Building Materials, Third Edition

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example, Type AA should have both surfaces of quality A, Type AB should have face of quality
A and the back of quality B and Type BB should have both the surfaces of quality B.
The thickness of plywood boards for general and structural purposes should be as given in
Table 4.6.

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Q2  QD2RD2SD2T R

S2  SD2TD2VD2W TD2W

U2  WD2IPD2ISD2IT IPD2IT

W2  IPD2ISD2ITD2IW ITD2IW

II2  IWD2PPD2PS IWD2PS

e˜2II2  y2

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The following tolerances on the nominal sizes of finished boards should be permissible:

Dimension Tolerance

General Purpose Structural Purpose

(a) Length +6 mm +6 mm

–0 mm –0 mm

(b) Width +3 mm +3 mm

–0 mm –0 mm

(c) Thickness

1. less than 6 mm ±10% ±10%


2. 6 to 9 mm
   }±5 %

±7 %

3. above 9 mm ±5 %
   (d) Squareness ± 0.2% 0
   (e) Edge straightness ±0.2% 0

Structural plywood panels are available in following sizes.
2400 × 1200 mm, 2100 × 1200 mm, 1800 × 1200 mm, 2400 × 900 mm, 2100 × 900 mm, 1800 × 900 mm.

e&——

1. It has good strength both along as well as across the grains.


2. The wood shrinks or swells more across the grains. Since plywood has cross-grained
   construction, the tendency to shrink or swell is reduced.


3. It has better splitting resistance due to the grains in adjacent veneers in cross direction as
   such nailing can be done very safely even near the edges.


4. Plywood can be curved into desired shapes.

…XThese are extensively used for partitions, ceilings, doors, concrete form work, plywood
boards, lamin boards (built-up boards with core strips up to 7 mm wide and 7 mm thick) and
block boards (built-up boards) etc.