How do appearance grades differ from structural grades?

Structural grades (C16, C24, C30 etc.) define mechanical properties for load-bearing applications — they say nothing about appearance. Appearance grades (Nordic A, B, C, D; German S/F/K; British O/B/U) classify timber by visual quality for non-structural or dual-purpose applications.

Structural grades (C16, C24, C30 etc.) define mechanical properties for load-bearing applications — they say nothing about appearance. Appearance grades (Nordic A, B, C, D; German S/F/K; British O/B/U) classify timber by visual quality for non-structural or dual-purpose applications. A piece of timber can be both structurally graded (C24) and appearance graded (Nordic B) simultaneously. For exposed structural applications, both grades must be specified: e.g., 'C24 structural grade, Nordic B appearance' ensures the timber is both strong enough and visually acceptable.

Why this matters

This question relates to European Timber Grades Explained: Nordic, German & British Systems, 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:

→ European Timber Grades Explained: Nordic, German & British Systems

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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.