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.
| Durability |
Class Designation |
Average timber service life |
Example Timber |
| 5 |
Not durable |
less than 5 years |
American Ash |
| 4 |
Slightly durable |
5-10 years |
Siberian Larch |
| 3 |
Moderately durable |
10-15 years |
Douglas Fir |
| 2 |
Durable |
15-25 years |
European Oak |
| 1 |
Very durable |
more than 25 years |
Teak |