MATERIAL DATA SHEET

Spotted Gum timber cladding/screening, various grades & profiles (19mm, 21mm, 25mm, 32mm)

Structural Timber
organic › Timber › Structural Timber
organictimberstructural-timberspotted-gumhardwoodeucalyptuscladdingscreeningaustralian-nativeBAL-29durability-class-1bushfire-compliantcarbon-sequesteringsustainable-forestry
ATLAS CODE
ORG-TBR-ST-001
Spotted Gum timber cladding/screening, various grades & profiles (19mm, 21mm, 25mm, 32mm)
Category organic
Material Family Timber
Regulatory Status Combustible — Group 3 (AS 5637.1), BAL-29 compliant (AS 3959)
Density
950 kg/m3
Carbon (A1-A5)
150-350 (gross); net negative including sequestration kg CO2-eq/m3
Fire Class
Combustible — Group 3 (AS 5637.1), BAL-29 compliant (AS 3959)
Lifespan
50-80+ years
Description

Spotted Gum (Corymbia maculata) is Australia's premier structural hardwood for cladding and screening, combining exceptional mechanical strength with natural durability. This eucalyptus species achieves Durability Class 1 above ground (40+ years, AS 5604), Strength Group SD2 with stress grades to F34 when seasoned, and BAL-29 bushfire compliance without additional treatment at 18mm+ thickness. Density of approximately 950 kg/m3 at 12% moisture content delivers a Janka hardness of 11.0 kN, superior fixing retention, and excellent impact resistance. The distinctive wavy interlocked grain produces prized fiddleback figuring, with heartwood colours ranging from light brown to dark chocolate. Available in cladding profiles (shiplap, tongue-and-groove, weatherboard) and screening battens (42x19mm to 90x42mm) from sustainably managed native forests across eastern Australia.

Primary Sectors
[Commercial][Institutional]
Typical Uses
  • External wall cladding (horizontal shiplap/weatherboard)
  • Privacy screening (vertical batten systems)
  • Pergola and outdoor structure cladding
  • Bushfire-prone area construction (BAL-12.5 to BAL-29)
  • Commercial and institutional facades
  • Interior feature walls and ceiling linings
  • Fencing and boundary screening
  • Coastal construction applications
8314mm
Size
Primary Form [83x14mm / To / 140x32mm / Cladding; / 42x19mm / To / 90x42mm / Screening]
Dimensional Tol. ± [+/- 0.5mm thickness, +/- 1.0mm width] mm
Recycled Content 0 (new); up to 100 (reclaimed)
Renewable Content 100
Recyclability 95
Embodied Carbon 150-350 (gross); net negative including sequestration kg CO2-eq/m3
Embodied Energy 500-1500 MJ/m3
EPD Available No
Advantages
Exceptional structural strength — Strength Group SD2, stress grades F17-F34 (seasoned, AS 2082)Durability Class 1 above ground (40+ years service life per AS 5604)BAL-29 bushfire compliance without treatment at 18mm+ thickness (AS 3959 Appendix F)Janka hardness 11.0 kN — superior impact and abrasion resistanceNatural termite resistance (heartwood)100% Australian grown and processed from sustainably managed native forestsDistinctive wavy grain with prized fiddleback figuringExcellent weathering characteristics — silvers gracefully when left unfinishedCarbon-sequestering material — stores approximately 850 kg CO2/m3Long service life 50-80+ years with minimal maintenance
Cautions
Premium pricing ($115-300+ AUD/m2 depending on profile and grade)High density (950 kg/m3) mandates pre-drilling for all fixingsNatural colour variation from light brown to dark chocolate requires sorting for consistent facadesInterlocked wavy grain causes machining difficulties and potential tearing during planingSapwood susceptible to lyctid borer attack — must be excluded from exposed applicationsHigh density causes accelerated tool wear — tungsten-carbide blades requiredSeasonal movement requires 3-5mm expansion gaps and proper ventilation detailingHeavy material increases handling difficulty and transport costs
CLAD MATERIALS ATLAS PAGE 1 OF 4
TECHNICAL DATA: PERFORMANCE PROPERTIES ORG-TBR-ST-001
Density (Dry) 950 kg/m3
Specific Gravity 0.95
Porosity 8-12 %
Water Absorption 10-14 %
Hardness 11.0 kN
UV Resistance Moderate
Chemical Resistance Good
pH Tolerance 4-8 pH
Available Colors
Natural heartwood: light brown to pale gold (freshly sawn)Natural heartwood: mid brown to warm chocolate (common range)Natural heartwood: dark brown to deep chocolate (dense growth)Weathered/silvered: pale grey to silver-grey (12+ months unfinished exposure)Oiled: enhanced warm brown tones depending on oil type (natural, tung, Danish)Stained: can accept penetrating stains for custom colours (semi-transparent or solid)
Surface Finishes
Natural/unfinished — weathers to silver-grey over 6-12 monthsPenetrating oil (Cutek, Intergrain, Sikkens) — enhances grain, 12-24 month recoatFilm-forming stain (semi-transparent) — UV protection with grain visibility, 3-5 year recoatSolid body stain — opaque colour over grain, 5-7 year recoatPre-finished factory coating — Mortlock/supplier applied, better consistency and warrantyClear sealant — UV-protective clear with limited colour change prevention
Texture Options
Dressed/planed smooth (DAR — dressed all round)Rough-sawn — rustic industrial aestheticBrushed/textured — wire-brushed to accentuate grainSand-blasted — aged appearance with raised grain textureNatural fiddleback figuring — premium boards selected for wavy grain pattern
Pattern Options
Horizontal shiplap — traditional weatherboard profile with shadow lineTongue-and-groove — flush face or V-joint profilesVertical board-and-batten — country/contemporary aestheticVertical screening battens — 42x19mm to 90x42mm with variable spacingDiagonal cladding — feature applications at 30-45 degreesHit-and-miss screening — alternating front/back battens for privacy with airflow
Compressive Strength 55-70 MPa
Tensile Strength 100-130 MPa
Flexural Strength 142 MPa
Elastic Modulus 19.8 GPa
Impact Resistance 80-110 J/m
Creep Resistance Excellent
Abrasion Resistance Excellent
Thermal Conductivity 0.19-0.21 W/mK
Thermal Resistance 0.09-0.17 m2K/W
Specific Heat Capacity 1400-1600 J/kgK
Thermal Expansion 0.003-0.005 mm/mK
Ignition Temperature 300-350 degC
Sound Transmission Class (STC) 25-28 STC
Noise Reduction Coeff. (NRC) 0.05-0.10 NRC
Optical
Light Transmittance 0 %
Light Reflectance (LRV) 25-40 %
Electrical
Electrical Conductivity Insulator (dry) S/m

Spotted Gum (Corymbia maculata, reclassified from Eucalyptus maculata in 1995) has been valued as one of Australia's premier structural timbers since early colonial settlement. The species was extensively used in heavy engineering applications — bridge construction, wharf piling, railway sleepers, and mining timbers — where its exceptional strength-to-weight ratio and natural durability proved invaluable. The common name derives from the distinctive mottled bark pattern left as the bark sheds in patches. Indigenous Australians used the straight-grained timber for spear shafts, digging sticks, and boomerangs. Modern sustainable forest management across NSW and Queensland state forests maintains commercial supply, with plantation trials also established. The timber gained renewed architectural prominence from the 1990s onward as designers rediscovered its structural and aesthetic qualities for contemporary facades, screening, and landscape structures. Its listing in AS 3959 Appendix F for BAL-29 bushfire construction has further increased demand in bushfire-prone regions across southeastern Australia.

CLAD MATERIALS ATLAS PAGE 2 OF 4
SAFETY, ECOLOGY & INSTALLATION ORG-TBR-ST-001
Flame Spread Index 100-150 FSI
Smoke Developed Index 150-250 SDI
Combustibility Class Combustible — Group 3 (AS 5637.1), BAL-29 compliant (AS 3959)
Ignition Temperature 300-350 degC
Fire Resistance Rating 30-60 minutes
Heat Release Rate 150-250 kW/m2
Toxicity of Combustion Low
Embodied Carbon (A1-A3) 150-350 (gross); net negative including sequestration kg CO2-eq/m3
Embodied Energy 500-1500 MJ/m3
Water Footprint 5-20 L/kg
EPD Available No
Recycled Content 100%
Renewable Content 100%
LEED Points 6-9 points
Circular Economy Score 9 /10
VOC Emissions <E1 (very low) ug/m3
Skill Level Experienced (hardwood carpentry)
Crew Size 2-4 people
Installation Time 3-6 hours/10m2
Curing Time 0 hours
Temperature Range 5-40 degC
Humidity Range 30-75 % RH
Required Tools
Heavy-duty circular saw with tungsten-carbide-tipped (TCT) blade — standard steel blades dull rapidlyPre-drilling equipment — MANDATORY for all fixings (drill + countersink combination bits)High-torque impact driver with stainless steel or Class 4 galvanised screwsDrop saw / mitre saw with TCT blade for crosscuttingBelt sander or orbital sander for end-grain finishingMoisture meter (pin-type) for MC verification before installationSpirit level, string lines, and laser level for alignmentAppropriate PPE — dust mask (hardwood dust is a respiratory irritant), hearing protection, eye protection
Certifications Required
Licensed builder or qualified carpenter (Australian state licensing requirements)Working at heights certification (for facade installations above 2m)Construction White Card (general construction induction)Knowledge of AS 1684 (Residential Timber-Framed Construction) for structural applicationsFamiliarity with AS 3959 (Construction of buildings in bushfire-prone areas) for BAL zone work
Weather Limitations
Do not install during rain — timber must remain below 15% MCProtect delivered timber from direct rain and ground moisture with bearers and coveringAllow timber to acclimatise to site conditions for 48-72 hours before installationAvoid finish application in direct sun, high humidity (>85% RH), or temperatures below 10 degCInstall ventilated cavity (min 20mm air gap) behind cladding for moisture management
CLAD MATERIALS ATLAS PAGE 3 OF 4
COMMERCIAL, LOGISTICS & REGULATORY ORG-TBR-ST-001
Material Cost 95-300+ AUD/m2
Installation Cost 35-70 AUD/m2
Annual Maintenance 0.50-8 AUD/m2/year
Lifecycle Cost (50yr) 180-400 AUD/m2
Market Availability Good
Lead Time 5-28 days
Supply & Logistics
Design Life 50-80+ years
Warranty Period 15-25 years
Maintenance Interval 1-5 years
Service Temp Range -10 to 65 degC
Dimensional Stability 0.3-0.4 per 1% MC % change
Certifications Held
AS 2082 — Timber — Hardwood — Visually stress-graded for structural purposesAS 2796 — Timber — Hardwood — Sawn and milled products (appearance grading)AS 1604 — Specification for preservative treatment (when sapwood treatment required)AFS (Australian Forestry Standard) / PEFC certified — sustainably managed native forestsFSC certification available from select suppliersResponsible Wood certification (Australian program endorsed by PEFC)VOC emissions below E1 (World Health Organisation levels)No formaldehyde emissions (natural untreated timber)GECA (Good Environmental Choice Australia) eligible
Fire Code Compliance
AS 3959:2018 — Construction of buildings in bushfire-prone areas (BAL-12.5, BAL-19, BAL-29 compliant at 18mm+ thickness)AS 5637.1 — Determination of fire hazard properties — Group 3 materialNCC 2022 Volume 1 Section C — Fire resistance (with appropriate assembly details)AS 1720.4 — Timber structures Part 4: Fire resistance of structural timber members
Standards Compliance
NCC 2022 (National Construction Code) — compliant for structural and non-structural applicationsAS 1684 — Residential timber-framed construction (span tables and design)AS 1720.1 — Timber structures Part 1: Design methodsAS 1720.2 — Timber structures Part 2: Timber propertiesAS 5604 — Timber — Natural durability ratings (Class 1 above ground, Class 2 in-ground)ASTM D143 — Standard test methods for small clear specimens of timberASTM E84 — Surface burning characteristics of building materialsISO 13061 — Physical and mechanical properties of woodISO 3129 — Wood — Sampling and general requirements for physical and mechanical testingEN 350 — Durability of wood and wood-based products (Class 1 equivalent)EN 338 — Structural timber strength classes (D50-D60 equivalent)

DISCLAIMER: This specification document is generated from the CLAD Materials Atlas Database. Information is for general guidance only and does not constitute professional engineering advice. Values are typical and may vary by batch, manufacturer, and production run. Verify suitability for specific project applications independently.

ID: ORG-TBR-ST-001 Schema: v3.0
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