Q&A: What Are These Strange Raised Areas in this Wood Floor?

What are the raised areas? This is a sand and refinish; the raised areas are all the same, with some bridging across a board seam. The floor was sanded flat, water-popped and stained. There are three or four spots in this three-point section and none anywhere else. They are not in the finish coat—they are wood. — Brent Kelosky, Sport Floors Inc. (Koppel, Pa.)

Patrick Russell at All American Floor Sanding and Installation in Ocala, Fla., answers:

Those were existing dents that were in the floor prior to sanding. They were sanded flat, and when the floor was water-popped, the moisture made the compressed wood regain its normal shape, rising above the rest of the wood floor. This is similar to the technique of getting dents out of a wood floor with moisture and an iron—just that in this case, the waterborne finish provides the moisture, and the dents decompress without the added heat.

I first saw this on a maple job where the homeowner had huge dogs that had torn the floor up. We hadn’t done a real aggressive sanding—just a multi-disc enough to get the scratches out. After it was flat and we put down the seal coat, we saw these lines. After I crawled around on my hands and knees, I realized the lines were where the dogs had rounded the corner around the cabinet to go out the door—we hadn’t sanded deep enough to get out the compressed wood from the dents, and our waterborne sealer had made them rise.

Sometimes people suggest that boards with dents like this need to be replaced, but we find that water-popping helps a ton when you come across floors that have lots of dents. In our area, we have a lot of old dented pine floors, and we water-pop all the time when we come across a floor like that. We sand to 100, water-pop to raise the dented wood, then sand with 120—problems solved, with no need for board replacements.