Multi-Layer Structure
Generally consists of 3, 5 or 7 layers.
CLT guide
What is CLT? A comprehensive guide to Cross-Laminated Timber
Cross-Laminated Timber — CLT — is a building material that is revolutionizing wood construction technology and coming to the fore in sustainable construction. Thanks to properties such as high strength, flexibility and environmental sustainability, it is increasingly preferred in modern architecture.
Technical definition
Cross-Laminated Timber (CLT) is a multi-layer, structural panel system formed by laminating wood layers perpendicular to each other. Each layer is placed perpendicular to the previous one; this enhances the material's dimensional stability, strength and rigidity.
Reasons to choose CLT include its high strength, light weight, flexibility and sustainability. CLT panels can be used as an alternative to traditional building materials such as concrete and steel and offer environmental advantages with a lower carbon footprint.
1. Definition and features of CLT
High Strength
Cross-laminated layers increase load-bearing capacity.
Dimensional Stability
Resistant to moisture and temperature changes.
Flexibility
Offers flexibility in design and application.
2. CLT production process
The production of CLT panels is a process that requires high precision and quality control. The production stages are explained in detail below.
Wood Selection and Preparation
- Wood Type: Generally softwoods such as spruce, pine or fir are used.
- Drying: Wood lamellas are kiln-dried to bring moisture content to the 12% ± 2 level.
- Grading: Lamellas graded mechanically and visually are selected according to quality standards.
Bonding and Lamination
- Finger Joints: Wood pieces are joined with finger joints to create long lamellas.
- Adhesive Application: Formaldehyde-free, eco-friendly polyurethane adhesives are used.
- Layer Placement: Each layer is placed perpendicular to the previous one.
- Pressing: Panels are laminated by pressing under high pressure and temperature.
Cutting and Processing
- CNC Processing: Panels are precisely cut to the desired dimensions and shapes on CNC machines.
- Surface Treatments: Surface sanding and protective coatings are applied when needed.
Quality Control and Certification
- Tests: Produced panels are subjected to strength, flexibility and durability tests.
- Certification: CLT panels are certified for compliance with national and international standards.
3. Technical properties and durability of CLT
Strength and Durability
- High Load Capacity: The cross-laminated structure efficiently carries both vertical and horizontal loads.
- Modulus of Elasticity: A high modulus of elasticity provides a wide application range in structural design.
- Dimensional Stability: Minimizes deformations caused by moisture and temperature changes.
Fire Resistance and Thermal Performance
- Fire Resistance: Thick wood sections char at the surface during a fire, protecting the interior.
- Thermal Conductivity: Energy efficiency with a low thermal conductivity value (λ = 0.12 W/m·K).
- Heat Capacity: Interior temperature stability through high heat capacity (c = 1.60 kJ/kg·K).
Acoustic Performance
- Sound Insulation: CLT panels reduce sound transmission thanks to their solid mass.
- Vibration Control: The natural properties of wood absorb vibration and noise.
4. Advantages of CLT
Eco-Friendly and Sustainable
- Renewable Resources: Wood is a renewable resource through sustainable forest management.
- Low Carbon Footprint: Wood absorbs CO₂ from the atmosphere as it grows and stores carbon.
- Waste Reduction: Minimum waste in production; waste can be recycled.
Fast and Easy Assembly
- Prefabrication: Panels are produced at the factory and quickly assembled on site.
- Labor Efficiency: Requires less labor and equipment, shortening construction time.
- Weather Independence: Fast assembly reduces weather-related delays.
Cost Efficiency
- Lower Foundation Costs: Lighter structure → lower foundation loads and costs.
- Shorter Construction Time: Lower total project costs.
- Energy Savings: High thermal performance → lower operating costs.
Aesthetics and Design Flexibility
- Natural Appearance: The natural aesthetics of wood create a warm atmosphere.
- Design Freedom: Can be produced in various shapes and sizes.
5. CLT applications
Multi-Storey Buildings
Wooden structures up to 10 storeys thanks to light weight and strength. Example: the 85.4 m Mjøstårnet building.
Residences
Prefabrication → fast completion. High insulation → energy savings.
Industrial and Commercial Buildings
Wide spans with fewer columns/beams required. Flexibility in interior layout.
Education and Public Buildings
Healthy interior air quality; natural wood look enhances user experience.
Seismic Resilience
CLT's flexibility and energy-absorbing capacity provide resistance to earthquake loads.
6. Environmental contributions of CLT
Carbon Storage
- Carbon Capture: Wood structures store atmospheric CO₂.
- Carbon Neutrality: Contributes to the construction sector's carbon-neutral targets.
Energy Efficiency
- Thermal Insulation: Low thermal conductivity reduces heat loss.
- Reduced Operating Costs: Long-term cost savings.
Eco-Friendly Production
- Low Energy Consumption: Less energy compared to steel and concrete.
- Recycling and Reuse: Wood materials can be recycled.
7. The future of CLT and innovations in construction
Sustainability Trend
- Green Buildings: Environmental awareness drives demand for sustainable materials.
- Carbon Emissions: Government policies encourage low-carbon materials.
Technological Advances
- Production Technologies: CNC and robotic systems deliver precision and efficiency.
- New Materials: Hybrid structures and wood composites expand application areas.
Market Growth
- Global Demand: Global demand for CLT is rising rapidly.
- Investment: Investment in the construction sector improves CLT production capacity and technology.
Technical specifications table
| Property | Value |
|---|---|
| Wood Type | Spruce · Pine · Fir |
| Number of Layers | 3, 5, 7 or more |
| Layer Thickness | 20 · 30 · 40 mm |
| Panel Thickness | 60 – 400 mm |
| Maximum Dimensions | Width: 4.8 m · Length: 20 m |
| Density | 450 – 500 kg/m³ |
| Thermal Conductivity (λ) | 0.12 W/(m·K) |
| Heat Capacity (c) | 1.60 kJ/(kg·K) |
| Moisture Content | 12% ± 2 |
| Fire Resistance | R30 – R90 |
| Acoustic Performance | Rw = 30 – 55 dB |
Frequently asked questions
CLT is a building material formed by laminating wood layers perpendicular to each other. Thanks to its high strength, light weight and environmental sustainability, it has become important in modern construction projects.
Yes. CLT structures are naturally fire-resistant. Thick wood sections char at the surface during a fire, protecting the interior and helping preserve structural integrity for a certain period.
CLT is produced from renewable wood resources obtained from sustainable forests. It reduces the carbon footprint through low energy consumption in production and carbon storage.
CLT panels are generally produced in thicknesses from 60 mm to 400 mm and in sizes up to 4.8 m wide and 20 m long. Dimensions may vary by project requirements.
Yes. CLT's flexible and light structure provides resistance to earthquake loads. Its seismic resilience allows safe construction in earthquake zones.
CLT's initial cost may be slightly higher than traditional materials. However, factors such as fast construction time, low labor costs and energy efficiency reduce total project costs and provide an economic advantage.
CLT panels are protected from external factors through appropriate surface coatings and detailing. Regular maintenance and inspection extend the life of the structure and preserve its performance.
CLT can be used in a wide range from residences to multi-storey buildings, from industrial structures to bridges. Its design flexibility suits different architectural projects.