What dimensional tolerances apply to structural timber?

EN 336 defines two tolerance classes for structural timber. Class 1 allows ±1 mm on thickness and width for dimensions up to 100 mm, and ±1.5 mm for dimensions over 100 mm.

EN 336 defines two tolerance classes for structural timber. Class 1 allows ±1 mm on thickness and width for dimensions up to 100 mm, and ±1.5 mm for dimensions over 100 mm. Class 2 allows ±1.5 mm and ±2 mm respectively. For most structural applications, Class 1 is appropriate. Length tolerance is typically ±5 mm or as specified by the designer. State the tolerance class explicitly in your specification.

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. All technical content is reviewed by qualified timber technologists before publication.