Lumber, Plywood, and Other Wood Products - Carpenter's and Builder's Math, Plans, and Specifications - page 77

Ta ble 3-4 Lumber Grades

Grade Description Use

Select:
A High quality, practically

clear.

Suitable for natural finishes.

B High quality, generally

clear with a few minor
defects.

Suitable for natural finishes.

C Several minor defects. Adapted to high-quality

paint finish.

D A few major defects. Suitable for paint finishes.

Common:
No. 1 Sound and tight-knotted. Use without waste.

No. 2 Less restricted in quality

than No. 1.

Framing, sheathing,
structural forms where
strain or stress not
excessive.

No. 3 Permits some waste with

defects larger than in No. 2

Footings, guardrails, rough
subflooring.

No. 4 Permits waste, low quality,

with decay and holes.

Sheathing, subfloors, roof
boards in the cheaper types
of construction.

Common Lumber
Common lumber is suitable for general construction and utility pur-
poses and is identified by the grade names shown in Table 3-4.

Plywood
Plywood is a glued wood panel made up of relatively thin layers,
or plies, with the grain of adjacent layers at an angle, usually 90 ◦
(see Figure 3-2). The usual constructions have an odd number of
plies. The outside plies are called faces (or face and back plies), the
inner plies are called cores (or centers) , and the plies immediately
below the face and back are called crossbands . The core may be
veneer, lumber, or particleboard. The plies may vary as to number,
thickness, species, and grade of wood.
As compared with solid wood, the chief advantages of plywood
are its having properties along the length nearly equal to properties
along the width of the panel, its greater resistance to splitting, and
its form, which permits many useful applications where large sheets