Durability is a measurement of how long specific species of timber would last if a 50mm x 50mm cross section was left in the ground unprotected.
An untreated Oak beam
, which is classed as 'durable', for example, will last 15-25 years depending on environmental conditions.
The following scale of durability was outlined by TRADA, the Timber Research And Development Association.
||Average timber service life
||less than 5 years
||more than 25 years