First time tiler about 1/3 the way through my living room w/ 13 x 20 porcelain Dal-tile on top of Hardibacker. I just realized that I was using the pre-mix thinset I bought for the Hardibacker to subfloor bond for the porcelain. How big of a problem do I have? What kind shoud I switch to? Thanks!
Why did you use mastic to install the Hardie in the first place? That stuff is much more expensive and not as good.
It's definitely no good to set the tiles. Once you're ready to start over, get a decent quality modified thin set mortar. A "basic" grade starts at about $13 per bag. The better ones in the twenty plus range. The are many brands and they should all be good. Some are just better than others. We don't know what brands are available near you.
TILE GUY - retired- TROY, MI - Method & Product suitability consulting.