General

3.3Timber preservation (natural solid timber)

This chapter gives guidance on meeting the Technical Requirements for the protection of natural solid timber against fungal decay and insect attack, dependent upon its use.

Definitions for this chapter

For the purposes of this chapter, the following definitions apply:

Durability to biological agents	Inherent resistance of a wood species or a wood-based material against wood decay organisms.
Heartwood	Inner zone of wood that, in the growing tree, has ceased to contain living cells or to conduct sap.
Sapwood	Outer zone of wood that, in the growing tree, contains living cells and conducts sap. (The durability of sap wood is minimal whatever the species).
Service situation	Situation of exposure of the wood element in use.
Softwoods	Are typically mixture of wood types including juvenile wood, and would contain a high percentage of sapwood, which may be difficult to distinguish from the heartwood and it is usually impractical and uneconomical to exclude it.
Use classes	Are based on differences in environment exposures that can make the wood or wood-based products susceptible to biological deterioration. Table 1 of BS 8417 summarizes the use class system and gives examples of typical service situations. Also see BS EN 335 for applications.
Wood species	Trade name according to EN 13556 which can on occasion include more than one botanical tree species.
Durability classes	Durability classes are systems of determining and classifying durability of wood species or wood-based materials to various wood destroying organisms based on test methods described in relevant EN Standards. The following grade scales are used depending on the destroying organisms: ■ A five-grade scale (DC 1-5) for decay basidiomycete fungi and soft rotting micro-fungi (Table 1 of BS EN 350 & expanded in Table 2 of this chapter) ■ A two-grade scale (DC D & S) for wood-boring beetles - Hylotrupes bajulus, Anobium punctatum etc (Table 2 of BS EN 350) ■ A three-grade scale (DC D, M & S) for termites and marine organisms (Tables 3 & 4 of BS EN 350)

Introduction

This chapter gives acceptable treatment schedules for the treatment of natural solid timber but does not cover:

products such as plywood and wood particle boards

the condition before the treatment

treatment process techniques, which is the responsibility of the organisation carrying out the operation.