Hardibacker against a drywall/firewall

Question

I've read through hardibacker instructions but I'm still unclear on how to install in my bathroom.

I live in a townhouse and my shower is against one of the firewalls. The firewall, it turns out, is just two pieces of drywall put together with no other spacing between them. I presume, based on when I was tearing out the old tile, that there is a stud. However, I'm not as sure of this since I see no screws or nails on the now exposed firewall.

My initial plan was to screw the hardibacker into the same area where there are existing nail holes. But as I think about how heavy the hardibacker board is, I'm guessing the board will just fall off in a manner of months.

How should I proceed? What was there before was just another piece of drywall.

Here's a picture: https://i.imgur.com/RGNcqTR.jpg

Answer 1

If you attach to the studs with screws it will last a lifetime.

I have opted out of HardiBacker or Durock in favor of DensShield drywall by Georgia Pacific.

DensShield comes in different thicknesses so you could match the thickness of what you removed.

You would then screw it to the wall through the existing drywall along the stud lines. Then coat joints with RedGard or equivalent. Then attach your tile with thin set. DensShield is vinyl coated and seals out moisture except for the joints that must be sealed.

Good luck!