASTM D 4551. The lining material shall extend not less than 3 inches (76 mm) beyond or around the rough jambs and not less than 3 inches (76 mm) above finished thresholds. Hot mopping shall be permitted in accordance with Section P2709.2.3.

Your contractor said he'd use a lead pan, he didn't say it's all he is allowed to use, right? Here's the code you to read if interested.

https://up.codes/viewer/new_york/ny-residential-code-2010/chapter/27/plumbing-fixtures#27

Thank you @kevin9408. I tried to find this the other day and found one document but it also said there were 3 options. My GC said that for the project I was asking about, he would use a lead pan and that could be covered with tile. He did not say it was the only option. If there is no REAL downside to the lead pan (apparently it is used and up to code), then I'd rather he use something with which he is familiar. I appreciate the links- trying to navigate the DOB website was confusing. Are yo familiar with bathroom renos and NYC in particular? I'd love any advice so i can have an intelligent conversation with GC!

I've tackled about a dozen bathroom renos in my lifetime and not as a professional, and not in NYC. I've seen so called professionals destroy people's bathrooms (and homes) with bad, wrong, lousy, dangerous renovations, and your desire to become proactive and learn is the first step to avoid a nightmare. Code usually is the minimum and not always the best when it comes to shower walls. (from the NYC code)

R702.4.2 Cement, Fiber-Cement and Glass Mat Gypsum Backers

Cement, fiber-cement or glass mat gypsum backers in compliance with ASTM C 1288, C 1325 or C 1178 and installed in accordance with manufacturers' recommendations shall be used as backers for wall tile in tub and shower areas and wall panels in shower areas.

Minimum but not the best, so ask your GC what he will use on the shower walls. If the reply is sheet rock or Green board fire him on the spot. If he states one of the above he's going with minimum, fine but then ask him about a Ditra membrane over the backer. Now you're adding the best water protection for a shower, look it up, it also has many advantages for tile installation besides water proofing. Ditra is also used on the floor if you're going to tile it.

Get to know your codes, one electrical light switch location could but your remodel in limbo even if the switch was there before the remodel but doesn't meet code now. Ask him these things, like lighting, there are codes on damp and wet locations along with location of a ventilation fan, fixture to fixture spacing, ect. If the GC doesn't get the proper permits and inspections there is a chance the city could make you tear out the reno, protect yourself from the nightmares.

A couple of things to read and research. First you said he prefers to use this:

https://laticrete.com/tile-and-stone-installation/waterproofing/9235-waterproofing-membrane

So, you should read the manufacturer's installation instructions. What does he put under this membrane? My tile pro prefers to use laticrete hydroban boards that already have the waterproofing membrane applied to them. But you are correct that you should go with what your tile pro is comfortable with, as long as his whole process follows manufacturer's instructions, local codes, TCNA standards, and there's another one, hmmm (ASNI, something?). Maybe a pro can fill that in. Put that statement in your contract. Find out what else he's going to use under the membrane, and print those instructions also. Find out why he wants to do the lead pan, see if he has experience doing the other types and discuss. Did he do a shower for you in your other apartment? If no, don't assume he is a trained and certified tile pro. Find out. Is he the GC? If so, he needs to hire a certified pro. "I've done lots of showers; never had a call-back" is not an acceptable answer. And if he does hire the tile sub, you need to have a say in who that is by insisting they are trained, certified and experienced. Don't let the GC hire a cheap, unqualified tile "guy." That will increase the GC's margin and harm you.

Here are some sites you can go to to find a trained, certified tile pro:

(I'm sure there are other resources and sites, so maybe a pro on here can add to this list).

https://www.tile-assn.com

www.ceramictilefoundation.org

You can read the bathroom sections of the TCNA manual by buying a downloadable version for about $40:

www.tcnatile.com/products-and-services/publications.html

The only YouTube videos I recommend are from Sal Diblasi. Stop there though; don't go down a rabbit hole of online misinformation.

Here's also what I did when I was searching for a tile pro. I called everyone who was recommended to me, I called tile shops, and I asked 1 simple question: "How do you build and waterproof a shower?" You would not believe the answers I got.

"You put the drywall up, and put the tile on that. The tile is waterproof."

"You don't need waterproofing as long as your careful not to splash."

"You don't need waterproofing because you have central air conditioning; that'll pull all the moisture out."

So, ask your contractor that simple question. Write down the steps and materials he says he would use. Then post his a answer here.

Edited to add: Ask him how and where he learned how to waterproof and tile a shower. Is he certified by any tile association? Does he go to trainings to keep his skills up to date? Does he meet with the local reps from Laticrete and other companies to get sample products to try out and keep learning what's available? Does he train others? My pro does all of that stuff and more. That's the kind of person you need. I had one of these HOUZZ horror shows you refer to because I hired badly. Before hiring again to re-do it, I did all the research I just listed above so that I could ask better questions and make a better hiring decision.

Once again, @kevin9408, thank you. Contractor mentioned laticrete 9235 as the waterproofing. I'm not sure where that falls in the layers of stuff needed. We have been happy with this contractor (for price, efficiency, etc) so hoping we can work with him for the bathroom vs finding someone new. He says purely re-tiling (no plumbing/electrical changes at all) should't require a permit. BUT, I think our coop will not agree- and not sure if switching from tub to shower is still considered simply re-tiling even if we keep the shower system the same (or just buy new ones but keep plumbing as is).

Switching from a tub to a shower requires new plumbing behind the walls and a new larger drain below the floor. All old bathrooms need electrical upgrades. You need permits for any of that.

I would never use anyone who does a lead or copper pan.

Thanks, @User. It's not an "old" bathroom per se (meaning, it's not original). I just don't know if it was 5, 7, 10, or 15 years ago. There are only 2 lights switches (one for overheads/over mirror lights and one for shower fan/light). Only one outlet (there is only 1 wall over 4').

What pan do you prefer? I can ask about the other types of course. I know someone who used same contractor for their bathroom 2 years ago, so I can check in with him too.

It's been 5 days. Did you research or read any of the sites and resources I recommended?

I read all these resources in about 48 hours.

Re-tiling is not just re-tiling. It's rebuilding and waterproofing a new shower. You need to do your research. Don't assume this guy is the right one for the job. Hire carefully after you've done you research.

If you don't research for yourself, you might end up being one of the tile horror shows you see here on HOUZZ. You need to educate yourself.

No permit he said? Hum, well in my neck of the woods a permit would be required pulling out the bathtub and setting in a shower. When a contractor tells you a permit isn't needed a HUGE red warning flag should pop up! If you live on an upper floor and your shower leaks into a lower unit you may be responsible for the damages and insurance may not cover it, who knows. You better read the certificates of incorporation, by-laws and House Rules, and since its a a co-op you're not the owner of the unit, but a tenant shareholder under a proprietary lease so read up. Another thing to worry about is someone snitching on you because every co-op, condo and association has a group of busybodies with nothing better to do except watch other people and complain. If you get busted the least the city may impose is a fine or double the building permit fee, but they could also make you rip out the shower because it wasn't inspected, it does happen. I'm not trying to scare you, just giving you a reason to do some research, like reading your insurance policy.

I could be wrong, maybe he can do the work without a permit. Below is a guide line of plumbing work that can be done without a permit in NYC, followed by the detailed administrative code clarifying what work is exempt from permits in NYC for most trades. Have your GC show you the sections which apply to your project.

https://www1.nyc.gov/site/buildings/homeowner/project-requirements-owner-plumbing.page

https://www1.nyc.gov/assets/buildings/apps/pdf_viewer/viewer.html?file=2014CC_AC_Chapter1_Administration.pdf&section=conscode_2014

We've basically only covered one tip before hiring a contractor, below are the rest and you should also read 2 - 13.

13 tips for hiring a contractor.

Huge red flags here. You need to read more, then hire better. It can be done. Go back to those resources I posted.

Thank you everyone (I am not ignoring your advice). I am probably not explaining myself great and I know my GC has done many bathroom and kitchen remodels in NYC; I emailed him off the cuff to get a sense of his cost and perhaps his reply didn't meet my design ideas. He also added a wall in our apartment (with electrical- lighting) and yes, metal framing is what had to be used. I have no issue applying for proper permits; our coop board is very strict so I know they will need everything. I was hoping not to have to deal with an architect/engineer but may have to with the permits (it was annoying to deal with architect for our wall build since I designed it). I did read the NYC code link; the spacing of our fixtures is in compliance so the switch from tub to shower should not cause a problem with minimum distances. I do not HAVE to use our GC though we did have good experience with him. I can ask around about others who have done bathroom renovations in our building. It takes weeks/months to get coop approval (and avoid too many back and forths) and then permits, etc, etc so I am gathering my info for a 2021 project.