Catégories et spécifications du bois de construction


Categories Clear

Clear thuja has a limited number of natural characteristics and is specified when a higher quality appearance is desired. Clear categories of lumber are normally supplied green (not dried). When the customer requests it, air drying is done.

The gnarly categories

Thuja thuja has a more rustic appearance and is generally green (undried) in appearance and structure. When requested by the customer, air-drying is performed except for Lightweight Carpentry and Stringers and Wood Framing, which are available kiln-dried.

Surface textures

Saw Textured: The saw-cut surface obtained during the milling process, which uses circular or ribbon saws, is present on all four sides.

Planed Textured Surface: Timber acquires its texture through a milling process that uses rough planer blades. The rough texture is clearly visible on all four sides.

Four-sided planing (S4S): The smooth surface of all four faces has a uniformly sized product with a superior appearance. Sizes ranging from 2 x 4 inches (51 mm x 102 mm) up to 6 x 6 inches (152 mm x 152 mm) are generally available. Larger sizes are produced on special order.

No. 2 and Better Clear

This category should be specified when the best quality of raw timber is desired. Timber is healthy and well made. Its natural features do not detract from its natural beauty.

PLIB Classification Rule Paragraph – R 401 Export List

D and Better Clear

This category includes D Clear, C Clear and B Clear.

Category C and Better Clear offers beautiful, high quality and well made lumber. It is suitable for high quality landscape structures and exposed posts and beams for heavy wood construction. The members of the WRCLA produce this category without falls. In most cases, this category is sold with a specified grade D margin.

The D Clear category allows for more and larger natural features that are commonly accepted in the construction of outdoor structures. Some pieces of D Clear may require trimming to produce lengths that are useful for the intended use. Available planed or with rough texture.

Paragraph of classification rules
NLGA 203 b, c, d
WCLIB 150 b, c, d
WWPA 10.11, 10.12, 10.13

Knotty Appearance

It is a non-structural product manufactured to meet the appearance requirements of high quality projects. This material has very small dieback margins to give well-defined corners. It does not contain holes or other features. It offers good value for its end use with regard to appearance. Available rough sawn or planed to textured surface in nominal size of 2 inches (51 mm) and thicker.

NB: On request, Appearance Knotty beams are available with structural classification. Do not forget to specify that you want Appearance Knotty structural timber if you need a resistant wood.

Owner Classification Rule Paragraph

No. 2 and Better Structural

The material belonging to this category is evaluated according to its structural strength characteristics. The classification includes parts that are suitable for the Select Structural, N ° 1 Structural and N ° 2 Structural categories. Wood in this category is intended for engineering applications where strength is more important than appearance. Available planed or rough textured.

Paragraph classification rules
5 inches and thicker, with 2 inches more than the thickness
NLGA 130a, b, c
WCLIB 130a, b, cc
WWPA 70.10, 70.11, 70.12

The width is 2 inches less than the thickness
NLGA 131a, b, c
WCLIB 131a, b, cc
WWPA 80.10, 80.11,80.12

NB: Enter the category Light Framing

Enter in the category Joists and Slats of Carpentry

Beams, poles and standard planks

Planks in this category are intended for general construction, where functionality is more important than appearance. No structural value is attributed. Available planed or rough textured.

Classification Rule Paragraph
5 inches (127 mm) and thicker
NLGA 131 d
WCLIB 131 c
WWPA 81.11

NLGA – National Wood Classification Authority
WCLIB – West Coast Wood Inspection Office
WWPA – Western Wood Products Association
PLIB – Pacific Wood Inspection Office


Thickness and width
Nominal (inches)Rated (mm)Gross (inches)Gross (mm)Dressed (inches)Raised (mm)
51274-3 / 41214-1 / 2114
61525-3 / 41465-1 / 2140
82037-3 / 41977-1 / 2191
102549-3 / 42489-1 / 2241
1230511-3 / 429811-1 / 2292
More than 12More than 3051/4 of a gap6 mm apart1/2 of a gap13 mm apart

NB: The full sawn lumber has the same dimensions as the nominal sizes.

Classifications by category

Depending on the size, the western redcedar is classified as Light Framing, Joists and Framing, Beams and Longerons or Poles and Madriers. In general, the Categories referred to in this document are rough sawn.

Lightweight Framing is 2 « to 4 » thick (51mm to 102mm) and 2 « to 4 » (51mm to 102mm) wide lumber rough sawn or planed on four sides (S4S).

Joists and Structural Frames consists of rectangular elements with a thickness of 2 inches to 4 inches (51 mm to 102 mm), a width of 5 inches (127 mm) and more, rough sawn or planed on four sides ( S4S).

Beams and Girders are rough rectangular sawn or planed elements, 5 inches (127 mm) thick and larger with 2 inches (51 mm) wider than thickness.

Posts and Slips are rough square sawn or planed elements, 5 inches (127 mm) by 5 inches (127 mm) and a maximum width of 2 inches (51 mm) greater than the thickness.

Please contact a WRCLA dealer if you want more information to buy timber.


Timber specifications

Le thuya géant de toutes les catégories précédentes et les textures de surface sont fabriqués par des membres de l’Association du Thuya Géant en tant que Bois de Construction (WRCLA). Pour garantir que le thuya que vous spécifiez corresponde à la bonne catégorie et assurez-vous de spécifier une production par un membre WRCLA. Cette brochure vous aidera à sélectionner la bonne catégorie pour votre chantier. Ci-dessous, vous trouverez un exemple de spécification d’échantillon.

Spécifier le thuya géant pour les constructions en bois et les structures paysagères

Lors d’une commande, vous devrez fournir les informations suivantes :

Informations de spécification requisesSpécification d’échantillon
Espèces :
Thuya géant
Thuya géant WRCLA
Modèle de produit et utilisation prévue :
Les madriers sont utilisés dans de nombreuses structures comme les bâtiments commerciaux, industriels et résidentiels et dans les structures d’ingénierie et paysagères. Spécifiez la finition de la surface en choisissant raboté sur quatre faces (S4S), brut de sciage ou raboté à surface texturée.
Brut de sciage
Taille :
Spécifiez la taille du produit.
Scié pleine mesure 6 x 8
Catégorie :
La catégorie d’un produit Knotty correspond à sa qualité générale. Référez-vous à la documentation de spécification ou aux livres de règles de classification de la WRCLA pour consulter les catégories disponibles.
Bois de construction structurel Appearance Knotty
Classification agency paragraph:
To ensure that the product meets a written standard, a paragraph from the classification agency or an equivalent category must be referenced.
NLGA 130c
WCLIB 130cc
improved for its visual qualities
Specify whether the product should be green (not dried) or dried.
Surface to expose:
Specify the orientation of the application to help the supplier send you the right product for your job site.
Sawed face
In linear feet.
2000 linear feet
Veuillez noter que les unités de mesures affichées sur cette page sont en système Impérial. Si vous désirez des mesures en système Métrique, veuillez utiliser un outil de conversion adapté.
Veuillez noter que les normes, calibres et autres données mentionnées sur cette page sont basées sur les datas Nord-Américaines. Veuillez vous référer à vos ressources ou autorités locales si vous recherchez des données relatives à un pays spécifique.