Is larch or thermowood better for decking?

Thermally modified timber (thermowood) generally outperforms European Larch for decking because: it has higher durability (DC 1–2 vs DC 3), better dimensional stability (less cupping and twisting), more uniform colour, and lower moisture uptake. However, thermowood is more brittle (requires pre-drilling for all fixings) and typically 30–50% more expensive than larch.

Thermally modified timber (thermowood) generally outperforms European Larch for decking because: it has higher durability (DC 1–2 vs DC 3), better dimensional stability (less cupping and twisting), more uniform colour, and lower moisture uptake. However, thermowood is more brittle (requires pre-drilling for all fixings) and typically 30–50% more expensive than larch. Larch offers good value with acceptable durability for budget-conscious projects where some maintenance is accepted.

Why this matters

This question relates to Timber Decking Specification: Durability Classes & Species Selection, 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:

→ Timber Decking Specification: Durability Classes & Species Selection

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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.