Why do we sand a wood floor? If this question were asked of flooring contractors, typical responses might include: to repair damage to the floor; to change the color; to change the finish sheen; or to protect the investment (preserving and restoring the beauty of a wood floor found under the carpet that was removed, for example). Yes, there are even more reasons, however, the main reason to sand a floor, whether new or existing, is to give beauty to a renewable resource that can usually be repaired instead of replaced. A typical nail-down, ¾-inch, tongue-and-groove wood floor can be resanded several times by a good professional flooring contractor; most beginning floor contractors would have a tendency to sand too much off the floor, decreasing the overall life and leaving little or no wood for the next sanding. Taken from that perspective, contractors sanding a wood floor have a huge responsibility to protect their customer’s investment and make that floor last as long as possible.
To that end, I’m going to answer some of the most common questions asked by beginner floor sanders. The answers are aimed at contractors new to sanding, however, if you have been sanding floors for a while, you might want to continue reading, for an old dog can still learn new tricks. For the purposes of covering the basics, here we’re assuming you’re using the three standard sanding machines: the big machine, the edger and the buffer.
That said, here are 10 common questions about sanding basics:
1) Why can’t I skip more than one grit in the sanding sequence?
Your goal in a sanding sequence is to use progressively finer abrasives to flatten the floor and smooth out the wood to get it ready to accept new finish—all while taking off as little wear layer as possible. If you skip more than one grit in the sanding sequence, you end up with the first cut leaving deep scratches into the wood, and the second cut having too fine of a grit to take out the first scratch. This peak-and-valley profile will leave a rough-looking floor and, if stained, cause uneven staining (see the “Guide to Abrasives” sidebar on page 58). Another result of skipping grits is early finish wear in heavy traffic areas. The reason is that the peaks will not have as much finish on them as the valleys, so the finish on the peaks will wear off faster.