Why Your Fence Fails Below Ground: 7 Groundwork Mistakes to Avoid Before Winter (and How to Fix Them)

When it comes to a fence that stays upright through winter, the work you cannot see is often the most important. I have seen firsthand how a smart-looking panel can fail because the post beneath it was set into shallow, wet or poorly prepared ground.

That matters even more before winter. Waterlogged soil can offer less reliable support, frost can lift shallow footings, and wind puts extra strain on posts and panels. If you are planning work now, here are seven groundwork mistakes to look out for, and what you can do to avoid them.

1. Setting posts too shallow for the ground and load

Symptom: Posts lean or rock, particularly after strong winds. Gates may also begin to sag or catch.

Cause: The footing does not provide enough support for the fence’s height, weight, exposure or soil. A tall, solid panel catches more wind than a low, open design; a gate puts additional forces on its hinge posts.

Fix: Set depth and footing size according to the site, post and fence system, not just a one-size-fits-all rule. Around 600 mm is often used as a starting point for ordinary garden fencing, but it is not a universal specification. Exposed sites, soft ground, taller fences and gate posts may need a different detail or a professional assessment.

I recommend asking your installer to explain the proposed depth and how it suits your soil and fence design. A clear specification now can help prevent movement later.

2. Leaving out a proper concrete collar or haunching

Symptom: A post becomes loose at ground level, even when the concrete around it looks substantial.

Cause: Concrete may not fully surround and support the post. Voids, loose backfill or a poorly shaped footing can let the post move. At the same time, a flat concrete finish can collect rainwater against timber.

Fix: The footing should be properly formed around the post, with the post held straight while the concrete sets. Finish the top so water drains away rather than sitting against the timber. For timber posts, use products suitable for their intended ground contact and treat cut ends as directed by the supplier.

Remember: adding concrete alone is not a cure-all. The footing must suit the ground and shed water effectively.

3. Ignoring drainage at the post line

Symptom: Water sits around post bases, the ground becomes soft, or timber starts to deteriorate near ground level.

Cause: Rainwater or runoff collects along the fence, leaving the soil saturated. A stone layer at the bottom of a hole will not solve the problem if the water has nowhere to drain.

Fix: Look at the whole site before digging. Check slopes, downpipes and places where surface water naturally gathers. Address the source of runoff where possible, and choose a footing detail suitable for the soil. If a post hole continually fills with water, stop and reassess rather than pouring concrete into a flooded excavation.

For timber, I recommend checking the specified ground-contact treatment and keeping water from pooling at the base. Forest Garden’s fencing guidance also offers practical advice on post installation and keeping water away from timber.

4. Installing in wet, frozen or waterlogged ground

Symptom: Fresh footings shift, posts move before the concrete sets, or holes collapse as work progresses.

Cause: Saturated soil can be unstable and difficult to compact. Frozen ground may thaw and move, while freezing temperatures can affect the early curing of concrete. If posts are set into unsuitable conditions, the finished fence may not hold its line.

Fix: Work during a suitable spell when excavations are stable and the concrete can be placed and protected in line with product instructions. If the ground is frozen, holes are collapsing or water keeps entering, postpone the work or use a site-specific alternative. Do not rush to finish a fence simply to beat the weather.

Winter weather also increases the risk of frost heave: water in susceptible soil freezes and expands, potentially lifting a shallow footing. After thawing, voids can remain around it. A well-planned installation considers local soil and drainage rather than relying on extra concrete as a quick fix.

5. Reusing old post holes or building over failed footings

Symptom: A replacement post becomes loose soon after installation, or a new fence follows the same leaning line as the old one.

Cause: An old hole or footing may be cracked, too shallow, badly positioned or surrounded by disturbed soil. Putting a new post into it can repeat the original failure instead of fixing it.

Fix: Inspect and assess each old footing before deciding whether it can be reused. Remove failed concrete and loose material where needed, then make sure the new post is founded in suitable ground. Check the position and depth against the new fence layout, especially if the replacement panels are taller or more solid than the old ones.

If you are replacing only part of a boundary, check neighbouring posts too. One sound-looking section may still be affected by movement elsewhere.

6. Skipping the site survey and peg-out

Symptom: The fence line wanders, panels do not meet cleanly at corners, or the finished height changes unexpectedly across the boundary.

Cause: Without a site survey and a clear peg-out, installers may miss changes in level, obstacles, access constraints or the exact boundary line. Posts set to the wrong spacing can also leave awkward gaps or require improvised cuts.

Fix: Before digging, walk the proposed route and agree the line, levels, corners, gates and changes in height. Mark it with pegs and a string line so you can see where the fence will sit. Check for buried services and confirm any boundary or access details before work begins.

A careful set-out is especially useful on sloping ground or where the fence meets a building, wall or existing gate. It gives you an opportunity to spot problems before they become permanent.

7. Splitting groundworks and fencing between contractors

Symptom: Posts move or footings fail, but it is unclear who is responsible for putting things right.

Cause: If one contractor prepares the holes and another installs the fence, important details can fall between the two scopes: post depth, hole condition, concrete finish, drainage and the time allowed for curing.

Fix: Agree in writing who is responsible for the full sequence, from survey and excavation through to setting the posts and installing the panels. If different contractors are involved, make sure the specification, handover and checks are clear. Take photos of the groundworks before they are covered.

This accountability matters for domestic fencing and is particularly important for commercial sites. For high-security perimeter fencing, foundation details are part of the security installation, not a separate afterthought. Infrastructure security specialists should coordinate the specification and installation so the system is appropriate to site conditions and the project has clear ownership.

Why planning before winter is worth it

Winter does not automatically rule out fencing work, but it can narrow the window for reliable groundworks. Waterlogged soil may lose stability; frozen ground can make excavation and curing difficult; and wind loading on saturated posts can expose weak footings. If the conditions are unsuitable, waiting for a workable spell is safer than installing in a rush.

For homeowners considering luxury garden fencing London, the foundations deserve the same attention as the finish. When FSC-certified timber is specified for posts or panels, confirm the product is suitable for its intended use and follow the supplier’s installation guidance.

Be cautious of a very low quote that does not explain the materials, guarantee or groundwork. Inferior materials can shorten a fence’s useful life; an absent guarantee leaves you with less clarity if workmanship fails; and no detailed written quote makes it hard to know what has actually been included. Ask for the scope, materials, post details and exclusions in writing.

At Fenceways, our 10-year guarantee covers workmanship and fixings. Third-party components are covered on the manufacturer’s own terms. Failures caused by groundwork completed by others fall outside our guarantee, which is why agreeing responsibility before work starts matters.

A practical checklist before you book

1. Ask for a site survey and a marked-out fence line.

2. Confirm how post depth and footing size suit your soil, fence and exposure.

3. Discuss drainage and what happens if holes fill with water.

4. Agree who is responsible for all groundworks and installation.

5. Request a detailed written quote and check the guarantee and exclusions.

I always recommend consulting with fencing professionals where the ground is saturated, the fence is tall or exposed, or the project involves gates or security requirements. You can explore our fencing and gate services or contact Fenceways to arrange a site visit. Better groundwork now gives your fence a stronger start before winter weather arrives.