My husband and I have a huge issue right now. Some guy messed up our tile job completely, so we are removing it all and replacing it ourselves (should have done it ourselves in the first place). The tiles all popped up in whole pieces- the “contractor” did not back butter the tiles. Instead, he put all the thinset on the backer board that we just recently put down ourselves with screws (and taped and mortared the seams). Now all of the thinset is stuck to the backer board. We need to use this backer board again. How the heck do we take this stuff off? It’s really thick !! We’re talking about 320 sq ft.... Would it be okay if we sanded some of it down and then poured a self leveler over it? Please say yes.... Thank you!
For a small area, a grinder with a silicon carbide wheel will clean thinset off, but it is real messy. For your 320 sq ft area, it could be done, but I would be inclined to pull the backerboard up.
Was the backerboard thinset to underlayment plywood or something like that?
If height is not an issue, you might consider thinsetting new backerboard to the existing, after using a grinder to level out the high spots.
Sorry I cannot offer a more definitive solution; you are in a hard spot.
I would use a scraper like this (blade nearly perpendicular to floor). Pull rather than push.
Be sure not to repeat the mistake. Level and/or use larger notches.
I had this same issue when I replaced my kitchen ceramic tile with hardwood 20 yrs ago. I tried several products before finally finding one that works from Home Depot. I am truly sorry I can't recall the name/brand--but it did work well in dissolving the thinset. I took a grinder to the edges of a square-point shovel to make it sharp. Applied the product. Waited 20-30min. Then scraped up the thinset/mess with the shovel and a lot of elbow grease. The point is-- there is a product that will work. It may take a few tries to find it, but something out there does work. Grinding sounds like a LOT of work, a LOT of dust, and less than ideal (FLAT) results.
As to the back-buttering tiles question, I'll take isherwoods' word for it, but I have never seen a Pro that did not back butter tiles. It could be a regional thing?