Plywood can be worked quickly and easily with
common carpentry tools. It holds nails well and
normally does not split when nails are driven close to
the edges. Finishing plywood presents no unusual
problems; it can be sanded or texture coated with a
permanent finish or left to weather naturally.
There is probably no other building material as
versatile as plywood. It is used for concrete forms, wall
and roof sheathing, flooring, box beams, soffits,
stressed-skin panels, paneling, shelving, doors,
furniture, cabinets, crates, signs, and many other items.
Softwood Plywood Grades
All plywood panels are quality graded based on
products standards (currently PS 1/74). The grade of
each type of plywood is determined by the kind of
veneer (N, A, B, C, or D) used for the face and back of
the panel and by the type of glue used in construction.
The plywood veneer grades are shown in table 3-7.
Many species of softwood are used in making
plywood. There are five separate plywood groups
based on stiffness and strength. Group 1 includes the
stiffest and strongest; group 5 includes the weakest
woods. A listing of groupings and associated woods
is shown in table 3-8.
Figure 3-37.-Standard plywood identification symbols.
GRADE/TRADEMARK STAMP. Construc-
tion and industrial plywood panels are marked with
Construction Panels. Grading identification
stamps (such as those shown in figure 3-37) indicate
the kind and type of plywood. The stamps are placed
on the back and sometimes on the edges of each sheet
For example, a sheet of plywood having the
designation A-C would have A-grade veneer on the
face and C-grade veneer on the back. Grading is also
based on the number of defects, such as knotholes,
pitch pockets, splits, discolorations, and patches in the
face of each panel. Each panel or sheet of plywood
has a stamp on the back that gives all the information
you need. Table 3-9 lists some uses for construction-
Industrial Panels. Structural and sheeting
panels have a stamp found on the back. A typical
example for an industrial panel grade of plywood is
shown in figure 3-38.
The span rating shows a pair of numbers
separated by a slash mark (/). The number on the left
indicates the maximum recommended span in inches
when the plywood is used as roof decking (sheeting).
The right-hand number applies to span when the
plywood is used as subflooring. The rating applies
only when the sheet is placed the long dimension
across three or more supports. Generally, the larger
the span rating, the greater the stiffness of the panel.
Figure 3-39 lists some typical engineered grades
of plywood. Included are descriptions and most
Figure 3-38.-Structural stamp.