Specification and use of wood-based panels in exterior and high humidity situations

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Certain types of wood-based panels can be used in demanding exterior situations. However, they must be correctly specified, detailed, installed and maintained, in order to provide the desired performance and service life.


Exterior use covers a wide range of situations. They may be fully exposed to wetting by salt or fresh water or be more protected with a risk of occasional wetting, such as soffits under porches or lorry decks.


This Wood Information Sheet details the considerations which must be made when specifying wood-based panels for exterior use, in particular whether a preservative treatment or protective measure is required to extend service life.



  • Exterior exposure
  • Factors affecting performance
  • Specification
  • Durability of wood-based panels
  • Durability of plywood
  • Finishes
  • Design and workmanship
  • Maintenance
  • CE and UKCA marking


This Wood Information Sheet was revised in January 2021 following an extensive restructure. Reworked contents include: durability of plywood, use class 2 and treatments.


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 timberadvice@bmtrada.com.


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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