There are many tile pros who will weigh in on this, but speaking as a homeowner, no, I would not trust the Hardiebacker board alone for a shower installation, with no other waterproofing. (We are currently removing a poor older shower tile installation with tons of mold damage inside the walls, and it's just been a dreadful job to mitigate.)

I know this is a relatively new cement board product, however (I think it came out in 2018 or thereabouts?), and advertises itself specifically as not requiring waterproofing, so your tiler seems to be correct as far as that goes and not misleading you on that. Have they used this specific product before?

If folks here don't know, I'd also check in over at the John Bridge Tile forum and see what the pros there have to say:

https://www.johnbridge.com/vbulletin/forumdisplay.php?f=1

Thank you for your reply! He said that this is the way he’s been doing it since the product came out. He is going to put a Kerdi membrane down on cement floor of shower and has sealed all the seams. The niche is also Kerdi and I thought we were going with Kerdi board for walls, too.

I wish I knew more -- I'd definitely recommend the great folks over at John Bridge's forum for the latest on what tiling pros are experiencing with this new version of Hardieboard. It does seem it would be easier (and easier to warrant) to just use Kerdiboard and keep the installation all in the same brand.

Its not a great product nor approach. Id spend the extra on a true waterproof foam board. GoBoard for example is not much more and far and above smarter.

Thank you guys so much. A special thank you to you, @circuspeanut. You saved me a lot of future money and heartache.

I had read up and informed myself on the approved ways of waterproofing and watched a number of videos and read a few blogs to understand the basic premise of waterproofing. But that website was able to give me concrete and live advice from certified pros.

This person didn’t follow a single part of the instructions for this product. Not one. Even put it directly into the cement board and used it to build the entire shower curb without any plans of sealing the edges. This goes against the highlighted section of the instructions of what NOT to do. would wick moisture and create mold.

The entire thing has to be demoed and restarted. Hiring someone else to do it now.

The Homeowner's Guide to Hiring a Qualified Tile Installer (ceramictilefoundation.org)

Thank you for this guide!!

Hey Julia,

I haven't been around much this month, glad to see you got it resolved with a new contractor, despite the stress that surely caused for you. I love the folks over at the John Bridge forum, they talked me through my first DIY tile job many years ago and I'm pleased to see they've retained a number of the same helpful pros still commenting. :)