I'm trying to take up the residual "thinset" mortar left under some 16" tiles over concrete...

Question

What's the best way to get the thinset, mortar, grout lines up so the floor is smooth enough to lay new flooring ( hardwood)?

Answer 1

There's a tool used to scrape concrete flooring clean of grout etc...it's a long-handled tool with a flat, thick hoe on the other end. It has a bit of weight to it and you just scrape it over the rough spots...gravity will usually clean it well enough.
If you're going to put down hardwood flooring, your vapor barrier and other furring strips, etc, should also negate the need for a silky-smooth concrete floor.
The scraper will remove 100% usually though, just depends on how much scraping one is willing to do....it goes pretty quickly..
good luck

Answer 2

If you mean you've removed the tiles and what you have left is thinset with float marks, thinset is pretty hard to remove but there are some things you can do. Coffee or vinegar will help soften it but then you'll need to scrape it all up which is a big job and a huge mess. You might just apply more thinset to level the area. It also won't hurt to simply apply thinset and tile right over it. The marks left will give it some tooth which can't hurt. You can spread the new thinset in the opposite direction from the marks and make sure there is good contact when you apply the tiles.

Answer 3

Home Depot rents a 7"angle grinder/vacuum system that is excellent for this. You will have to buy the grinding wheel but this system will leave you with a nice, smooth floor, which you will need to lay a wood floor. Any other method will be time consuming and back-breaking.

Answer 4

Use a scraper would be the cheapest. If you don't mind the xtra cost, the best way would be to put down 1/16 plywood for a new subfloor.