There are different types and strengths of lumber suited for every kind of job. Lumber grading helps builders and consumers get the right product for each project.

Why We Grade

If you’re framing a house, the lumber you use has to be strong enough to support the structure.

If you’re building a birdhouse for your backyard, on the other hand, you don’t need the same load bearing capacity. Lumber grading is how our industry tells consumers whether the board they buy will meet their needs.

This is important because it helps consumers put more of what we harvest to good use. If we sold nothing but heavy-duty construction-grade lumber, tons of good materials for lighter uses would go to waste.


Lumber grading is a role that’s been part of our association from the beginning, and today, we’re still the primary certification agency in Alberta.

We’re responsible for ensuring the quality of every piece of stamped lumber that comes from our member companies, and for verifying that the grades assigned by members’ mills are accurate.

We’re proud of how accurately our members grade their products. Only 0.11% of the 3.5 billion feet of lumber they graded last year needed to be re-graded. AFPA also trains and certifies the lumber graders who work for individual companies, with training programs held in the spring and fall.

Beyond lumber grading, AFPA is a certification agency for the Canadian Heat Treated Wood Products Certification Program under the Canadian Food Inspection Agency.  We work in that capacity with guidance from the Canadian Lumber Standards Accreditation Board. We also monitor wood packaging materials, pallets and containers for their ISPM15 (International Standards for Phytosanitary Measures) certification.

Understanding Lumber Grades

Every piece of lumber sold is stamped with details about its lumber grade.

That stamp provides information about characteristics of the wood – like moisture content, tree species, treatments performed on the lumber and any imperfections. These are all characteristics that can affect the lumber’s quality, strength and appearance.

Building codes specify what grades of lumber can be used in which ways during construction. Building inspectors will look at the grade stamps to make sure that the materials used can safely bear the load they’re carrying, and engineers look at lumber grade stamps to inform how the wood will be used in the structure and design of buildings.



Registered Symbol of the Certified Agency

AFPA – Alberta Forest Products Association

Agency Logo.

• Most provinces have a certified agency that manages lumber grading under the National Lumber Grading Authority


Species or Species Group

SPF – Spruce, Pine, Fir

Species group that represents the wood species included.

• SPF (spruce, pine, and fir) are the most common species group in Canada


Moisture Content

KD – Kiln Dry – 19% or Less

Identifies the moisture content and drying process of the wood.

• Most lumber in Alberta is kiln dried to a moisture content of 19% or less, which is considered dry lumber. An advantage of using dry lumber is that most of the shrinkage has been achieved prior to purchase; wood does most of its shrinking as it drops from 28-19%. Dry lumber will have already shown its drying defects and will also lead to less surprises in a finished building, as the product will stay very close to the dimension it was upon installation. Dry lumber will be stamped with the letters S-DRY (for surfaced dry) or KD (for kiln dry)

• Lumber left to dry in the open air over a long period of time to reduce the moisture content to 19% or less is given an S-DRY classification once surfaced

• Surfaced lumber over 19% moisture content is given an S-Green classification


Heat Treatment

HT – Heat Treated

HT indicates the wood is heat treated.

• The lumber is treated to ensure the core temperature of the wood reaches 56°C for at least 30 Minutes. This kills bugs and enables phytosanitary safe shipment anywhere in the world


Mill and/or Grader Identity

10 – AFPA’s Mill Number

Mill Number – where it was manufactured and graded.

• Each facility in Alberta has a number assigned to them


Grade Rule

NLGA – National Lumber Grading Authority

The National Lumber Grading Authority sets the rules and provisions for lumber grading in Canada.



STUD – Specifically used for studs

This is the grade given to every piece of lumber at the manufacturing facility.

• Structural grades include: Select Structural, 1, 2, 3, Stud

– Each graded piece of lumber can have different uses depending on the strength required for wooden structures being built

• Machine Stress Rated grade (MSR) – Lumber can also be grade stamped with a machine-tested strength (2.0E 2400Fb MSR, 1.8E 2000Fb MSR, 1.5E 1650Fb MSR, etc). This standardized rating is measured using a non-destructive, stress testing machine

• These grades are used by engineers to identify the strength of lumber required in design and construction of wood structures

Grading identifies the characteristics of each piece of lumber and considers flaws in the wood including:

• Knots
• Wane
• Shakes and splits • Decay and rot
• Moisture content • Warp

Grading usually happens at the manufacturing facility by sophisticated cameras and machine grading equipment as well as visual inspection by AFPA-trained graders.

Process and Technology

It used to be that every piece of lumber had to be fully, individually graded by hand.

Today, trained graders still do the final check, but advanced technology has made the process much faster and even more accurate.

Machine learning is starting to make its way into modern mills, and almost all mills now have laser scanning and automated grading machines. The machines rapidly scan and analyze huge quantities of lumber in fractions of a second, and apply the grade that is most appropriate based on the large data sets they’ve been programmed with. A trained lumber grader then confirms the grade assigned by the machine or re-grades the lumber if needed.

Some machines go beyond just providing a grade, suggesting how a piece of wood can be trimmed to optimize its usefulness. If there’s a long piece of lumber with a defect in one place, for example, we could cut it strategically to produce one shorter high-grade piece with no defect and one shorter piece that’s a lower grade, instead of one long piece of lower-grade lumber.

Of course, the machines are only as good as the people who design them, program them, run them, service them, and check their work. Lumber graders now use these technologies as tools, much like a doctor uses an MRI machine. The doctor still has to interpret the MRI – likewise, the machines we use in lumber grading aren’t a substitute for skilled and trained lumber graders. AFPA offers training courses in lumber grading twice a year to meet this need.


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