Hardwood Floors December 2025/January 2026

By Bob Goldstein

Flat. A simple four-letter word with so many connotations. If you are water skiing, a flat lake or body of water makes it easier and safer. Flat roads are easier to pedal a bike on. On the other hand, flat beer, flat line, and flat tire all have negative connotations. In our trade, we need a flat subfloor; the flatter the better.

One strives to meet the industry standard of flat to within 3/16” in a 10’ radius, or 1/8” in a 6’ radius. When nailing a wood floor, the subfloor should be flat to ¼” in 10’, or 3/16” in 6’. The science or geometry behind the numbers is simple – the shortest distance between two points is a straight line. Let’s say we are measuring a line 5’ long on an acceptable flat surface, and the distance from point A to point B is 5’. Now, let’s say the surface between point A and point B has a hump in it. That means the distance is longer from points A and B, because the hump (or valley) adds to the distance. So, one run is on a flatter surface than the next run; this is when the installation becomes a nightmare. While we’re discussing flatness, let’s examine the term level. Level and flat are not the same. They are not interchangeable. You can have a wheelchair ramp where the floor on the ramp is flat, but obviously, the ramp is not level. I like to demonstrate this fact by using a coffee table. The tabletop is dead flat. When I lift one end of the table, it is no longer level, but it is still flat.

The bottom line is that if you want to elevate your business and offer ornamental floors, first pay close attention to the subfloor flatness, and then choose a manufacturer you trust to provide quality products.

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