Assessing the risk and
consequences of failure
Decisions about the need for treatment must also take into consideration the risk and consequences of failure. One use class can cover a range of components yet the risk and consequences of failure can vary from one to another. Each component should be assigned a “service factor code” to assess the need for preservative treatment see table 2 below.
An alternative to using preservative pre-treated wood is to use modified wood or a species with a natural durability classification suitable for the use class. Details of appropriate species classified by durability and use class suitability can be found in the WPA Wood Preservation Specification Manual
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Service factor codes relating to need for preservation (Source:BS8417) |
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Service factor code |
Description of risk and consequences of failure |
Need for Preservation |
|
A |
Negligible risk of failure |
Unnecessary |
|
B |
Where risk of failure is low and preservation can be regarded as an insurance against cost of repairs, and/or where replacement of timber or remedial action is not difficult or expensive. |
Optional |
|
C |
Where risk of failure is high and/or where replacement of timber or remedial action is difficult and expensive. |
Desirable |
|
D |
Where risk of failure is very high and/or where failure of timber components would result in serious danger to structure or persons |
Essential |
