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Grading - Western Red Cedar Cedardeck 40x140mm

Species: Western Red Cedar
Grade: Architect Knotty
Grading Body: Western Red Cedar Lumber Association (WRCLA)
Product Page: Western Red Cedar Cedardeck 40x140mm

The purpose of this document is to provide a detailed, factual and accurate description of the material along with the officially published grade description where applicable.

It goes without saying that reading this description is no substitute for seeing the actual material. We are always happy to send out hand samples, but they have very limited use in determining the overall quality - it is impossible to cram every feature and characteristic that you might encounter in a delivery of timber on a single 6” sample. For this reason we encourage you to visit our premises and take a closer at the product before you buy.

What is a timber grade?

The grading of timber can be defined as the sorting of wood sawn from a log into different qualities relating to classifications for appearance, end use or strength. The practice is essential to maintain consistency and to ensure reliability from order to order.

A timber grade is simply a minimum standard describing the extent and limitations of the characteristics permitted in a piece of timber depending on its end use.

Silva Architect Knotty Grade

Some less technical timber grades are more subjective and are usually related only to appearance. These are sometimes referred to as vernacular or colloquial grades. Architect Knotty is a grading standard specifically created for Western Red Cedar decking by the WRCLA. Although it’s not an official grade it sets a generally accepted standard that WRCLA member mills adhere to. It is important to be aware that the same timber grades can vary in quality and appearance between different manufacturing mills. The best policy is to personally examine the wood before you buy it unless you are familiar and trust a specific supplier.

This particular product is manufactured by one of the most respected primary producers of Western Red Cedar in North America. It is of a consistent quality that meets and exceeds the WRCLA Architect Knotty grading standards.

It is ideal for professional landscapers and deck installation companies looking for an attractive and high quality product with proven performance characteristics at a reasonable price point.

Pack Inspection

In the above video we inspected a pack of Western Red Cedar Cedardeck 40 x 140mm consisting of 128 boards at 3.66m length. We've documented our findings below in relation to the grading rules to give you an understanding of what to typically expect from a shipment.


Wane is strictly limited to one face and kept to within ¼ thickness and ¼ width of the board on the reverse face only . On the pack we examined we found 18 instances of wane.


Knots are generally sound and tight however two not firmly fixed (NFF or soft) knots are permitted per 3.66m. NFF knots of half the maximum size of sound knots are allowed. In the pack of 128 boards we examined there were a total of 18 NFF knots.

Maximum permitted knot size: 73mm

Silva Architect Knotty does have large sections of clear material with some boards only exhibiting one or two knots. Although this is clearly a knotty grade, we feel that because the knots are not overly numerous they do not detract from the overall appearance, but rather they enhance it by adding to its character.

When we examined the pack of 192 lengths of 3.66m 40 x 140mm Architect Knotty grade decking which is featured in our video we found that the average number of knots per board is only 10 and the average size of the knots was approximately 25mm.

Holes are not permitted.


Splits of approximately the width of the board are permitted within the grading rules. In the pack we examined we found 2 boards with minor end splits. You may encounter the odd small split on the edge or end, which can either be trimmed out or glued.


Silva Architect Knotty is a mixed grain product. This means that it contains boards with grain running perpendicular to the face (vertical grain) and boards with grain running parallel to the face (flat grain).

Damaged boards

In this pack we found 3 damaged boards that our pickers would typically remove before sending out and 6 more with minor damage that would either not be visible when installed or easily trimmed off the ends.


Skip is an area on a planed board where the planer has failed to remove all of the rough surface during the manufacturing process. Small patches of skip are permitted within the grading rules which can easily be removed by sanding the affected area.

Raised Grain

Raised Grain is a roughened condition of the surface of a planed board in which the hard summerwood is raised above the softer springwood, but not torn loose from it. As with skip occasional patches may be encountered however they are easily removed by sanding.

Colour Variation

As with any natural wood product you should expect colour variation both between boards and within individual boards.

This particular pack was randomly selected and we know it to be representative of Silva Architect Knotty grade Western Red Cedar decking. The quality of raw material that we receive from our supplier is consistent from one shipment to the next, so we are confident that the material you receive will be of a quality similar to the material described above and shown in the video. That said, please bear in mind that the next pack we could have chosen may have had more imperfections or it may have had fewer imperfections.

You are likely to generate a small amount of wastage when using this product, but by planning your cuts prior to installing this will be minimal.


Silva Architect Knotty grade Western Red Cedar decking is a high quality product that displays minimal minor imperfections but in general it far exceeds industry standard and is suitable for all types of residential and commercial decks.

Percentage of boards usable on both faces

This product is graded as decking therefore boards may exhibit material or manufacturing defects on the reverse of the board. We found that approximately 75-80% of the boards in this pack have two good faces, the remaining having one usable face.

Visit the product page: Western Red Cedar Cedardeck 40x140mm

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