Lumber is graded based on how it will be used. The fewer knots and defects, the higher the grade and the more expensive it is. Since the price can often double from one grade to the next, it’s important not to buy a better grade of lumber than needed.
Lumber from cone bearing trees—like pine, redwood, and fir—are grouped together as softwoods and graded based on either their strength or appearance. Knots and other defects result in a lower grade. Most two inch thick softwood lumber is graded for its strength rather than appearance.
The common grades found at your local lumberyard from best to worst are:
- #1: Construction grade.
- #2: Standard grade.
- #3: Utility grade.
- #4: Economy grade.
Softwood lumber that is graded for appearance is used mainly for facing boards and other finish work. The highest quality appearance lumber is known as “finish” followed by “select.”
Each category is graded from best to worst as:
- A: Clear with no knots.
- B: Contains a few minor defects. Often combined with A and sold as B & Better.
- C: Some small tight knots.
- D: A few knots and defects.
Some specialty softwoods—such as redwood and western cedar—are graded on the amount of rot resistant heartwood as well as defects.
The more common grades of redwood are:
- Clear all heart: No defects and all heartwood on the graded side.
- Heart B: Heartwood with a few knots allowed.
- Construction Heart: Heartwood with larger knots allowed.
- Deck Heart: Similar to construction heart, but graded for strength.
- Clear: No defects but some sapwood.
- Construction common: Knots and sapwood allowed.
Softwood lumber contains a stamp indicating the name or number of the mill where the lumber was processed, the species of wood, how it was dried, the grade it received, and the organization that certified the grading.
Some of the common species abbreviations found on softwoods are:
- D FIR: Douglas fir.
- DOUG FIR-L: Douglas fir or larch.
- HEM-FIR: Hemlock or fir.
- IWP: Idaho white pine.
- PP: Ponderosa pine.
- PP-LP: Ponderosa pine or lodgepole pine.
- S-P-F: Spruce, pine, or fir.
- SYP: Southern yellow pine.
- WEST CDR: Western cedar.
Hardwoods—such as oak, cherry, walnut, and poplar—are graded based on the amount of clear material that can be obtained from the board. Since they are often sold rough, hardwoods are usually not stamped.
The grades from best to worst include:
- FAS: “Firsts and Seconds” must be 6” or wider and 8’ or longer with 83% of the board clear of knots and defects.
- Select: Similar to FAS but allows boards as narrow as 4” x 6’.
- #1 Common: Minimum of 3” x 4’ and larger with 67% of wood clear from knots.
- #2 Common: Same as #1 but with only 50% clear of knots.