Fissures and resin pockets ~ defects in growth. Fissures, also
known as shakes, are usually caused by separation of annual
growth rings. Fissures and resin pockets must be limited in
structural timber as they reduce resistance to shear and bending
parallel to the grain.
A + B = fissure
size
C = fissure
size
width
and face
thickness and edge
length
of
fissure
pith
Slope of grain ~ an irregularity in growth or where the log is not
cut parallel to the grain. If excessive this will produce a weakness
in shear. Measurement is by scoring a line along the grain of the
timber surface and comparing this with the parallel sides of the
section.
grain reasonably parallel
X
1
slope of grain = 1 in X
Insect damage ~ no active allowed. Wood-worm holes acceptable if
only nominal. Wood wasp holes not permitted.
Sapstain ~ acceptable.
Materials Testing---Softwood Timber Grading---2