1. Objective 20.01
Describe grades of lumber and plywood

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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.