Panel · 60–280 mm
Timber-Based Composite — indicative fig. C·44
Fire Combustible CombustibleEmbodied carbon -0.98kgCO₂e/kg Stores carbonCompressive 25 (parallel to grain) / 5.5 (perpendicular to grain)MPa StructuralDesign life 50yr
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.
01 Physical
Density 500kg/m3
Specific gravity 0.5
Porosity 40-50%
Water absorption Hygroscopic — equilibrates to ambient RH% by weight
Hardness 2200Janka
UV resistance Low (uncoated) / Good (with UV-stabilising coating)
Chemical resistance Moderate — resistant to dilute acids, susceptible to strong alkalis and concentrated mineral acids
pH tolerance 4.5-5.5pH
Surface roughness 1-15μm Ra
02 Mechanical
Tensile strength 16 (parallel to grain, F8 characteristic)MPa
Compressive strength 25 (parallel to grain) / 5.5 (perpendicular to grain)MPa
Flexural strength 30 (F8 characteristic, major axis)MPa
Shear strength In-plane: 3.5-5.0; Rolling shear: 1.0-1.5MPa
Poisson's ratio 0.43-0.51
Impact resistance Impact sound Ln,w ~75-80 dB bare; 48-55 dB with floating floor systemJ/m²
Creep resistance Moderate — creep is a design consideration for long-span CLT floors; kdef = 0.8 (SC1)
03 Thermal
Thermal conductivity 0.12W/mK
Specific heat 1600J/kgK
Thermal expansion 4-5×10⁻⁶/K
04 Compliance & Fire First question
Combustibility class Combustible (AS 1530.1) / EN 13501-1: D-s2,d0
Fire resistance level 30/30/30 to 120/120/120 depending on thickness and loadingminutes
Ignition temp 250-300 (piloted); 450-500 (auto-ignition)°C
Flame spread index 7-9 (AS 1530.3 Spread of Flame Index)FSI
Smoke dev. index 3-5SDI
Heat release rate 100-200 (cone calorimeter, 50 kW/m² irradiance)kW/m²
05 Sustainability & Health
Embodied carbon -492kg CO2-eq/m3
Carbon footprint -0.98 (including biogenic) / +0.12-0.16 (fossil only)kg CO2-eq/kg
Embodied energy 700-900 (fossil, non-renewable primary energy)MJ/m3
Water footprint 200-500L/m³
Recyclability 70-85%
Recycled content 0%
Renewable content 98-99%
Circular score 7/10
VOC emissions <10 (formaldehyde); <100 (total VOC)μg/m³
Toxicity rating Low (finished product) — wood dust hazard during cutting requires PPE
LEED contribution Up to 4-5 (LEED v4 across multiple credits)points
06 Durability · Cost · Logistics
Expected lifespan 50-100+ (internal protected); 25-50 (external with H3 + coatings)years
Maintenance interval 3-5 (internal floors); 2-3 (external coatings)years
Warranty period 10years
Material cost (range) 800-1200AUD/m³
Material cost (per unit) 80-220 (dependent on thickness)AUD/m²
Lead time 6-12 (domestic XLam); 16-24 (European import)weeks
Lifecycle cost Comparable to concrete over 50-year life when programme savings includedAUD/m²
Annual maintenance 0.50-1.00 (internal exposed); 5-15 (external)AUD/m²/year
Market availability Good (metro eastern seaboard) / Limited (remote Australia)
07 Assessment
Advantages
- 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
Constraints
- Combustible — requires careful fire engineering and may need encapsulation
- Moisture sensitive — panels must be protected on site during construction
- Higher material cost than concrete slab or steel deck equivalents
- Limited domestic manufacturing capacity creates potential supply constraints
- Acoustic flanking paths through rigid CLT connections require careful detailing
- Proprietary connection systems add design complexity
- Requires structural engineer experienced in timber design (AS 1720.1)
- Perceived fire risk can create insurance or occupier concerns
- Formaldehyde from adhesives requires MDI/PUR specification and ventilation
- End-of-life reuse is logistically challenging despite theoretical recyclability
08 Applications
A1 Structural floor slabs CLT panels used as primary floor structure in mass timber buildings, residential apartments, commercial offices, and education buildings up to 8 storeys (NCC DTS pathway). Typically 100–175 mm thick, spanning 4–8 m between supports.
A2 Load-bearing wall panels Structural wall panels for gravity and lateral load resistance, including shear walls in mass timber cores. 80–140 mm typical for residential; 100–160 mm for commercial buildings.
A3 Roof deck and diaphragm CLT roof panels spanning between primary framing members, acting as a structural diaphragm to transfer lateral loads to shear walls. 80–120 mm typical for roof applications.
A4 Hybrid CLT-concrete composite floors CLT used as permanent formwork with shear connectors and concrete topping, providing composite structural action for longer spans and improved acoustic performance.
A5 External wall cladding substrate CLT structural wall panel with insulation, breather membrane, and external cladding overlay. H3-treated CLT required where panels may be exposed to incidental moisture.
A6 Exposed architectural ceiling and soffit CLT floor panel exposed on the underside as a finished ceiling surface. Biophilic aesthetic benefit; natural grain and warm tones. Requires architectural-grade face specification and protective finish.
A7 Stair cores and lift shafts CLT panels forming structural cores for stairs and lifts in mass timber buildings, providing robust, dimensionally stable enclosures. Typically encapsulated with plasterboard for NCC fire compliance.
A8 Acoustic feature panels and baffles Perforated or grooved CLT panels used for acoustic absorption in educational, cultural, and office interiors. NRC 0.20–0.40 with appropriate perforation pattern.
A9 Residential framing (single and two storey) CLT as an alternative to light timber framing for premium residential projects. Provides higher thermal mass, better acoustic separation, and structural simplicity for open-plan layouts.
A10 Prefabricated modular pods CLT panels used as structural substrate for prefabricated bathroom, kitchen, or service pods assembled off-site and craned into position. Offers programme and quality advantages for hotel and residential projects.
09 Sources & Standards
References
- XLam CLT Panel Product Data Sheet (V4, September 2023) · manufacturer
- XLam Structural Design Guide Australia & New Zealand (June 2020) · manufacturer
- XLam CLT Panel Product Technical Statement Australia (September 2023) · manufacturer
- Environmental Product Declaration — XLam CLT Panel (EPD-IES-0002326, S-P-02326) · database
- WoodSolutions Technical Design Guide 16 — Massive Timber Construction Systems / CLT · industry
- WoodSolutions Technical Design Guide 50 — Mid-rise Timber Building Structural Engineering · industry
- AS 1720.1-2010 (incl. Amdt 1, 2, 3) — Timber structures, Part 1: Design methods · standard
- ABCB Australian Fire Engineering Guidelines (AFEG) 2021 · government
- FPInnovations Canadian CLT Handbook (2019 Edition) · industry
- Comparative Evaluation of Fire Performance Predictions for Glulam and CLT Under International Design Standards (J. Compos. Sci., 2026) · research
- Review of the charring rates of different timber species (Liu, Fire and Materials, 2024) · research