The Commercial Timber Guidebook

USE CLASSES INFORMATION

Use Class

Principal Biological Agent

Typical Service Situation

Service Situation

Examples

All timbers in normal pitched roofs except tiling battens and valley gutter members. Floor boards, architraves, internal joinery, skirtings. All timbers in upper floors not built into solid external walls. Tiling battens, frame timbers in timber frame houses, timber in pitched roofs with high condensation risk, timbers in flat roofs, ground floor joists, sole plates (above DPC), timber joists in upper floors built into external walls.

Above ground, covered, permanently dry

Internal, with no risk of wetting

1

Insects

Above ground, covered (ie by a roof or other building component). Occasional risk of wetting Coated above ground, protected eg by a coating. Exposed to frequent wetting. If wood becomes wet, drying out may be delayed by a coating Uncoated above ground not protected. Exposed to frequent wetting

Internal, with risk of wetting

2

Fungi/insects

External, above damp proof course DPC coated

External joinery including roof soffits and fascias, bargeboards, cladding, valley gutter timbers, external load bearing timbers.

Fungi

3

Fence rails, gates, fence boards, agricultural timbers not in soil/manure contact and garden decking timbers that are not in contact with the ground.

External, above DPC uncoated

Fungi

Timbers in permanent

contact with the ground or below DPC. Timbers in permanent contact with fresh water. Cooling tower packing. Timber exposed to the particularly hazardous environment of cooling towers.

Fence posts, gravel boards, agricultural timbers in soil/manure, earth-retaining wals, poles, sleepers, playground equipment, motorway & highway fencing and garden decking timbers that are in contact with the ground. Lock gates and revetments. Cooling tower pacing (fresh water).

In contact with ground or fresh

4

Fungi

water. Permanently exposed to wetting

Permanently exposed to wetting by salt water

All components in permanent contact with sea water

Marine borers, fungi

Marine piling, piers and jetties, dock gates, and cooling tower packing (sea water)

5

DURABILITY

3 7

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