I am remodeling a small bath in a high rise. I have removed the small 1"x1" old tile but the 1 inch thick plus mortar still remains. It was poured over a 5" think concrete slab floor of the high rise. How do I get this mortar off? Can I install marble over this mortar without removing it? Thanks

I am guessing a lot of this mortar is for leveling... I guess the troweled material if you can't chisel it off easily will have to be ground off with a rented floor grinder. It is messy so wear protective clothing and air prep gear. Wish I had a magic wand for you, as I've been there and done the later... It's not pretty till your all done!

I do wonder why the mortar is 1" thick, maybe desgrunner is correct about leveling but normal mortar is 1/4" thinset. You can rent a rotary hammer and jack hammer the mortar out. I would not put new tile on the old mortar unless it was 100% in tip top condition and your new floor will be 1/4" higher than the old, got room? If it is tip top and the 1/4" doesn't screw up your doors or fixtures you can do it. You can raise the toilet flange with a flange spaver, $2.99 at Home Depot.

Depending on the age of the floor installations. In many high rise buildings, it is common to see a mud base as underlayment for flooring. If the 1" thick mud base is intact, I would install on top of it by skimming the surface with thinset and using an isolation barrier mostly to keep the gray or brown color from the mud and previous thinset from staining the marble. Then install the marble on top.

Good luck,
Willy
Marble and Granite, Tile and Grout, Leaky Shower