We're repairing an existing floor that will receive floor tile. All high spots that don't meet a 1/4-inch-in-10-foot tolerance have to be removed. Is there a quick, low-cost way to do this?
Lowell Brakey, a Kansas concrete contractor, has developed a slick way of doing this. His crew puts water on the floor to find the high spots. Then they grind the spots down using a walk-behind heavy-duty grinder that looks like a floor buffer but with diamond blades on the bottom. Brakey says it's important to know immediately when to stop grinding because the blades cut so rapidly. To quickly alert the operator that it's time to stop, he mounted a laser receiver on the grinder. The crew first puts the grinder on a section of floor that's at the right elevation and adjusts the transmitter elevation until they get an on-grade indication from the receiver. Then they move to each high spot and grind until the on-grade indicator signals them to move on. You also could grind down high spots with a terrazzo machine with Carborundum stones. But Brakey says the diamond grinders are much faster.