How do I specify preservative treatment for timber?

Reference EN 335 use classes to define the hazard level, then specify the treatment type and penetration requirements per EN 351-1. For example: 'Timber in Use Class 3.2 shall be pressure-treated with copper-based preservative to achieve minimum sapwood penetration of 6 mm and heartwood penetration of 3 mm.' Include the desired service life (typically 30 or 60 years) and whether the treatment must be colourless or can be tinted.

Reference EN 335 use classes to define the hazard level, then specify the treatment type and penetration requirements per EN 351-1. For example: 'Timber in Use Class 3.2 shall be pressure-treated with copper-based preservative to achieve minimum sapwood penetration of 6 mm and heartwood penetration of 3 mm.' Include the desired service life (typically 30 or 60 years) and whether the treatment must be colourless or can be tinted.

Why this matters

This question relates to How to Write a Timber Specification for Construction Tenders, which covers the broader topic in detail. Understanding this specific aspect helps architects, builders, and timber dealers make informed specification decisions.

For full context and additional technical detail, see our comprehensive guide:

→ How to Write a Timber Specification for Construction Tenders

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About this answer

This answer is part of the PuurModulair Knowledge Base — comprehensive timber specification guidance for architects, builders, and dealers across the UK, EU, and Scandinavia.