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Timber Treatments – Looking After Timber in Your Home and Garden

It is beneficial to understand the importance of timber treatment within internal and external timbers, however, it is not always clear what treatment options are available.

There are two types of preservative treatment available, the first being Vacsol Aqua (Vac-Vac). This is a treatment required for timbers used internally as Vacsol provides long-term performance for low-medium risk interior and exterior construction and joinery timbers used above damp-proof course levels. Secondly, Tanalith E is used on external timbers and can be treated to a 15-year silver service life or a 30-year gold service life.

Timber Species

Preservative treatment of timber is important because it significantly extends the service life of external timbers, by protecting it against all forms of wood decay and insect attack. This is particularly useful when your garden furniture is outside all year round. Any timber being used externally is recommended that it is pressure treated and as all timber species have their own characteristics; some only suit certain end uses, and some are easier to treat than others.

Timber Preparation

All harvested timber has a moisture content (a measurable level of water within the wood) which is important to measure and regulate in order for the preservative to sufficiently penetrate the timber during treatment and avoid the timber splitting during service.

From a treatment point of view, the most economical way of achieving the correct moisture content is by natural air-dry methods.

Timber Treatment

The level of pressure treatment given to the timber depends on its eventual end use. Within the industry, there are Use Classes (UC) which define the end use of the timber and the appropriate level of preservative protection required. UCs range from UC1 (lowest level of protection required – such as internal building timbers) to UC4 (highest level of protection required – such as external timbers in ground contact).

An idea of which level is needed is shown here:

Use Class Summary

1 – INTERNAL, dry e.g. upper floor joists

2 – INTERNAL, risk of wetting e.g. tiling battens

3.1 –COATED, coated above ground e.g. decorated cladding

3.2 – UNCOATED, uncoated above ground e.g. fence rails­


4 – HIGHWAYS AGENCY TIMBERS – higher performance specification than normal Use Class 4 treatments.

This blog was provided by Bond Timber