Tile-Over-Tile Waterproofing

[Philip.I]

I’m renovating a shower stall. I removed all walls and plan to replace them with waterproof Hardiebacker. But I’m wondering if I can reuse the old floor doing tile-over-tile. The existing pan is over Chloraloy 240, and the tile is solidly in place without cracking. My concern is establishing a waterproof seem between the new backer board and the shower floor.

Assuming I prime with EcoPrim Grip, can I use Schluter seem tape to join the existing tile to the boards? I’m concerned about gaps from the grout lines. Or is there another option that’s better?

My other option is to rip it all out, but I’d have to reroute the shower drain to accommodate a prefab pan.

 

[CENTRALFL]

Just to make sure, when you say "waterproof Hardiebacker" you mean you're going to put plastic behind it and tie it into the PVC liner? Or were you going to use a surface liner on top of the Hardie backer? Hardiebacker by itself is not waterproof.

 

[Sponsor]

 

[Chucky_ott]

LoL, I was going to say the exact same thing yesterday but figured I'd Google it before responding. Turns out Hardie has a product called Hardibacker with HydroDefense, and it is waterproof. But I agree, regular cement board is not waterproof by itself.

 

[Philip.I]

Thanks all for your replies. I found too many potential issues/unknowns and decided to rip the whole dang thing out. Thanks!