Natural Durability Classification (Malaysia Standard)
Natural durability is the inherent resistance of heartwood timber to decay, fungi and insect. Natural durability doesn’t refer to the sapwood of tree, because the sapwood timber of all species has very poor durability .
The natural durability of a wood species is evaluated by a variety of standards. Malaysia has a unique standard for rating the natural durability of her lumbers.
In Malaysia, nutural durability ratings are obtained through “Grave Yard Test”. The test specimen is a stake of size 50 x 50 x 600mm . In the test, half of the length of
the stake is buried into the test grounds. The ratings are depended on the time when the timbers in the grounds becomes “Moderately decay and/or Moderately termite attack”.
In Malaysia, timbers are classified into four groups by their natural durability ratings:
Malaysian natural durability rating Service life in ground contact
Very durable More than 10 years
Durable 5 to 10 years
Moderately durable 2 to 5 years
Non-durable Less than 2 years
This rating is based on the testing of stakes imbedded in the ground in Malaysian tropical conditions . So you should not use this rating to predict the life expectancy for a lumber species used in different conditions and regions.