Dark wood under an old rug?

Q. I’m sanding a floor from the 1910s where an old rug had been tacked down in the middle of the floor. There was no finish at all under the rug, but there was a coating of some kind around the edge, along the walls. The problem is that the area that was under the rug is much darker than the perimeter and no matter how much I sand, I can’t get it to lighten to match the edge. Why can’t I sand that wood clean?  Buddy W. New Jersey

A. We don’t see this often, but when we do, it’s unmistakable. Hardwood flooring that was never protected with finish oxidizes deeply and darkly over a long period of time. This appears most frequently in rooms where carpet was placed over raw wood, but the exposed edges of the wood floor were waxed or shellacked, and the result is a distinct and permanent line where the shellac ended.

We often see this in hallways where carpet runners were installed immediately after construction. Unfortunately, the only solution is to try to custom-stain the edges to better blend with the dark area, or simply to stain the entire floor dark. The discoloration is very deep and will not sand out.

To protect the floor under your rugs, and keep your rugs in place, check out the Rug Check Plus.