Finishes for external timber

Date Published

17 August 2022

Document Type




Timber that has no protective finish will often weather to an attractive appearance. However, in many situations, it is necessary to specify a protective finish. Appearance is often the main reason for specifying a finish, but other characteristics are important too.

The technology behind protective finishes moves rapidly and the range of generic types and manufacturers’ variants is bewildering. Deciding whether to specify preservative, paint, varnish or stain is just the start.

This Wood Information Sheet (WIS) outlines the need for finishes, the different types of finishes as well as the performance of the various finishing types, helping specifiers to select the correct finishing coat for the job.

Key Information

Timber exposed to weather and not protected by some kind of finish will ‘weather’ and quite rapidly become bleached and grey.

There are four basic types of materials suitable for the exterior treatment and finishing of wood: preservatives, paints, varnishes and wood stains.

BS EN 927-1 offers a framework where coatings with specific appearance criteria can be matched to end use without compromising functionality.

Case studies

Walking into the new railway station at Abbey Wood, the immediate impression is of the elegant timber roof which arches over the interior, imparting a warm, natural quality to this large public space – more than 25 metres by 25 metres.

A dramatic timber canopy shelters the Constellations Bar, a new community space in The Baltic Triangle, between the Anglican cathedral and Queen’s Dock, a former industrial area in Liverpool which has evolved into a creative district.