Objective 20.01 Describe grades of lumber and plywood

Grades of lumber and plywood Hardwood or Softwood Hardwood: comes from deciduous trees such as oak, birch, walnut, maple, and hickory Softwood: comes from evergreen conifers such as pine, cedar, cypress, fir, and redwood

Grades of lumber and plywood Roughed or Dressed Rough or normal sized lumber is the actual size or full-dimension. A 2x4 is actually that size with rough surfaces Dressed or surfaced on a ll four sides lumber is smaller than rough lumber and is smooth A dressed 2x4 is actually 1 ¼” x 3 ½” A 1’ thick board is actually ¾” thick

Grades of lumber and plywood Select or Common Select lumber is free of knots and blemishes, and select grades are A, B, C, and D Common lumber is general-purpose wood and may have knots and blemishes Grade 1= may have sound, smooth knots upt to 2” Grade 2=used for flooring and framing and has large knots and blemishes Grade 3=loose knots or knotholes, used for shelving Grade 4 & 5=poor quality, temporary structures

Grades of lumber and plywood Plywood: made by gluing odd numbers of veneer (layers) of wood to make 4’x8’ or 4’x12’ sheets of different thickness Hardwood or softwood outside layers Exterior has waterproof glue Interior may or may not have waterproof glue

Plywood Veneer grades A=best, smooth, paintable, may have some neat repairs B=solid, some tight knots, splits, and repairs C=tight knots up to 1 ½”, knotholes up to 1” splits, discoloration and defects D=knots and knotholes up to 2 ½” splits

Plywood AC = exterior plywood with A face and C back AD = interior plywood with A face and D back OSB=Oriented Strand Board in the same sizes as plywood It is made from strands, flakes, or wafers sliced from small diameter logs and bonded with exterior glue under heat and pressure Engineered so that the wood strands are oriented, not randomly placed like wafer board

Plywood Particle board=manufactured sheets of wood made from ground up scrap wood, sawdust, and glue Shiplap=board with a rabbet cut on each edge Tongue and groove: have a tongue or lip on one edge and a groove on the other edge so that the lip of one side fits into the groove on another board.