Finishes for external timber

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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.



  • The need for finishes
  • Types of exterior finish
  • Considerations for hardwoods
  • Considerations for panel products
  • Selection of coatings
  • Common coating faults and how to avoid them


This Wood Information Sheet was reviewed in April 2022. Minimal amendments have been made.


For queries about this technical document, please get in touch with its authors via BM TRADA’s Technical Helpline on +44 (0)1494 569601 or email


A paper/digital copy of this Wood Information Sheet is available in the BM TRADA Bookshop, which also hosts additional specialist timber publications.

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