Straw Bale Construction Units, 450mm thick (450mm)
Structural
ATLAS CODE
ORG-PLA-STR-001
Category organic
Material Family Plant-Based Fibre
Regulatory Status Non-combustible when rendered to AS 1530.1
Density
90-110 kg/m³ (typical construction grade) kg/m³
Carbon (A1-A5)
-0.35 to -0.91 kg CO₂e/kg kgCO₂e
Fire Class
Non-combustible when rendered to AS 1530.1
Lifespan
50-100+ years with maintenance yrs
Description
Straw bale construction units are compressed rectangular bales of cereal straw (wheat, rice, barley) used as structural insulation in walls. Standard Australian bales measure 900mm×450mm×350-400mm, weighing 16-20kg. When rendered with earth, lime or cement-based plasters, they provide exceptional thermal performance, fire resistance up to BAL-FZ, and acoustic insulation. Carbon-negative material when considering sequestration.
Primary Sectors
[Residential][Industrial]
Typical Uses
- Residential external walls (single and double storey)
- Bushfire-resistant construction (all BAL ratings)
- Passive solar design thermal mass walls
- Acoustic insulation walls
- Agricultural and storage buildings
- Community and educational facilities
- Heritage-compatible natural building
- Off-grid and remote area construction
Recycled Content 0% (agricultural by-product)
Renewable Content 100%
Recyclability 100%
Embodied Carbon -0.35 to -0.91 kg CO₂e/kg kgCO₂e
Embodied Energy 0.91 MJ/kg (baling and transport) MJ/kg
EPD Available No
Advantages
Exceptional thermal insulation (R-value 4.8-9)Fire resistant when rendered (FRL 90-90-90)Carbon negative with sequestrationLow embodied energy (<50MJ/m²)Excellent acoustic insulationBreathable wall systemAgricultural waste utilisationSuitable for owner-builder constructionNon-toxic, no VOC emissionsLocally available across grain-growing regions
Cautions
Requires Performance Solution for NCC complianceMoisture sensitive - needs careful detailingLabour-intensive constructionThick walls reduce internal floor areaLimited experienced contractorsRequires protective render systemNot suitable for wet areas without special detailsSettlement requires pre-compressionTransport bulky despite light weightMaintenance of render required
TECHNICAL DATA: PERFORMANCE PROPERTIES ORG-PLA-STR-001
Density (Dry) 90-110 kg/m³ (typical construction grade) kg/m³
Specific Gravity 0.09-0.11
Porosity 85-90% %
Water Absorption <15% moisture content required for construction %
Hardness N/A - compressible material
Surface Roughness N/A - covered by render μm
UV Resistance Poor - requires protective render
Chemical Resistance Moderate - alkaline compatible
pH Tolerance pH 6-9 optimal
Compressive Strength 0.05-0.9 MPa (unrendered), 1.7-6.0 MPa (rendered) MPa
Tensile Strength 0.01-0.02 MPa (perpendicular to straw) MPa
Flexural Strength Dependent on render - typically 0.5-2.0 MPa MPa
Shear Strength 0.02-0.05 MPa MPa
Elastic Modulus 0.05-0.9 MPa (unrendered), 13-19 MPa (rendered) GPa
Yield Strength 10% strain typical yield point MPa
Impact Resistance High - flexible response J/m
Bearing Capacity 40-90 kN/m (rendered wall) kN/m²
Poisson's Ratio 0.1-0.2 (varies with orientation)
Creep Resistance 20-80mm settlement typical under compression
Abrasion Resistance Low - requires protective render
Thermal Conductivity 0.038-0.08 W/m·K (varies with density and orientation) W/mK
Thermal Resistance R4.8-R9 m²·K/W for 450mm thickness m²K/W
Specific Heat Capacity 1600 J/kg·K J/kgK
Thermal Expansion Negligible - accommodated by compression μm/m·K
Melting Point N/A - chars rather than melts °C
Ignition Temperature >300°C °C
Sound Transmission Class (STC) STC 55-60 (rendered wall system)
Noise Reduction Coeff. (NRC) 0.85-0.95 (excellent absorption)
Optical
Light Transmittance 0% (opaque) %
Light Reflectance (LRV) N/A - covered by render %
Solar Reflectance (SRI) Dependent on render finish
Straw bale construction originated in the Great Plains of USA in late 1800s following invention of mechanical balers. Introduced to Australia in 1990s, with first buildings constructed in South Australia and Victoria. CSIRO fire testing in 2002 validated Australian use. Australasian Straw Bale Building Association (AUSBALE) formed to promote standards and training. Over 1000 straw bale buildings now exist across Australia, primarily in grain-growing regions of NSW, Victoria, SA and WA.
SAFETY, ECOLOGY & INSTALLATION ORG-PLA-STR-001
Flame Spread Index 0 (rendered surface)
Smoke Developed Index 0-3 (rendered)
Combustibility Class Non-combustible when rendered to AS 1530.1
Ignition Temperature >300°C °C
Fire Resistance Rating FRL 90/90/90 (rendered) hours
Heat Release Rate Minimal - oxygen-starved environment kW/m²
Toxicity of Combustion Low - natural material
Embodied Carbon (A1-A3) -0.35 to -0.91 kg CO₂e/kg kgCO₂e/kg
Embodied Energy 0.91 MJ/kg (baling and transport) MJ/kg
Water Footprint Variable - dependent on crop irrigation L/kg
EPD Available No
LEED Points Multiple credits possible
Circular Economy Score Excellent - full biodegradability /100
VOC Emissions Zero g/L
Skill Level Moderate - workshop training recommended
Crew Size 4-8 people for wall raising
Installation Time 2-5 days for wall raising (200m² house) hr/m²
Curing Time N/A for bales, 28 days for render hours
Setting Time Immediate placement, compression over 24-48 hours min
Temperature Range 5-40°C installation temperature °C
Humidity Range <70% RH during installation %
Required Tools
Moisture meterChainsaws for notchingCompression equipmentPlastering toolsBale needles for retying
Certifications Required
No specific certification - engineer oversight for Performance Solution
Weather Limitations
Must keep dry during constructionNo installation in rain
COMMERCIAL, LOGISTICS & REGULATORY ORG-PLA-STR-001
Material Cost $3-8 per bale
Installation Cost $1800-4500/m² (complete wall system)
Annual Maintenance $50-200/year (render maintenance)
Lifecycle Cost (50yr) Lower than conventional due to energy savings
Market Availability Seasonal - harvest dependent
Lead Time 2-8 weeks depending on season weeks
Design Life 50-100+ years with maintenance years
Warranty Period Builder-dependent, typically 6-7 years years
Maintenance Interval Annual inspection, 5-10 year render touch-ups months
Service Temp Range -20°C to 60°C °C
Freeze/Thaw Resistance Good with appropriate render system
Dimensional Stability Stable after initial compression
Certifications Held
CSIRO tested (Australian conditions)Suitable for Green Star projectsNABERS energy creditsNo formal certification required - natural material
Fire Code Compliance
AS 3959:2018 (Bushfire)AS 1530.1 (Combustibility - rendered)AS 1530.4 (Fire resistance - FRL testing)
Standards Compliance
NCC Performance Solution requiredNot in DTS provisionsASTM E119 (Fire tests - international equivalent)ISO 834 (Fire resistance)ISO 9869 (Thermal insulation)EN 1365 (Fire resistance tests)
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.