composite / Timber-Based Composite / Cross-Laminated Timber

Radiata Pine, cross-laminated timber (CLT) panel (60mm, 80mm, 100mm, 120mm, 140mm, 160mm, 200mm, 280mm)

Mass-timber structural panels made from cross-laminated radiata pine, offering high stiffness, dimensional stability, carbon-negative embodied carbon, and predictable fire performance through sacrificial charring. The flagship product of Australian mass timber construction.

Atlas code

COM-TBC-CLT-001

compositetimber-basedCLTcross-laminated-timberradiata-pinemass-timberstructural

Radiata Pine, cross-laminated timber (CLT) panel (60mm, 80mm, 100mm, 120mm, 140mm, 160mm, 200mm, 280mm)

At-a-glance signals

Overview

Executive summary

Cross-laminated timber (CLT) panels are structural mass-timber elements manufactured by bonding layers of radiata pine boards at alternating 90-degree angles using structural adhesives (MDI or PUR). The cross-lamination creates a bi-directional panel with high stiffness, dimensional stability, and predictable structural performance for walls, floors, and roofs. XLam Australia (Wodonga, VIC) is the dominant domestic manufacturer, producing panels from 60 mm to 280 mm thickness in widths up to 2.95 m and lengths up to 13.5 m. CLT enables rapid, precision-prefabricated construction with reduced wet trades and lower site waste than conventional concrete or steel framing.

Best when…

Carbon-negative embodied carbon stores biogenic CO2 for building lifetime
Rapid prefabricated construction — 20–30% faster structure than concrete equivalent
Lightweight (500 kg/m³) reduces foundation loads and seismic mass
Excellent dimensional stability across both panel axes
Predictable fire performance through sacrificial charring at 0.65 mm/min
Biophilic exposed timber improves occupant wellbeing and satisfaction
Dry construction reduces wet trades and site waste
High structural efficiency: good strength-to-weight ratio
Renewable resource from certified plantation forests (FSC/PEFC)
NCC-compliant to 25 m height (8 storeys) under DTS pathway

Top advantages

01 Carbon-negative embodied carbon stores biogenic CO2 for building lifetime
02 Rapid prefabricated construction — 20–30% faster structure than concrete equivalent
03 Lightweight (500 kg/m³) reduces foundation loads and seismic mass
04 Excellent dimensional stability across both panel axes
05 Predictable fire performance through sacrificial charring at 0.65 mm/min

Top limitations

01 Combustible — requires careful fire engineering and may need encapsulation
02 Moisture sensitive — panels must be protected on site during construction
03 Higher material cost than concrete slab or steel deck equivalents
04 Limited domestic manufacturing capacity creates potential supply constraints
05 Acoustic flanking paths through rigid CLT connections require careful detailing

Technical

Physical ·9

Density: 500 kg/m3 Mean panel density at 12% equilibrium moisture content. XLam Australia product data sheet.
Specific gravity: 0.5 Specific gravity of radiata pine at 12% MC relative to water.
Porosity: 40-50 % Approximate porosity of radiata pine wood cell structure. Not a primary design parameter for CLT panels.
Water absorption: Hygroscopic — equilibrates to ambient RH % by weight Timber is hygroscopic. Radiata pine will absorb moisture to equilibrium with ambient RH. Panels exposed to rain on site can gain 5–15% MC, causing swelling and checking. Protective wrapping is mandatory during construction.
Hardness: 2200 Janka Radiata pine face veneer Janka hardness. CLT panels are not typically rated by Janka hardness as a structural product; this reflects the face layer species.
UV resistance: Low (uncoated) / Good (with UV-stabilising coating) Exposed CLT will grey and surface-check under UV without coating. UV degrades lignin causing surface silvering within 6–18 months. Penetrating UV stabilisers or opaque coatings are required for exposed external applications. Internal exposed CLT is unaffected.
Chemical resistance: Moderate — resistant to dilute acids, susceptible to strong alkalis and concentrated mineral acids Timber has good resistance to dilute acids and many organic solvents. Susceptible to concentrated mineral acids, strong alkalis, and oxidising bleaches. MDI/PUR adhesive bonds are resistant to water and most solvents. Not suitable for prolonged immersion.
pH tolerance: 4.5-5.5 pH Wood is slightly acidic. Radiata pine pH approximately 4.5–5.5. Contact with reactive metals (zinc, uncoated steel) should be avoided without barrier treatment.
Surface roughness: 1-15 μm Ra Planed / sanded CLT face layer. Industrial finish (planed, not sanded) Ra 5–15 μm. Fine sanded architectural finish Ra 1–5 μm.

Mechanical ·7

Tensile strength: 16 (parallel to grain, F8 characteristic) MPa Characteristic tensile strength parallel to grain (f't) for radiata pine F8 laminate: approximately 16 MPa. Tensile strength perpendicular to grain is very low (0.5–1.0 MPa) and cross-grain tension must be avoided. CLT cross-lamination does not significantly improve perpendicular tensile strength.
Compressive strength: 25 (parallel to grain) / 5.5 (perpendicular to grain) MPa Characteristic compressive strength parallel to grain (f'c) for radiata pine F8 laminate: 25 MPa. Compression perpendicular to grain (f'p): approximately 5.5 MPa. Wall panels under axial load are typically governed by stability (buckling) rather than material crushing strength, particularly for slender panels. Design per AS 1720.1.
Flexural strength: 30 (F8 characteristic, major axis) MPa Characteristic bending strength (f'b) for radiata pine F8 laminate: 30 MPa. CLT panel bending capacity (major axis): 5-ply 175 mm panel approximately Mrd = 25–35 kNm/m depending on configuration and grade. Minor axis bending capacity is lower due to cross-lamination reducing effective section. Design per AS 1720.1-2010 reduced cross-section method.
Shear strength: In-plane: 3.5-5.0; Rolling shear: 1.0-1.5 MPa In-plane shear strength (panel shear): approximately 3.5–5.0 MPa for 5-ply CLT. Rolling shear (between cross layers, governing for CLT floors): 1.0–1.5 MPa characteristic. Rolling shear is the critical shear mode for CLT floor design under AS 1720.1 / EN 16351. XLam product data.
Poisson's ratio: 0.43-0.51 Poisson's ratio for radiata pine parallel to grain (LR plane). Not typically a governing design parameter for CLT panels; included for FEA modelling. Values: νLR ≈ 0.43, νLT ≈ 0.47, νRT ≈ 0.51.
Impact resistance: Impact sound Ln,w ~75-80 dB bare; 48-55 dB with floating floor system J/m² Impact sound insulation (floor): Bare CLT floor Ln,w approximately 75–80 dB. With floating screed and soft floor finish, Ln,w 48–55 dB achievable to meet NCC requirements for Class 2 buildings (L'n,w ≤ 62 dB). Structural impact resistance: timber has good toughness; panels resist localised impact loads well.
Creep resistance: Moderate — creep is a design consideration for long-span CLT floors; kdef = 0.8 (SC1) Timber exhibits visco-elastic creep, particularly under sustained load and elevated MC. CLT floor creep factor (kdef) per EN 1995-1-1: approximately 0.8 for Service Class 1 (dry interior). Long-term deflection = instantaneous deflection × (1 + kdef). Creep deflection must be verified for floor serviceability under AS 1720.1 and project-specific deflection limits.

Sustainability & Health

Embodied carbon & energy ·7

Embodied carbon: -492 kg CO2-eq/m3 XLam Australia EPD GWP (biogenic carbon included, cradle-to-gate): approximately -492 kg CO2-eq/m³. This reflects the biogenic carbon stored in the timber (approximately -700 to -800 kg CO2-eq/m³ sequestration) offset by fossil fuel processing emissions (approximately +60–80 kg CO2-eq/m³). Biogenic carbon is released at end of life if burned; retained if material is reused or sent to landfill. IPCC and EN 16449 recommend reporting both fossil and biogenic GWP separately for transparency.
Carbon footprint: -0.98 (including biogenic) / +0.12-0.16 (fossil only) kg CO2-eq/kg Including biogenic carbon storage: approximately -0.98 kg CO2-eq/kg (carbon negative). Fossil GWP only (excluding biogenic sequestration): approximately +0.12–0.16 kg CO2-eq/kg. Compare: concrete ~0.15, structural steel ~1.5–2.5 kg CO2-eq/kg.
Embodied energy: 700-900 (fossil, non-renewable primary energy) MJ/m3 Cradle-to-gate embodied energy (non-renewable primary energy) for radiata pine CLT: approximately 700–900 MJ/m³ (fossil fuels; AusLCI / Ecoinvent data). Total primary energy (including biogenic wood energy from sawmill residues): approximately 3,000–4,000 MJ/m³. Much lower than concrete (~1,500 MJ/m³ fossil) or steel (~60,000 MJ/tonne).
Water footprint: 200-500 L/m³ Plantation radiata pine water consumption: predominantly rainfall in plantation, minimal irrigation. Manufacturing water use (gluing, pressing) approximately 50–150 L/m³ of panel. Total water footprint approximately 200–500 L/m³ — substantially lower than concrete (approximately 200 L/m³ excluding aggregate washing) and aluminium (approximately 90,000 L/tonne).
Recycled content: 0 % Standard CLT panels use virgin plantation radiata pine laminations; recycled timber is not used due to dimensional and structural consistency requirements. Recycled content is approximately 0%.
Renewable content: 98-99 % Timber is 100% renewable (plantation-grown radiata pine). Adhesive (MDI/PUR) is petrochemical-derived: approximately 1–2% of panel mass. Net renewable content of CLT panel approximately 98–99% by mass.
Circular score: 7 /10 CLT panels can be disassembled and reused if mechanical connections (screws, bolts) are used rather than adhesive connections. Deconstruction and reuse has been demonstrated in pilot projects in Europe. In Australian practice, structural reuse is uncommon but increasing. Panel waste from CNC cutting can be chipped for biomass or MDF feedstock. Score reflects good potential but limited current Australian end-of-life infrastructure.

Compliance & Fire

Fire performance ·6

Combustibility class: Combustible (AS 1530.1) / EN 13501-1: D-s2,d0 Combustible material under AS 1530.1. Not classified as non-combustible. NCC provisions for combustible construction in Class 2–9 buildings require sprinkler system (AFSS) per AS 2118.1 and encapsulation of CLT to 30/30/30 FRL with non-combustible lining (e.g., 2 × 13 mm Type X plasterboard) in buildings above 3 storeys, unless a Performance Solution is used. EN 13501-1 classification: D-s2,d0 for untreated radiata pine CLT.
Fire resistance level: 30/30/30 to 120/120/120 depending on thickness and loading minutes Achieved FRL (structural adequacy / integrity / insulation) from AS 1530.4 testing and calculated char method (AS 1720.1 Appendix E / EN 1995-1-2): 3-ply 90mm panel: approximately -/30/30; 3-ply 105mm: -/60/60; 5-ply 140mm: -/60/60; 5-ply 175mm: -/90/90; 7-ply 210mm: -/90/90; 7-ply 245mm: -/120/120. Specific FRL depends on loading ratio, panel configuration, and whether faces are exposed on one or multiple sides. Structural adequacy rating requires residual section verification under design load.
Ignition temp: 250-300 (piloted); 450-500 (auto-ignition) °C Piloted ignition temperature of radiata pine: approximately 250–300°C. Auto-ignition (spontaneous ignition without external flame): approximately 450–500°C. These values inform fire engineering calculations but structural fire design uses the char rate method rather than ignition temperature directly.
Flame spread index: 7-9 (AS 1530.3 Spread of Flame Index) FSI AS 1530.2 early fire hazard indices for radiata pine: Ignitability Index 14–17, Flame Spread Index 7–9, Heat Evolved Index 6–8, Smoke Developed Index 3–5. AS 1530.3 Spread of Flame Index 7–9. NCC Specification C1.10 requires timber to meet Group 3 or better in sprinklered buildings for many applications.
Smoke dev. index: 3-5 SDI Smoke Development Index per AS 1530.2 for radiata pine: approximately 3–5. NCC limits Smoke Developed Index ≤5 for many applications. CLT generally complies with smoke development limits.
Heat release rate: 100-200 (cone calorimeter, 50 kW/m² irradiance) kW/m² Peak heat release rate for exposed CLT in cone calorimeter testing (ISO 5660) at 50 kW/m² irradiance: approximately 100–200 kW/m² for exposed softwood CLT. In compartment fires with exposed CLT, total heat release depends on surface area. Post-flashover CLT contributes to sustained burning; NCC requires encapsulation or sprinklers to limit this contribution in Class 2–9 buildings above 3 storeys.

Cost & Lifecycle

Capex & lead time ·6

Material cost (range): 800-1200 AUD/m³ Indicative supply-only cost from XLam Australia (2024–2025): standard panels approximately AUD 800–1,200/m³ for common thicknesses (100–175 mm). Thinner panels (60–80 mm) or thicker panels (200–280 mm) at premium. Custom widths or complex CNC cutting: additional 10–20%. European import adds approximately AUD 200–400/m³ freight and duty premium.
Material cost (per unit): 80-220 (dependent on thickness) AUD/m² Cost per m² of panel face area at common thicknesses: 100 mm CLT (structural floor) approximately AUD 80–110/m²; 160 mm CLT (heavy floor or wall) approximately AUD 130–165/m²; 200 mm CLT approximately AUD 165–220/m². Excludes CNC cutting, transport, connections, and installation.
Lead time: 6-12 (domestic XLam); 16-24 (European import) weeks XLam Australia (Wodonga, VIC) typical lead time for domestic supply: 6–12 weeks from shop drawing approval to site delivery for standard configurations. Custom panel sizes or large volumes: 10–16 weeks. European import (Stora Enso, Binderholz): 16–24 weeks including shipping. Lead times are capacity-dependent and may vary.
Lifecycle cost: Comparable to concrete over 50-year life when programme savings included AUD/m² Whole-of-life cost advantage of CLT construction includes reduced structure time (20–30% programme saving), lower foundation costs (lighter structure), minimal maintenance for internal CLT, and potential carbon credit value. Quantitative LCC analysis is project-specific; indicative studies suggest CLT is cost-competitive with concrete over 50-year life when programme savings are included.
Annual maintenance: 0.50-1.00 (internal exposed); 5-15 (external) AUD/m²/year Internal exposed CLT (walls, ceilings): negligible maintenance cost — dust cleaning only; estimated AUD 0.50–1.00/m²/year. Internal CLT floor finish: hard wax oil re-coat every 3–5 years at approximately AUD 8–15/m² per treatment = AUD 2–5/m²/year. External CLT: coating maintenance every 2–3 years at AUD 15–30/m² per treatment = AUD 5–15/m²/year.
Market availability: Good (metro eastern seaboard) / Limited (remote Australia) Single domestic manufacturer (XLam Australia, Wodonga VIC) with capacity approximately 30,000–50,000 m³/year. Imports available from New Zealand (XLam NZ), Austria (Stora Enso, Binderholz), and Germany. Market availability is Good in VIC/NSW/QLD metropolitan areas; Limited in remote locations due to transport costs. Growing demand from mass timber pipeline may create supply pressure 2025–2027.

Service life & durability ·3

Expected lifespan: 50-100+ (internal protected); 25-50 (external with H3 + coatings) years Internal CLT protected from moisture and biological attack: 50–100+ years, consistent with traditional timber buildings. External CLT requiring H3 preservative treatment and UV-stabilising coatings: 25–50 years before re-treatment depending on exposure. The BS 7543 / AS 4349.0 service life framework classifies protected internal timber as Durability Class A (>60 years design life).
Maintenance interval: 3-5 (internal floors); 2-3 (external coatings) years Internal exposed CLT: re-coat hard wax oil or penetrating finish every 3–5 years for floor surfaces; wall/ceiling no maintenance required. External CLT: inspect and re-coat UV stabiliser every 2–3 years; re-treat H3 preservative every 10–15 years. External CLT with metal cladding rainscreen: minimal maintenance required on CLT itself.
Warranty period: 10 years XLam Australia provides a structural warranty on panel bond integrity. Typical product warranty is 10 years on manufacturing defects. Structural longevity depends on the level of exposure protection specified by the designer.

Layer D

Where it's used

Structural floor slabs

Load-bearing wall panels

Roof deck and diaphragm

Hybrid CLT-concrete composite floors

External wall cladding substrate

Exposed architectural ceiling and soffit

Stair cores and lift shafts

Acoustic feature panels and baffles

Residential framing (single and two storey)

Prefabricated modular pods

Where it's used

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