composite / Timber-Based Composite / I-Joist
I-joist, various depths (Specified by depth and flange size)
Engineered LVL-flange/OSB-web I-joists for floor and roof framing with long spans and predictable performance.
Atlas code
COM-TBC-IJT-001
At-a-glance signals
Engineered LVL-flange/OSB-web I-joists for floor and roof framing with long spans and predictable performance.
Overview
Executive summary
I-joists are engineered wood joists with LVL flanges and an OSB web, forming a lightweight I-shaped section. They offer long spans, dimensional stability, and consistent performance for floors and roofs.
Best when…
- Consistent engineered properties
- High strength-to-weight ratio
- Minimal shrinkage and warping
- Long spans without intermediate supports
- Pre-punched service holes available
- Lighter than steel or concrete alternatives
- Sustainable plantation timber source
Top advantages
- 01 Consistent engineered properties
- 02 High strength-to-weight ratio
- 03 Minimal shrinkage and warping
- 04 Long spans without intermediate supports
- 05 Pre-punched service holes available
Top limitations
- 01 Requires weather protection during construction
- 02 Limited fire resistance without protection
- 03 Cannot be notched or cut in flanges
- 04 Requires specific hangers and connectors
- 05 Higher initial cost than solid timber
Technical
Physical ·7
- Density
- 600 kg/m³
- Specific gravity
- 0.6
- Porosity
- 0.35 %
- Water absorption
- 18 %
- UV resistance
- 3
- Chemical resistance
- 3
- pH tolerance
- 5-9
Mechanical ·7
- Tensile strength
- 25 MPa
- Compressive strength
- 8 MPa
- Flexural strength
- 38 MPa
- Shear strength
- 6 MPa
- Poisson's ratio
- 0.35
- Impact resistance
- 3
- Creep resistance
- 4
Sustainability & Health
Embodied carbon & energy ·7
- Embodied carbon
- 280 kgCO2e/m³ Per m³ of I-joist material (engineered wood with adhesive resins).
- Carbon footprint
- 280
- Embodied energy
- 4500 MJ/kg
- Water footprint
- 850 L/kg
- Recycled content
- 0 %
- Renewable content
- 90 %
- Circular score
- 7
Compliance & Fire
Fire performance ·6
- Combustibility class
- Combustible
- Fire resistance level
- 30
- Ignition temp
- 250 °C
- Flame spread index
- 75
- Smoke dev. index
- 150
- Heat release rate
- 150
Cost & Lifecycle
Capex & lead time ·6
- Material cost (range)
- 80-150 // AUD per linear metre
- Material cost (per unit)
- 115
- Lead time
- 1-2 weeks standard sizes
- Lifecycle cost
- 180
- Annual maintenance
- 0
- Market availability
- Readily available
Service life & durability ·3
- Expected lifespan
- 50
- Maintenance interval
- 0
- Warranty period
- 15
Layer D
Where it's used
Residential floor joists
Roof rafters and framing
Commercial floor systems
Cassette floor systems
Rim boards and headers
Wet area set-downs