Preservative types and processes


High Pressure Treatments

These new generation products have now been in use for many years and are designed to match the performance expected from current regional European standards. Treatments requirements vary depending upon the timber species being used, the make-up of the timbers and the eventual end use of the timber component. High pressure treatments are carried out in purpose designed treatment cylinders and involve proven treatment cycles of applying controlled vacuum and pressure periods to drive the wood preservative deep into the structure of the timbers.

The treated timbers are initially pale green in coloration, slowly weathering to a warm honey brown and eventually to a natural silver grey. Colorants and water repellents can be added to the treatments to provide treated timber options.

These treated timbers are suitable for use in Use Classes 1, 2, 3 coated, 3 uncoated and 4.

Low Pressure Treatments

Low pressure treatments were developed and introduced in the 1960’s as a more focussed option for construction and joinery timbers. Utilising a faster double vacuum cycle the treatment provides an envelope of protection around the timber components and retain the original dimensions of the timber – an important factor for close tolerance timber components.

Treatments leave the appearance of the treated timbers virtually unchanged although colour dyes can be added to the treatments, if required, to aid treatment identification. Water repellents can also be added to provide extra dimensional stability to the treated timbers.

These treated timbers are suitable for use in Use Classes 1, 2, and 3 coated. They should only be used above damp proof course in buildings and when used externally (Use Class 3 coated) they must be protected with an appropriate and well maintained decorative coating.

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