Old thinset mortar should be removed from a floor before installing new tile. When you remove old floor tile, you will sometimes get small pieces of the thinset mortar to pull up along with the tile. Most times, however, once the tile is up, you are left with small mounds of thinset all over your subfloor. These mounds need to be scraped, chipped and smoothed down to prepare the subfloor for new flooring.
Things You'll Need
4-inch hand scraper
Electric chipping hammer
4-inch grinder with concrete blade
Bucket of water
Hold the 4-inch scraper with both hands at a sharp angle to the floor.
Push the scraper blade across the cement toward a mound of thinset. Do not stab at the pile with scraper as this will break the blade quickly. Instead, try to push the blade like you are going to push all the way through the mound. Some sections of thinset will come up in large, single pieces, while others will need further work.
Sweep up any loose pieces of thinset and place the garbage in buckets for easy removal. The cleaner you keep the floor while working on it, the easier it will be to see the areas that need the most work.
Plug in the chipping hammer.
Hold the blade of the chipping hammer at a sharp angle directly on the base of a mound of thinset.
Squeeze the hammer's trigger and press into the mound to begin chipping away at it. The vibration of the chipping hammer will loosen hard-to-remove chunks of thinset, while some pieces will still require more attention.
Plug in the 4-inch grinder.
Wet any remaining trouble areas with a sponge and water. The water will keep the grinding from making too much dust.
Turn on the grinder and hold it with both hands so the blade is facing the ground.
Place the face of blade directly on top of the mound of thinset.
Move the grinder in left and right sweeping motions as if you're using a hand sander.
Smooth the remaining mounds of thinset until the floor is smooth again.
Sweep up any remaining waste and dispose in buckets for easy removal.
Always wear protective eye wear when chipping and grinding concrete.