Know Your Posts
Complete guide to selecting the right galvanised steel posts for your signage installation.
Understanding Post Specifications
Choosing the correct post is critical for safety, compliance, and longevity. This guide helps you understand Nominal Bore (NB) sizes, duty classifications, and Australian Standards requirements.
Post Nominal Bore (NB) Sizes
NB refers to the nominal bore (internal diameter) of the pipe. The outer diameter (OD) determines the actual size.
50NB
60.3mm OD- Use: Light traffic control signs, parking signs, small regulatory signs
- Typical Signs: Stop signs, Give Way signs, speed limit signs, parking signs
- Max Sign Area: Up to 0.6-0.9 m²
- Common Heights: 2.1m - 3.6m posts
65NB
76.1mm OD- Use: Medium-sized regulatory and warning signs
- Typical Signs: Larger warning signs, directional signs in low-speed areas
- Max Sign Area: Up to 1.2 m²
- Common Heights: Primarily 6.5m for taller installations
80NB
88.9mm OD- Use: Larger warning signs, guide signs, multi-sign assemblies
- Typical Signs: Overhead guide signs, larger warning signs on highways
- Max Sign Area: Up to 2.0 m²
- Applications: Higher wind load areas, larger sign panels
90NB
101.6mm OD- Use: Large directional signs, highway signage
- Typical Signs: Freeway guide signs, large directional assemblies
- Max Sign Area: Up to 3.0 m²
- Applications: High-speed roads, exposed locations
100NB
114.3mm OD- Use: Very large signs, multi-panel assemblies
- Typical Signs: Large overhead guide signs, major highway signage
- Max Sign Area: 3.0+ m²
- Applications: Freeways, major arterial roads
125NB & 150NB
139.7mm & 165.1mm OD- Use: Extra-large sign structures, gantries, overhead signage
- Typical Signs: Freeway overhead structures, large VMS (Variable Message Signs)
- Max Sign Area: 5.0+ m²
- Applications: Major highways, freeway gantries, large multi-sign structures
Duty Classifications
Duty classification refers to wall thickness and structural capacity. Select based on application requirements and expected loads.
Extra Light Duty
1.6mm - 2.0mm wall✓ Suitable For:
- Low-speed areas (< 60 km/h)
- Urban streets with minimal wind exposure
- Light-weight signs (< 0.5 m²)
- Private roads, car parks, residential areas
✗ NOT Suitable For:
- High-speed roads
- Exposed areas
- Public highways
Light Duty
2.0mm - 2.6mm wall✓ Suitable For:
- Urban roads (60-80 km/h)
- Suburban areas with moderate exposure
- Standard regulatory signs
- Light to medium sign loads (0.5 - 1.2 m²)
- Most urban signage applications
✗ NOT Suitable For:
- High-speed highways
- Very large signs
- Extreme wind zones
Medium Duty
2.6mm - 3.2mm wall✓ Suitable For:
- High-speed roads (80-110 km/h)
- Exposed coastal/wind-prone areas
- Larger signs (1.2 - 2.5 m²)
- Multi-sign assemblies
- Public highways and main roads
- Most public road applications
- Long-term installations
Australian Standards: AS1163 vs AS1074
AS1163
Preferred StandardPurpose
Structural applications requiring high strength and certified capacity
Characteristics
- Higher manufacturing tolerances
- Certified structural capacity
- Consistent wall thickness
- Suitable for load-bearing applications
When Required
- Public roads and highways (VicRoads/Main Roads requirements)
- Large or heavy signs (> 1.5 m²)
- High wind load zones (AS/NZS 1170.2)
- Multi-sign assemblies
- Cantilever or overhead structures
- Where engineer certification is required
Typical Use
80% of public road signage in Australia
AS1074
Economy OptionPurpose
General mechanical and structural applications
Characteristics
- Lower manufacturing tolerances
- Not certified for structural calculations
- May have variable wall thickness
- Adequate for non-critical applications
When Acceptable
- Private property (car parks, warehouses)
- Low-speed areas (< 60 km/h)
- Small signs (< 0.6 m²)
- Non-public roads
- Temporary signage
Limitations
- NOT acceptable for most public road authorities
- May not meet RMS/VicRoads/TMR specifications
- Cannot be used where engineer certification required
Typical Use
Private developments, internal roads, car parks
State-Specific Requirements
VicRoads (Victoria)
- AS1163 mandatory for all VicRoads-managed roads
- AS1074 may be accepted for < 60 km/h local roads with approval
- Minimum 50NB Medium Duty for regulatory signs
NSW RMS/TfNSW
- AS1163 required for classified roads
- AS1074 acceptable for council roads < 60 km/h
- Engineer certification required for signs > 1.2 m²
Queensland TMR
- AS1163 mandatory for state-controlled roads
- Cyclone-rated posts (AS1170.2 Region C/D) in northern areas
Practical Selection Guide
| Application | Speed | Sign Area | Recommended Post | Standard | Duty |
|---|---|---|---|---|---|
| Car park signs | < 40 km/h | < 0.5 m² | 50NB x 2.1m | AS1074 | Extra Light |
| Urban residential | 50-60 km/h | 0.5-0.9 m² | 50NB x 2.8m | AS1074/AS1163 | Light |
| Suburban main road | 60-80 km/h | 0.6-1.2 m² | 50-65NB x 3.6m | AS1163 | Light/Medium |
| Highway (100 km/h) | 100-110 km/h | 1.0-2.0 m² | 80-90NB x 4.4-6.5m | AS1163 | Medium |
| Freeway overhead | 110 km/h | 2.0-5.0 m² | 100-150NB x 6.5m | AS1163 | Medium/Heavy |
| Coastal exposed | Any | Any | +1 size up | AS1163 | Medium minimum |
Key Takeaways
AS1163 is the "safe choice" for public roads - most authorities require it
AS1074 saves cost but only suitable for private property or council-approved low-speed areas
Extra Light Duty = car parks and private roads only
Light Duty = urban streets and residential areas
Medium Duty = main roads, highways, and anywhere public safety is critical
Bigger NB size = larger signs, higher wind loads, more structural capacity
Always check local authority requirements before specifying - they override general guidelines
Need Help Selecting the Right Post?
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