Building Construction Handbook, Eighth Edition

Characteristics and tolerances of GS and SS graded timber ~

Criteria GS SS

KAR: MKAR1/2 MKAR1/2
No margin
condition

TKAR1/2 TKAR1/3

Or:
KAR: MKAR > 1/2 MKAR > 1/2
Margin
condition

TKAR1/3 TKAR1/5

Fissures and
resin pockets:

Defects1 /2 timber thick-

ness

Defects1 /2 timber
thickness
Not through
thickness

< 1.5 m or 1/2 timber

length take lesser

< 1.0 m or 1/4 timber
length take lesser
Through
thickness

< 1.0 m or 1/4 timber

length take lesser

< 0.5 m or 1/4 timber

length take lesser

If at ends fissure length

maximum 2¾timber width

If at ends fissure

length < width of tim-

ber section

Slope of grain: Maximum 1 in 6 Maximum 1 in 10

Wane: Maximum 1/3 of the full
edge and face of the sec-
tion † length not limited

Resin pockets:
Not through
thickness

Unlimited if shorter than width of section otherwise
as for fissures
Through
thickness

Unlimited if shorter than

1/2 width of section other-

wise as for fissures

Growth rate
of annual
rings:

Average width or

growth < 10 mm

Average width or

growth < 6 mm

Distortion:
†bow < 20 mm over 2 m < 10 mm over 2 m
†spring < 12 mm over 2 m < 8 mm over 2 m
†twist < 2 mm per 25 mm < 1 mm per 25 mm
width over 2 m width over 2 m

Materials Testing---Softwood Timber Grading---4