Steel gate post size depends primarily on gate weight, gate width, post material, whether the post is braced, and if the gate is automated. Choosing the correct size and type of steel post is critical to ensure gate stability, longevity, and smooth operation.
Steel Gate Post Size Calculator
Here is an in-depth guide covering everything you need to know about steel gate post size:
Key Factors Influencing Steel Gate Post Size
- Gate Weight and Width
Heavier gates and wider gates require larger, stronger posts to support the load and resist sagging or shifting. - Post Material and Wall Thickness
Galvanised steel is common for durability. Wall thickness (measured in millimeters) adds strength to the post. Posts range from 2.5 mm to around 5 mm for heavier gates. - Braced vs. Unbraced Posts
Bracing provides extra structural support. If the post is not braced, a larger and thicker post must be used to compensate. - Gate Type
Swing gates, sliding gates, and bi-folding gates impose different forces on posts, affecting size requirements. - Automation
Automated gates exert significant lateral thrust, requiring reinforced posts and special hinges. - Post Depth and Hole Size for Installation
Correctly sized post holes with concrete bases add stability. The diameter of the hole should be about three times the post width to provide adequate concrete support.
Recommended Steel Gate Post Sizes by Gate Type and Weight
| Gate Type | Gate Width (max) | Gate Weight | Post Size (Square Galvanised Steel) | Wall Thickness | Brace Requirement |
|---|---|---|---|---|---|
| Lightweight Swing Gate | Up to 1 m | Light (aluminium frame, light mesh) | 50 mm x 50 mm aluminum (if braced) or 65 mm x 65 mm galvanized steel (if unbraced) | Aluminium ~3 mm, Steel ≥2.5 mm | If unbraced, larger post size required |
| Medium Weight Swing Gate | Up to 1 m | Medium (aluminium frame with slats or pine palings) | 65 mm x 65 mm aluminum (if braced), 75 mm x 75 mm galvanized steel (if unbraced) | ≥2.5 mm aluminum, ≥3 mm steel | Bracing reduces post size needed |
| Heavy Weight Swing Gate | Up to 1 m | Heavy (steel frame or hardwood) | 75 mm x 75 mm galvanized steel (if braced), 100 mm x 100 mm galvanized steel (if unbraced) | Steel ≥3 mm to 4.8 mm | Critical to brace or increase size for unbraced gates |
| Swing Gates (4 m – 5 m width) | Up to 5 m | Varies by weight | 75 mm to 100 mm square galvanized steel or 125 mm for unbraced/heavy | ≥3 mm steel, 4.8 mm for unbraced | Post size increases with unbraced/unlined gates |
| Bi-folding Gates | Up to 4-5 m width | Varies by weight | 65 mm to 100 mm square galvanized steel braced or 125 mm for unbraced | 2.5-3 mm braced, 4.8 mm unbraced | Similar considerations as swing gates |
| Sliding Gates | Guide posts 1.5-2.2 m high | All weights | 100 mm square galvanized steel with ≥3 mm wall thickness | ≥3 mm steel | Requires sturdier posts due to guide forces |
Source: Experience-based guide from Grants Automation and industry posts
Installation and Hole Size Guidelines for Steel Gate Posts
- The hole diameter should be approximately 3 times the width of the steel post to ensure proper concrete embedment and stability.
- Posts are usually embedded at least 600 mm (24 inches) deep in concrete foundations to resist wind and mechanical forces.
Special Considerations for Automated Gates
- Automation systems exert high lateral thrusts (up to 450 kg+ force on hinges). Posts must be robust enough to resist these forces without damage.
- Use steel posts with thicker walls (≥4 mm) and secure anchoring.
- Employ hinges with tapered thrust bearings or use articulated operators to reduce wear and stress on posts.
Common Steel Sizes in Practice
| Post Size (Square) | Wall Thickness (mm) | Use Case |
|---|---|---|
| 50 mm × 50 mm | 3.0 | Light gates, braced aluminium posts |
| 65 mm × 65 mm | 2.5 – 3.0 | Medium swing or bi-fold gates |
| 75 mm × 75 mm | 3.0 | Heavier gates (swing/bi-fold) |
| 100 mm × 100 mm | 3.0 – 4.8 | Heavy, wide gates, sliding guide posts |
| 125 mm × 125 mm | 4.8 | Very heavy/unbraced posts |
| 150 mm × 150 mm | 5.0 | Double driveway gates |
| 200 mm × 200 mm | 5.0 | Extra heavy or large ornamental gates |
Material and Finish
- Galvanized steel is preferred for corrosion resistance and longevity.
- Options include powder-coated steel finishes for aesthetics and extra protection.
- Steel posts are usually square hollow sections (SHS) for strength and versatility.
Summary
When selecting steel gate post size, consider these three critical variables:
- Gate width and weight: Wider/heavier gates need larger posts with thicker walls.
- Bracing: Braced posts can be smaller; if unbraced, increase size and thickness for strength.
- Installation depth and hole diameter: Embed posts deep enough with properly sized hole and concrete for stability.
For typical residential or equine steel gates, posts commonly range from 65 mm to 100 mm square with 3-4 mm wall thickness. For larger gates, especially automated or heavy-duty applications, posts up to 125-200 mm square with thicker walls are necessary.
Always consult structural or gate specialists if unsure, especially for gates wider than 5 meters or weighing several hundred kilograms, to engineer the correct post specifications.