Timber durability is a measurement of how long certain 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' will last 15-25 years depending on environmental conditions.
The following scale of durability was outlined by TRADA, the Timber Research And Development Association.
|Durability||Class Designation||Average timber service life||Example Timber|
|5||Not durable||less than 5 years||American Ash|
|4||Slightly durable||5-10 years||American Popular Tulipwood|
|3||Moderately durable||10-15 years||American White Oak|
|1||Very durable||more than 25 years||-|