Timber Construction: Fundamentals

Timber Construction: Design-to-Production Fundamentals

Introduction

The content covers fundamental aspects of timber construction, including material properties, construction approaches, structural detailing, cost calculation, and practical applications, with case studies highlighting best practices.

Differences to Other Materials

Key Material Properties

Timber possesses unique properties that distinguish it from other construction materials such as steel and concrete. The following table summarizes key material characteristics:

Property	Steel (S235)	Concrete (C30/37)	GLT 24h Spruce	GLT 75 Beech	LVL Beech	LVL Spruce (Kerto-s)	CLT Spruce/Larch
Density (kg/m³)	7,850	2,300	380	800	730	480	480
Young Modulus (N/mm²)	210,000	34,077	11,600	16,800	16,800	13,800	12,000
Strength-to-Weight Ratio	High	Medium	Very High	High	High	Medium	Medium

Timber offers superior strength-to-weight ratios compared to steel and concrete, making it advantageous for lightweight and resilient structural systems.

Anisotropy in Timber

Timber is anisotropic, meaning its properties differ along various directions. This aspect significantly influences load-bearing capacity and structural alignment. For optimal performance, load-bearing should be unidirectional, and design configurations should align with the material’s natural orientation.

Intelligent Timber Components

The use of CNC technology enhances the precision and functionality of timber components, allowing for advanced detailing such as cut-outs for mechanical, electrical, and plumbing (MEP) integration, facilitating installation and reducing site labor.

Resistance and Insulation Properties

Timber naturally resists thermal transfer, minimizing the occurrence of cold bridges and offering superior insulation performance. Additionally, engineered timber elements are designed to meet fire safety standards while maintaining structural integrity.

Structural Typologies and Rules of Thumb

Efficient timber structures depend on suitable span-to-height ratios. The following guidelines are recommended:

Structural Element	Span-to-Height Ratio
Beam Supported Slab	1/15
Rib Slab	1/25
Box Slab	1/30
Full Wall Glulam	1/20
Truss	1/15
Columns (Slenderness)	1/25
Arches (Total Height)	1/10
Shells (Total Height)	1/6

Detailing and Connection Systems

Steel-Wood Connections

Steel is generally embedded within timber to prevent fire hazards, reduce condensation, and maintain symmetrical load distribution. Steel should be used where high forces or ductility requirements are present.

Wood-Wood Connections

Various types of wood-wood connections are utilized in timber construction:

• Pin Connection: Allows rotational freedom while maintaining shear transfer.

• Ridged Connection: Rigid and fixed, suitable for resisting both tension and compression forces.

• Heavy Ridged Connection: Suitable for high load-bearing scenarios, utilizing multiple pins and enhanced reinforcement.

Cost Calculation and Project Planning

A model-based evaluation helps optimize construction methods, cost management, and logistics planning. The following factors influence the total cost:

• Material procurement

• CNC machining and pre-assembly

• Logistics and site assembly

• Health, safety, and weather protection measures

Project Planning Considerations

Project timelines should integrate both off-site and on-site production, with careful coordination to leverage local materials and maximize efficiency.

Conclusion

Timber construction continues to evolve, driven by advancements in engineered wood products and CNC technology. The strategic use of timber offers not only sustainable building practices but also innovative design opportunities, ensuring robust, resilient, and aesthetically appealing structures.