Choosing lumber for a home DIY project can be confusing. There are different grades, but wood that’s 2 inches or more in thickness is typically only graded for strength, indicated by #1, # 2 or #3. It tells the uninitiated purchaser nothing about its other qualities or defects.

Definition of a Defect

A defect can give a piece of lumber unique characteristics. In the lumber industry, a defect is something that will affect the integrity of anything constructed with it. Most defects are a result of the cutting, stacking or drying process and include:

  • Splits
  • Twists
  • Cracks
  • Bowing or curling
  • Cupping
  • Crooking
  • Wane
  • Shake
  • Knots

The Department of Commerce and the American Lumber Standards Committee are responsible for setting grade standards for lumber.

Knots and Appearance

Lumber with a #1 designation is stronger because it has fewer knots and the knots are smaller. It’s also deemed more attractive by buyers.

Conversely, lumber with a #2 rating is seen as less attractive due to larger knots and a greater number of them. Lumber in this group is generally used for projects where the appearance isn’t a primary concern.

Grade #3 lumber is allowed a greater number of defects, as long as the defect doesn’t extend completely through the wood.

Prime Grade

This is created from some of the most attractive timber. It contains a minimal number of knots and has uniform color.


The highest grade of timber available, it has the least amount of knotting and defects, while exhibiting the highest level of strength.

Construction and Stud Grade

This is used for light framing, with any knots tight, encased and sound. Stud grade lumber is appropriate for vertical members of a structure.

Standard Grade

Also used for light framing, the number of knots isn’t restricted.

Utility Grade

The lowest grade of lumber, there are few restrictions on the number of defects it may contain.

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