Why do fence panels blow down in storms?

Most fence panel failures are caused by inadequate post foundations. A standard 1.83m × 1.83m solid panel experiences forces of 1.5-5 kN in strong winds. Posts set only 300-400mm deep in loose soil cannot resist these forces. Proper 600mm+ embedment in concrete collars of at least 300mm diameter is essential for wind resistance.

What wind pressure should I design my fence for?

In sheltered urban areas, design for 0.5 kN/m². Suburban locations with some shelter should use 0.8 kN/m². Rural exposed sites need 1.1 kN/m², and coastal or hilltop locations should use 1.5 kN/m² or more. These values correspond to wind speeds of approximately 50-95 mph. Always err on the side of caution.

How deep should fence posts be for wind resistance?

For a standard 1.83m fence panel in moderate exposure, posts should be at least 600mm deep in 300mm diameter concrete collars. For exposed sites, increase to 750mm deep with 350mm collars. Very exposed coastal sites may need 900mm+ embedment. The safety factor should be at least 1.5 — meaning the resisting force is 50% greater than the applied force.

Do permeable fences withstand wind better than solid fences?

Yes, significantly. Permeable fences like trellis (30% wind loading) and hit-and-miss (60% wind loading) allow wind to pass through, dramatically reducing the force on posts. A solid close board fence takes 100% of the wind load. In very exposed locations, consider slatted or hit-and-miss designs to reduce wind forces.

What size concrete collar do I need for fence posts?

For standard domestic fencing, a concrete collar of 300mm diameter is typical. For tall fences (over 1.5m) in moderate exposure, use 350mm. Exposed sites should use 400mm or larger collars. The concrete should be C20 mix (1:2:4) and must fully surround the post. Dome the top of the concrete to shed water away from the post.

TradeCalculator

Fence Wind Load Calculator

Calculate wind force on fence panels, required post embedment depth and concrete collar sizing by UK exposure zone.

Panel Height

Standard: 1.83m (6ft)

Panel Width

Standard: 1.83m (6ft)

Fence Type

Permeable types reduce wind loading

Exposure Zone

Location-based wind exposure

Post Size

Post width (75-150mm)

Soil Type

Affects lateral resistance

How We Calculate This

This calculator determines the wind force on fence panels based on exposure zone and panel dimensions, then checks whether the post embedment depth and concrete collar are adequate to resist overturning.

The formula

Total force = Wind pressure × Panel area × Permeability factor
Overturning moment = Force × Height to centre of pressure
Resisting moment = Soil capacity × Collar area × Depth / 2
Safety factor = Resisting moment ÷ Overturning moment (≥ 1.5)

For a 1.83m × 1.83m solid panel in moderate exposure: force = 0.8 × 3.35 = 2.68 kN. Moment = 2.68 × 0.915 = 2.45 kN·m. A 600mm deep, 300mm diameter collar in firm soil provides a safety factor of approximately 1.6.

Storm-proofing tips

Use concrete posts and gravel boards for maximum durability
Concrete collars should be domed to shed water from the post base
Consider hit-and-miss panels in exposed locations
Fence-panel clips or screws prevent panels lifting out of slots

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.