Lumber Grades

We’ve been northern Michigan’s lumber experts since 1904. So we can help you choose the right wood for your specific project. We’ll help you understand wood basics and specific grade information for softwood, hardwood, plywood, and treated lumber. So you can build with confidence and get the job done right.

Softwood Grades

Hardwood Grades

Plywood Grade & Exposure

Treated & Cedar

Lumber 101: Basics

Softwood Grades

Softwood lumber is categorized into framing/dimensional lumber or appearance boards. Other grades exist for utility and industrial applications (such as mining) that are not applicable to contractors and consumers. Broken into Common Yard Lumber and Select Yard Lumber, the most common grades (from highest to lowest) for retail applications are C Select, D Select, 1 Common, 2 Common, and 3 Common. All of Northern Building Supply’s softwood lumber is KDHT.

C Select

(Choice*) Highest grade softwood for cabinetry and interior trim, almost completely free of defects.

D Select

(Quality*) Similar to C, this has a fine appearance with dime-sized knots or less. *Idaho White Pine label

1 Common

(Colonial*) High-quality pine with a knotty look. Knots are tight and small. Fine appearance.

2 Common

(Sterling*) Slightly larger, but tight knots. General woodworking projects and paneling/shelving.

3 Common

(Standard*) Still used for paneling/shelving, also found in crates, fences, siding, sheathing and some industrial use.

Framing & Dimensional

The most common grade for framing and dimensional lumber is #2 SPF (Spruce Pine Fir). Within that grade, there’s a fairly large allowance for knots and bark. We buy premium SPF from our mills. It’s not a recognized grade, but an additional visual inspection. Experience has taught us which mills deliver true premium lumber. Trusses and support lumber are stocked in fir – because it’s better structurally

In-Stock Now

  • 2×4 and 2×6: #2 or better premium SPF
  • Fir Trusses: #2 or better “select structural”
  • Fir Support lumber 2×8, 2×10, 2×12

The Cut Matters

We discuss nominal vs. actual sizes in Lumber Basics. But let’s talk length. Because the big box store lumber can vary we purchase Precision End Trim lumber. Save time and frustration laying out your project by having lumber you don’t have to cut to a standard length.

Precision-End Trimmed (PET)

This lumber is both trimmed square, and to a tighter manufacturing tolerance (+/- 1/16″ in no more than 20% of the pieces) for length.

PET Sizes You’ll Find

Save frustration in your 2×4 and 2×6 lumber in the following sizes:

  • 92-5/8” (ideal for framing interior walls with the top plate, etc.)
  • 96″ (yes, it’s really 8-foot)
  • 104-5/8″ (ideal for framing 9-foot ceiling interior walls)

Hardwood Grades

In the case of hardwood lumber, the primary grading concern is appearance. Grading is completed based on the size of clear surface and percentage unblemished.

FAS (First And Second)

At least 6 inches wide, 8 feet long, and 83.3% clear on the poorest quality side.

Select

A board that’s at least 4 inches wide, 6 feet long, and is 83% clear of blemishes

#1 Common

A board that’s at least 3 inches wide, 4 feet long, and is 66% clear of blemishes.

#2 Common

A board that’s at least 3 inches wide, 4 feet long, and is 50% clear of blemishes.

FAS (First And Second) Grading Example

Click images for a larger view. Hardwood grading varies based on the characteristics of certain species and their grain characteristics. For a full illustrated grading guide, consult the NHLA illustrated grading guide.

Plywood Grades

Several plywood grading systems exist. Generally speaking, they follow an A, B, C, D grading with A being the highest grade. Plywood is also rated based on exposure to the elements on a scale of Exterior, Exposure 1, Exposure 2, and Interior.

Exterior

Fully waterproof bond (glue) between the layers and designed for applications subject to permanent exposure to weather and moisture.

Exposure 1

Fully waterproof bond but not for permanent exposure to weather or moisture.

Exposure 2

Interior type with an intermediate bond. Intended for protected construction applications where slight moisture exposure can be expected.

Interior

Interior applications only.

Additional Plywood Grade Information

If you find two grades listed such as A-C the face side is the higher grade (A) and the back side is the lower grade (C). You will also find plywood rated as Sheathing, Stud I-Floor, or siding.

The Engineered Wood Association has APA trademark stamps for each. Most consumer purchases are typically sheathing classification.

A

Smooth, paintable surface. Repairs to the veneer like replacing knots with patches can be made, but no more than 18. Used for projects like cabinets.

B

Solid surface. Minor splitting permitted.

C

Tight knots and knotholes allowed. Can also have discoloration and sanding defects on the surface as long as it doesn’t impair strength.

D

Larger knots and knotholes permitted..

Treated Lumber

The American Wood Protection Association publishes standards addressing both Above Ground and Ground contact treated lumber. This graphic gives a good general idea about which wood you should select for your project and how to read the end tag. As always, feel free to ask the experts at Northern Building Supply.

Treated Lumber We Stock

Pressure treating lumber results in resistance to rot, decay, and termites. It is most successful in pine species. Specifically, the most common varieties of treated pine are Red, Ponderosa Pine, and Southern Yellow Pine.

For exterior structural needs, we carry and recommend #1, Southern Yellow Pine – it is stronger than Red or Ponderosa Pine.

Northern Building Supply stocks ground-contact treated lumber only because it is the best protection.

Decking & Frame

Our treated dimensional lumber is the highest-grade #1 Southern Yellow Pine ground contact lumber. We also stock 2×4 and 2×6 Appearance-Grade Ponderosa Pine for a smoother grain.

We carry premium Southern Yellow Pine deck planks as well as Ponderosa Pine in Patio #1 (the highest grade)

Cedar Lumber

Cedarwood is in a class by itself. Selected for many reasons, it provides some of the same resistances as pressure-treated lumber. It is primarily suited as an exterior, non-framing softwood, popular for siding, decking, trim and shake shingles.

We do NOT generally recommend cedar lumber for structural purposes.

Learn more about cedar grades from the Western Red Cedar Lumber Association (WRCLA)

Cedar We Stock

Below is a list of our regularly-stocked cedar lumber. You can find these cedar boards in Western Red Cedar, plus we also have rough saw random length / random with White Cedar.

 

Nomenclature associated with cedar lumber:

  • KD = kiln dried
  • S4S= smooth 4 sides
  • STK = sound tight knot
Western Red Cedar Siding – Raw

A grade bevel

  • ½ x 6” 8”
  • ¾ x 8” 10”

STK bevel 5/8 x 6” 8”

Rough sawn channel lap 1x 6” 8” 10”

Primed Cedar Siding

Clear finger joint primed- bevel ½ x 6” 8”

Cedar Boards – Raw

#3 & Better Rough Sawn

  • 1×4” 6” 8” 12”
  • 5/4×4” 6” 8” 12”
  • 2×4” 6” 8” 12”

A & better KD S4S

  • 1×4” 6” 8” 12”
  • 5/4×4” 6” 8” 12”
  • 2×4” 6” 8” 12”
  • 4×4”

D & better rough sawn

  • 1×4” 6” 8” 12”
  • 5/4×4” 6” 8” 12”
  • 2×4” 6” 8” 12”

#2 knotty S4S

  • 2×4” 6”
  • 4×4”

 

Cedar Pattern Boards – Raw

A & better profile WP4 1×4” 6”

D & better profile WP4 1X6”

#3 & better rough sawn 1×4” 6” 8”

#3 & better rough sawn center match 1×6”

Primed Finger Joint Cedar

A & Better

  • 1×4” 6” 8” 12”
  • 5/4×4” 6” 8” 12”

Rough Sawn

  • 1×4” 6” 8” 12”
  • 2×6” 8” 10” 12

Lumber Basics

Hardwoods

Hardwoods are the deciduous trees that (lose their leaves in the fall/cold months.) There are more than 200 varieties that prove both pliable and plentiful for woodworking. The most common ones are oak, maple, walnut, hickory, and mahogany. Hardwoods are classified by pore openings either Closed Grain (smaller pores) or Ring Porous (larger pores). Closed grain examples include maple and cherry. Ring Porous examples are species such as oak, poplar, and ash. Hardwood trees take longer to mature, so their density tends to be more expensive than softwood species. Hardwood is thus best suited for fine woodworking like cabinetry, furniture, and flooring.

Softwoods

Softwoods are coniferous (evergreen trees) like cedar, pine, fir, and spruce. Only about 25% of softwoods are used in woodworking. As a Closed Grain (smaller pores) product, softwoods don’t tend to have a very defined grain in the finished product. As a softer wood, they can be dented – using even your fingernail. Softwood absorbs moisture much easier, requiring treating for use exposed to the elements. Faster-growing than hardwood counterparts, these straight-grained species are less expensive and well suited for house framing, construction, and outdoor projects (when treated) like decks.

Moisture Content

The moisture content of wood is measured at the time of manufacturing. As a piece of lumber dries it shrinks. This shrinkage can lead to defects

  • S-GRN. Surfaced in green condition.
  • S-Dry. (Surfaced dry.) Moisture content measured less than 19% after manufacture.
  • MC15/KD15. Moisture was 15% or less at the time of manufacture.
  • KDHT. (Kiln-Dried and Heat-Treated.) Dried to < 19% moisture content with core brought to 56 degrees C for 30 minutes.

Because heat-treating lumber kills insects and fungi, lumber that is shipped globally must be heat treated.

Nominal vs. Actual (Sizes)

Structural/dimensional softwood lumber is referred to by its common nomenclature (such as 2×4). This size isn’t the exact dimensions of the board, this is the “nominal size”. Click the photos to see a larger version of the charts. Similarly, hardwoods have a standard thickness as it is cut into quarter-inch increments.

Lumber Defects

Northern Building Supply screens every shipment of lumber. We only buy kiln dried and heat-treated lumber because less moisture leads to less warping (as pictured). Warping often occurs when sides dry unevenly. We also use only the best mills and wholesalers for our lumber. We’d rather send a shipment back than delivering anything but quality lumber to our customers. When you’re ordering a large order for delivery, you don’t get to hand-select each board so our quality standards really pay off. The total procurement cost of getting quality lumber the first time decreases the time and money you spend.

Specific Defects

Both hardwood and softwood can present defects. Sometimes it’s the tree, or how the lumber was milled. Not every defect is a problem depending on your application. If you need help selecting the right grade for your project, talk with our knowledgable staff.

Bow

Cup

Split

Check

Knot

Twist

Crook

Shake

Wane

Western Wood Products Association stamps

The Western Wood Products Association (WWPA) is the largest association of lumber manufacturers in the United States, spanning a dozen western states. It’s certification stamp contains: a. A WWPA Certification Mark b. Mill Identification c. Grade Designation d. Species Identification e. The Condition of Seasoning (moisture)

A full guide to interpreting WWPA stamps is available free from their website. Users must be registered, but free registration does not require you to be an industry insider.

Need to talk to an expert about your next project?