Fence Leaning After High Winds

What's happening?

A close-boarded or panel fence is a solid barrier, so wind cannot pass through it: it pushes against the whole face and that load ends up entirely on the posts and their foundations. When a fence leans after a gale, the panels have usually done their job and the post fixings have not. What has moved is nearly always at or below ground level: a post rotated in soft ground, a concrete collar that was too small or too shallow, a post set in soil rather than concrete, or the timber failing right at the ground line. The lean tells you which. A whole run tipping together points to undersized foundations across the fence; one post out of line points to that single fixing. And a lean rarely stays put: the ground around a moving post opens up, so each subsequent gale moves it further.

What usually causes it?

• Posts set too shallow for the fence height, so there is not enough embedded depth to resist the overturning force
• Concrete collars too small, or posts bedded in soil, hardcore or dry mix rather than concrete
• Timber posts rotted at the ground line, so the post has failed where the load is highest
• Waterlogged or soft ground around the posts, allowing them to rotate under wind load
• Solid panels or added trellis increasing the wind load beyond what the original posts were installed for
• Ivy, climbers or a heavy hedge on the fence, adding weight and turning it into a bigger sail
• Rails or fixings failing so the fence loses its stiffness and racks over as a whole

Is it dangerous?

Treat a leaning fence as unstable until it is fixed. A panel fence has a large area and real weight, and the next gust that takes it down can hit a person, a car, a shed or a greenhouse, and the risk is highest on the side where children play or where the fence borders a pavement or a shared path. Two things push it up the urgency list: a fence leaning towards a public footpath, road or a neighbour's property, and a fence carrying any electrical cable, light or gate motor. Do not prop it and consider it dealt with.

Can I fix it myself?

Work out where the movement is before spending anything. Grip each post and push: the one that moves at ground level is the failed fixing. Then push a screwdriver into the post at the ground line: if the blade sinks in easily, the timber has rotted and no amount of re-concreting the same post will help. Photograph the lean against a plumb line so you can tell whether it worsens. Cutting ivy and climbers off the fence reduces the load immediately and is worth doing straight away. Temporary bracing back to a stake keeps it upright while a repair is arranged; it is not a repair.

When should you call a fencing and gate installer?

Call a fencing installer promptly, and sooner if the fence borders a pavement, road, shared path or a neighbour's garden, or if it carries wiring, a light or a gate. If several posts have moved, the fence is at the end of its life rather than in need of a patch, and it is worth having the whole run assessed in one visit rather than one post at a time. Get it looked at before the next spell of bad weather, not after it.

What will the fencing and gate installer actually do?

• Test each post individually, probing the timber at ground level to separate a rotted post from a moved foundation
• Excavate the failed post holes and assess the ground conditions and existing concrete
• Reset or replace posts to an embedded depth suited to the fence height, in properly mixed and sized concrete collars
• Replace rotted posts rather than re-concreting them, or fit a concrete or steel post to a sound panel run
• Realign the run to a string line and re-fix rails, panels and gravel boards square
• Reduce the wind load where it has been increased (removing added trellis, cutting climbers off the fence), and advise where post spacing or type should change

Who fixes this

• Fence repair after a storm
• Fence post replacement

Questions people ask

Sources & References

1. Planning Portal: Fences, gates and garden walls
2. BS 1722-5, Fences: specification for close boarded fences
3. Wood Protection Association