Softwood lumber is classified by government standards as Yard, Structural, and Factory and Shop Lumber, which is used in smaller pieces for remanufacturing, such as door rails and stiles, or in wood ladders.
Yard refers to lumber used in general construction, such as boards, laths, and wood siding. The lumber is graded visually:
• C Select is almost free of all defects; used for cabinets and shelving
• D Select is almost free of defects but may have small knots less than the size of a dime
• 1 Common contains knots that are small, tight and won’t fall out, such as pine
• 2 Common contains slightly larger knots; may be used for shelving.
• 3 Common contains larger knots and is suitable for fencing or crates.
Structural Lumber is used in framing buildings as posts, beams, studs, rafters, joists sill plates and wall plates. The size chosen will be determined by its use and strength or bendability. 2X4; 2X6; 2X8; 2X10; 2X12; 4X4; 4X6; 4X8; 6X6; and 8X8 are the sizes produced as dimensional lumber.
• Machine grading measures stiffness or density to provide information the builder needs to construct appropriately. Moisture content and species are also noted as well as the mill producing the lumber. Species is included in the grading. The following are grades for Western Wood Products and Southern Yellow Pine, although SYP are graded for the first three only.
• Structural Light Framing (SFL) is 2” to 4” thick; 2” to 4” wide grades Select Structural, No. 1, No. 2 No. 3 used in structural applications where highest design values are needed in light framing sizes.
• Light Framing (LF) is 2” to 4” thick, 2” to 4” wide grades Construction, Standard, Utility used where high strength values are not required, such as wall framing, plates, sills, cripples, blocking, etc.
• Stud2” to 4” thick; 2” and wider graded Stud is an all-purpose grade for studs including bearing walls.
• Structural Joists and Planks (J&P) are graded as Select Structural, No. 1, No. 2 and No.3.
• Beams and Stringers are 5” and thicker, width more than 2” greater than thickness are graded Dense Select Structural, Dense No.1 and No. 2 (Doug Fir or Doug Fir-Larch only); Select Structural, No. 1 and No.2 used for beams and stringers when sizes are larger than 4” nominal thicknesses are required.
• Post and Timbers 5” X 5” and larger; width not more than 2” greater than thickness Dense Select Structural, Dense No.1 and No. 2 (Doug Fir or Doug Fir-Larch only); Select Structural, No. 1 and No.2 are used for vertically loaded applications where sizes larger than 4” nominal thickness are required.
• Structural Decking 2” to 4” thick, 4” to 12” wide Selected Decking used where appearance of the best face is important; 2” to 4” thick, 4” to 12” wide. Commercial Decking is used when appearance is not of primary importance.
• Softwood Boards are cut less than 2” thick and 5” deep in various lengths used for moulding, shelving and woodworking projects.
Timbers are milled 5” thick or greater and used as beams, stringers, posts, caps, sills, girders, or purlins.
Treated lumber is milled to dimensional standards for use in outdoor projects such as decks, sheds, etc. Decking is milled with curved edges for use as deck flooring and railing. Treated with preservatives described above, deck boards are pine milled to about 1-inch thick by 5-1/2 inches. Some deck boards may be slightly thicker.