Selecting Western Red Cedar Grades
Most outdoor cedar sold in Canada is western red cedar (Thuja plicata). Two boards from the same species can behave very differently outdoors depending on grade and on how much of each board is heartwood. Picking the right grade is usually a larger factor in service life than the brand of finish applied later.
Heartwood versus sapwood
The natural durability cedar is known for comes from extractives concentrated in the heartwood, the darker inner wood of the tree. Sapwood, the paler band near the bark, contains little of these extractives and is not rated as durable. When a board shows a wide stripe of light sapwood along one edge, that edge is the part most likely to weather and decay first.
For ground-contact or moisture-prone parts, such as the bottom rail of a fence or the lowest board of a raised bed, boards that are predominantly heartwood are the more conservative choice.
The common appearance grades
Cedar is graded mainly on appearance rather than strength, because it is rarely used as primary structural framing. The grade names below follow the appearance categories used by the Western Red Cedar Lumber Association and Canadian mills.
| Grade | Knots | Typical use |
|---|---|---|
| Clear (e.g. Clear Vertical Grain) | Essentially knot-free | Trim, fascia, exposed cladding, fine joinery |
| Select Knotty | Small, tight, sound knots | Quality fences, pergolas, visible structures |
| Knotty / Standard | Larger and more frequent knots | Utility fencing, posts, rough framing |
Higher appearance grades cost more because clear cedar comes from larger, older logs and yields less per tree. For a back fence, a knotty grade is often a reasonable balance; for trim that sits at eye level, the smoother select or clear grades earn their price.
Grain orientation
Boards are also described by grain. Vertical-grain (quarter-sawn) boards show tight parallel lines on the face and tend to stay flatter and cup less than flat-grain (plain-sawn) boards, which show the wider cathedral pattern. Where movement matters, such as wide deck or cladding boards, vertical grain is the steadier option.
Matching grade to the job
- Privacy fence boards: select knotty is a common, cost-aware choice; keep heavier sapwood boards for upper, drier positions.
- Posts and rails: structure and durability matter more than looks, so prioritise heartwood content.
- Raised garden beds: untreated cedar is preferred for food growing; knotty grade is usually adequate since appearance is secondary.
- Visible trim and cladding: clear or vertical-grain grades for a clean, stable face.
Storing cedar before you build
Cedar delivered to a site is rarely at its final moisture content. Stack it flat on level supports, keep it off the ground, and let air move around it under cover. Building with boards that are still adjusting to local humidity is a common cause of gaps and cupping that appear weeks after a project looks finished.
References
· Western Red Cedar Lumber Association — grades and product information: realcedar.com
· Canadian Wood Council — wood species and durability: cwc.ca
· Natural Resources Canada — Canadian forests and wood products: natural-resources.canada.ca