the average life of timber used in exposed environment is
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Explanation:
Durability is expressed as one of four classes. The value for each species is based on trials of the resistance to both decay and termites of untreated heartwood in the ground. The classes are: (1) Class 1- Timber of the highest natural durability, expected to have a life greater than 25 years in the ground and greater than 40 years exposed above ground. (2) Class 2 - Timber of high natural durability, expected to have a life of about 15 to 25 years in the ground and 15 to 40 years exposed above ground. (3) Class 3 - Timber of moderate natural durability, expected to have a life of about 5 to 15 years in the ground and 7 to 15 years exposed above ground. (4) Class 4 - Timber of low durability, expected to have a life of 0 to 5 years in the ground and 0 to 7 years exposed above ground. The sapwood of all species is regarded to be Class 4.
Explanation:
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