Grades

Plank decking is available in two grades, Select and Commercial, based on the appearance of the best face as shown in the Table 1 below.

Table 1: Plank Decking Grades
Size
Grade Principal Uses Metric Imperial(actual)
Select For roof and floor decking where   strength and fine appearance are required. 38, 64 and 89mm thick
127mm and wider
1-1/2″, 2-1/2″, and 3-1/2″ thick 5″ and wider
Commercial For roof and floor decking where strength is required but appearance is not so important. Grade contains pieces that do not meet Select Grade requirements. 38, 64 and 89mm thick
127mm and wider
1-1/2″, 2-1/2″, and 3-1/2″ thick 5″ and wider

Select grade is used for high quality construction where high strength and fine appearance for exposed locations are desired.

Commercial grade contains more growth characteristics and more manufacturing defects than Select grade. Commercial grade is chosen when appearance and strength are less critical such as in industrial buildings.

The permitted characteristics for Select and Commercial grades are shown in Table 2 below.

Table 2: Permitted Characteristics for Select and Commercial Grade Plank Decking
Category Permitted Select Grade Characteristics Permitted Commercial Grade Characteristics
Growth medium stained wood stained wood
small holes, equivalent to chipped knots holes, 25mm (1″)
slope of grain not to exceed 1 in 10 slope of grain not to exceed 1 in 8, full length
medium bark pockets bark or pitch pockets
sound and tight knots on exposed face unsound wood and/or peck not exceeding approximately 1/3 of any face
knots well spaced, not larger than approximately 60mm (2-3/8″) in diameter permitted both wide faces for 38 x 127mm (2″ x 6″ nom.) and 83mm (3-1/4″) for 38 x 178mm (2″ x 8″ nom.) knots well spaced, not larger than approximately 73mm (3″) permitted on both wide faces for 38 x 127mm (2″ x 6″ nom.) and 95mm (3-3/4″) for 38 x 178mm (2″ x 8″ nom.)
in occasional pieces, unsound knots, if tight and not exceeding 38mm (1-1/2″) in diameter, are permitted if medium checks not through the piece and do not exceed 2 in a 4m (13′) length or equivalent smaller. shake not serious
occasional crook medium
spike and narrow face knots are permitted if judged to have no more effect on strength than other knots. spike and narrow knots are permitted if judged to have no more effect on strength than other knots.
chipped and/or broken out knots not larger than approximately 19mm (3/4″)in diameter are permitted if not through the piece and do not exceed 2 in a 4m (13′) length. chipped and/or broken out knots or portions of knots not larger than approximately 38mm (2″nom.) in diameter are permitted if not through the piece.
on unexposed face and edges, hit and miss skips or wane approximately 1/3 of the face width, pecky spots in narrow streaks, skips 10 percent of exposed face in occasional pieces and other characteristics not interfering with the intended use are permitted. on unexposed face and edges wane approximately 1/3 of the face and other characteristics not interfering with the intended use are permitted.
Seasoning medium checks checks
occasional short splits splits approximately 1/6 of length
occasional light crook wane approximately 1/6 of the face width
Manufacturing tongue 2mm (1/8″) narrow on occasional pieces tongue 2mm (1/16th) narrow
medium torn grain torn grain
hit and miss skips hit and miss skips