Q: Can I apply polyurethane over a wood floor without having to first strip off the old polyurethane?
A: Yes, a polyurethane-finished hardwood can be recoated if you take the proper steps to prep the finish. First, lightly sand with No. 2 steel wool or a dull 120- to 150-grit abrasive screen using a heavy floor buffer. Using a sanding block or 1/4-sheet sander, sand the corners, edges and beneath cabinet toe-kicks. Sweep up the dust and vacuum to clean the entire floor. Wipe a tack cloth over the floor to pick up remaining dust or debris. (Dampen the cloth with water, floor cleaner or paint thinner). Reapply the oil-based poly along the edges of the floor with a brush and then recoat the remainder of the floor with a lamb’s wool applicator (or synthetic paint pad for thinner coat). Always apply the finish in the same direction of the wood grain.
Note: If using a water-based topcoat, avoid sanding the floor with steel wool and don’t use paint thinner on your tack cloth. You will also need a special applicator for water-based polyurethane.