Question 1

What frame section should I use for a steel gate?

Accepted Answer

For pedestrian gates (up to 1m wide), 40x40x3 RHS is adequate. For single vehicle gates (up to 3m), 50x50x3 or 60x40x3 RHS is standard. For double gates (3-6m total) or tall gates (over 2m), 80x40x3 or heavier sections are needed. The frame must resist self-weight deflection (sag) and wind loading without excessive flex.

Question 2

How deep should gate posts be set in the ground?

Accepted Answer

There is no code-mandated figure for steel gate post embedment, so the common trade rule of thumb is roughly one-third of the total post length below ground, with a practical minimum of about 600mm for pedestrian gates and 900-1200mm for vehicle gates. The post is set in a concrete foundation (C20/25 minimum, often C25/30 for heavy gates) — around 300mm square for pedestrian and 450mm square for vehicle gates. These are conventions, not regulated values; for tall, heavy, exposed or automated gates the post and foundation should be designed by a structural engineer to resist the actual overturning moment.

Question 3

How do I size hinges for a steel gate?

Accepted Answer

There is no British Standard for domestic steel-gate hinge selection, so these are fabricator rules of thumb — always confirm against the hinge manufacturer's published load table. As a guide, sized by per-leaf weight: under 50kg uses a 16mm pin / 150mm strap; 50-100kg a 20mm pin / 200mm strap; 100-200kg a 25mm pin / 250mm strap (ball bearing); over 200kg a 30mm pin / 300mm ball-bearing strap. Use 3 hinges for leaves over 100kg or over 2m tall. For heavy or automated gates have the hardware confirmed by a structural engineer.

Question 4

What do I need for an automated gate?

Accepted Answer

This calculator does not size gate automation — it covers the gate weight, frame, hinges, posts and foundation only. For motorisation you would typically need: (1) a gate motor matched to leaf weight and length (ram or articulated-arm actuator for swing gates, rack and pinion for sliding gates); (2) safety devices to limit closing force, plus photocells and safety edges — the safety-in-use standard in the UK is BS EN 12453 (with BS EN 12604 for mechanical aspects and BS EN 12978 for safety devices); BS EN 13241 is the product/CPR standard; (3) an adequate power supply (230V or 24V with battery backup); (4) a manual release for power failure. In Great Britain powered gates are placed on the market under the Supply of Machinery (Safety) Regulations 2008 (UKCA). Note HSE issued a formal objection to BS EN 12453/13241 after powered-gate fatalities, so compliance with the standard alone is not sufficient — a full risk assessment is required, and the DHF codes of practice (TS 011 swing/sliding, TS 013 traffic barriers) are widely followed.

Question 5

What finish should I use for external steel gates?

Accepted Answer

For UK external use, hot-dip galvanising (to BS EN ISO 1461) is essential for long-term durability. This can be left as-is (grey) or overcoated with powder coating for a colour finish (duplex system — 25+ year life). Alternatively, galvanise and apply two-pack polyurethane paint. Never paint raw steel without galvanising for external gates.

Steel Gate Calculator — Frame, Hinges & Post Sizing

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