The Pro's Guide

How To Specify Hardwood Flooring

Chapter 2

Lumber Grade

Chapter 2: Lumber Grade

The National Wood Flooring Association (NWFA) uses a standard lumber grading system that assesses how much variation in natural color and character the unfinished flooring has.

In chapter 2, we’ll learn more about how the grading system works and compare the four lumber grades.

What is Lumber Grading?

Appearance-Based System

This grading system is only based on the appearance of the wood, and is not an indicator of quality. Strong and durable flooring is made from lumber with any of these grades, and the system has strict requirements on what types of imperfections are permissible.

To make the grade, any knots, streaks and holes cannot compromise the strength and soundness of the flooring product.

What is Lumber Grading?

Compare the Four Different Grades

#2 Common

Sound natural variations and manufacturing imperfections create a floor with a lot of character and visual contrast.

#1 Common

Floors feature noticeable variations in color and a variety of natural wood characteristics.


Variations are less prominent and are primarily a result of the natural color differences in the inner (heartwood) and outer (sapwood) parts of the log.


This grade provides the most uniform overall look in a finished floor, with minimal character marks and discoloration. Products with a Clear grade are usually premium-priced.

Credit: National Wood Flooring Association (NWFA)