You did everything right. Researched deer fencing specifications. Spent serious money on proper materials. Had it professionally installed or spent weekends doing it yourself to a proper standard. Finally stood back and looked at a fence that should — on paper — keep deer out.
And then you found the damage. Fresh browsing on plants that were supposed to be protected. Tracks inside the fence line. The slow, sinking realisation that somehow, despite everything, deer are still getting in.
It’s one of the most frustrating experiences a gardener or landowner can have. You’ve made the investment, done the work, and it hasn’t solved the problem. Now you’re facing the question of what went wrong and what to do about it.
Why Deer Fences Fail
Deer fencing, when properly designed and maintained, does work. A fence that’s tall enough, strong enough, and complete enough will exclude deer reliably. But the gap between “should work” and “actually works” is where most failures happen.
Understanding the common failure modes helps you diagnose what’s gone wrong — and whether it can be fixed.
Height Miscalculation
The most basic failure is a fence that’s simply too short. And this happens more often than you’d expect, because many people underestimate what deer can do.
Fallow deer — the main problem species around Ashdown Forest and across much of Sussex — are large, athletic animals. A fit fallow buck stands 90cm at the shoulder and can clear a 1.5m fence without breaking stride. Does are smaller but still capable of jumping well over five feet when motivated.
The minimum recommended height for fallow deer is 1.8m, and many professionals recommend 2m to provide a margin of safety. Yet fencing suppliers routinely sell 1.5m or even 1.2m “deer fencing” to customers who don’t know better.
If your fence is under 1.8m and you’re dealing with fallow deer, height is probably your problem. Deer may not jump it every night — they’ll look for easier options first — but when food inside is attractive enough and pressure outside is high enough, they’ll simply go over.
Roe deer are smaller and less athletic than fallow, but they can still clear 1.5m. Muntjac, the smallest species, rarely jump but create different problems that we’ll address below.
Ground-Level Gaps
Deer don’t just go over fences. Many prefer to go under.
Roe deer, in particular, will drop to their knees and crawl under a fence with surprising clearance beneath it. A gap of 15-20cm at ground level — which might not look significant to a human eye — is an open invitation.
Muntjac are even more problematic. These small deer can squeeze through or under gaps that would stop any other species. If you have muntjac pressure and your fence doesn’t extend to ground level, or if there are any points where it’s lifted or undermined, that’s likely your breach.
Ground-level gaps develop over time even in well-installed fences. Soil settles. Animals dig at the base. Water erosion creates channels. Vegetation pushes up from below. A fence that was tight to the ground when installed may have several access points a year later.
Walk your fence line carefully, examining the base at every point. Get down and look from deer height. The gap that’s admitting deer may not be obvious from standing position.
Gate Failures
Gates are the weak point in any fence system. They have to open, which means they have moving parts, hinges that can sag, latches that can fail, and gaps that appear through wear and use.
The most common gate failure is simple: someone left it open. In a household or on a property with multiple users, gates get left unlatched. Deliveries arrive. Children forget. Guests don’t know the routine. One open gate for one night is enough for deer to find their way in — and once they’ve found it, they’ll check it every night thereafter.
Even when closed, gates often have problems. Hinges sag over time, opening gaps at top or bottom. Latches don’t quite catch, allowing gates to swing open in wind. The gate itself may be lower than the adjoining fence, creating a jump point. The base may not meet the ground properly, allowing deer to push underneath.
Gates also represent a psychological weakness: people resist making them difficult to use. A gate that requires wrestling to close properly, or that’s heavy and awkward to manoeuvre, is a gate that gets left open. Good deer gate design balances security against usability.
Mesh Size and Strength
Not all wire mesh is created equal. Cheap fencing uses thinner wire, larger mesh apertures, and weaker construction. It may look adequate when installed but fail under deer pressure.
Deer test fences. They lean against them, push at them, try to force their way through. A large fallow buck can exert considerable force. Mesh that’s too light will stretch, deform, or tear. Staples pull out. Posts shift. What started as a deterrent becomes an inconvenience and eventually an irrelevance.
Muntjac present a specific mesh problem: they can fit through apertures that larger deer cannot. Standard stock fencing with 15cm squares will not stop muntjac. They simply walk through. Effective muntjac exclusion requires graduated mesh with smaller apertures at the bottom, or a separate muntjac-proof layer.
If deer are getting through your fence rather than over or under it, examine the mesh carefully. Look for stretched sections, places where wire has broken or pulled loose, gaps at post attachments. The breach may be obvious or may require careful inspection to find.
Fence Meets Hedge
Fences have to terminate somewhere, and that’s often where they fail.
Where a fence meets a hedge, wall, or other boundary feature, there’s potential for gaps. Hedges are not solid — deer can push through surprisingly dense vegetation if they know there’s food on the other side. Walls may have sections where they’re lower or have collapsed. Other fences may not be deer-proof themselves.
The junction between your fence and whatever it connects to needs to be as secure as the fence itself. If deer can go around the fence by pushing through the hedge at the corner, the fence achieves nothing.
Similarly, any fixed feature inside the fence — a wall, a building, a solid gate — can create a step that deer use to gain height. A fence that’s 1.8m high relative to the ground may only be 1.2m high relative to a raised flower bed or low wall adjacent to it.
Damage Accumulation
Fences degrade over time, and deer remember every weakness they’ve ever found.
Fallen branches land on fences, bending them down or breaking wires. Trees grow against fence lines, creating pressure and potential gaps. Weather loosens posts. Accidental damage from vehicles, garden equipment, or livestock adds up.
Each small degradation may seem insignificant, but deer are checking your perimeter regularly. They notice when the fence is slightly lower in one spot. They test it. They remember. Eventually, accumulated damage creates an access point that wasn’t there when the fence was new.
Maintaining a deer fence requires regular inspection and prompt repair. A fence that’s “mostly intact” is not deer-proof — it’s merely a delay until they find the weakness.
Finding the Breach
If deer are getting inside your fence, you need to find out how. The solution depends on the failure mode, so diagnosis matters.
Track Evidence
Start with the ground. Look for deer tracks — the distinctive cloven hoof prints — in soft soil around the fence perimeter. Concentrate on:
- Along the fence line, where deer walk looking for access
- At gates and corners
- Where the fence meets other boundaries
- Under any low points visible in the fence
Fresh tracks near a specific point on the fence suggest that’s where deer are crossing. Multiple tracks worn into a path indicate an established route they use regularly.
Physical Inspection
Walk the entire fence line, examining:
- Height: Measure at intervals. Fences sag. Posts tilt. What started at 1.8m may be 1.5m in places now.
- Ground gaps: Get down low. Check for daylight under the bottom wire. Look for scraped earth where deer have pushed through.
- Mesh integrity: Look for stretched, broken, or pulled-loose mesh. Check where wires meet posts.
- Gates: Test every gate. Check that they close fully and latches engage. Examine hinges for sagging.
- Junctions: Where the fence meets other boundaries, check for gaps that deer could exploit.
This inspection needs to be thorough. You’re looking for gaps that may not be obvious at a glance. The breach that’s defeating your fence might be a 20cm gap under a sagging section that you’d walk past without noticing.
Trail Cameras
If physical inspection doesn’t reveal the breach, consider deploying trail cameras. These motion-activated cameras capture images of whatever passes, day or night.
Position cameras at likely access points — gates, corners, sections where you’ve seen tracks — and leave them for a few days. Review the footage. You may see exactly where deer are entering and exactly how they’re doing it.
Trail cameras aren’t expensive and can save enormous frustration. Seeing the actual breach is worth far more than guessing at it.
Fixing the Problem
Once you’ve identified how deer are getting in, you can address it — assuming the fix is practical and affordable.
Height Solutions
If deer are jumping your fence, you need more height. Options include:
Adding height to existing fence: Top extensions can increase fence height without complete replacement. These typically involve posts extensions and additional wires or mesh above the current top. This is cheaper than complete replacement but may look awkward and requires careful matching to existing structure.
Complete replacement: For a fence that’s fundamentally too short, replacement with proper height fencing may be the only real solution. This is expensive — essentially you’re paying for fencing twice — but results in a fence that actually works.
Angled extensions: A fence topped with an outward-angled extension is harder to jump than a vertical fence of the same height. The angle makes it difficult for deer to judge the jump and creates uncertainty. This can provide effective additional deterrence without adding massive height.
Ground-Level Solutions
Gaps at the bottom are often easier to fix than height problems.
Buried mesh: The most secure solution is mesh that extends below ground level, buried 30cm or more. This prevents deer pushing under and also deters digging animals. This can be retrofitted to existing fences with some effort.
Ground-level tension wire: A taut wire at ground level, secured tightly with no gap beneath it, prevents deer crawling under. This requires regular checking as the ground shifts over time.
Packed material: For specific gap points, packed earth, gravel, or concrete can eliminate access. This is a quick fix for isolated problem areas rather than a fence-wide solution.
Gate Improvements
Gate problems often have relatively simple solutions:
Self-closing mechanisms: Springs or gravity closers that pull gates shut automatically eliminate the “left open” problem. These require gates hung properly to work.
Better latches: Latches that engage automatically and require deliberate action to open prevent gates swinging open accidentally.
Ground seals: Rubber or brush seals at the base of gates eliminate gaps that deer can push under.
Gate replacement: Sometimes gates are simply inadequate and need replacing with purpose-built deer gates. This is more expensive but solves the problem properly.
When Fixing Isn’t Worth It
Here’s the uncomfortable truth: sometimes the fence you have cannot be made deer-proof at reasonable cost.
If the fence is fundamentally too short, too weak, or too degraded, fixing it may cost more than the fence is worth. Adding 60cm of height to a cheap fence doesn’t give you an expensive fence — it gives you a cheap fence that’s taller. The underlying weaknesses remain.
If your fence has multiple failure modes — too short in some places, gaps at the bottom in others, inadequate mesh, problematic gates — the cumulative cost of fixing everything may approach or exceed the cost of starting fresh.
And even if you do fix everything, you’ve still only addressed exclusion. The deer are still there, still breeding, still increasing. Your fence is a holding action against a pressure that never decreases.
The Alternative: Reduce the Pressure
There’s a different approach to the deer-inside-the-fence problem: instead of making your fence perfect, reduce the number of deer testing it.
A fence doesn’t need to be impregnable if deer pressure is low enough. When there are fewer deer, with adequate food available elsewhere, the motivation to breach your fence diminishes. The gap that a desperate deer would squeeze through, a comfortable deer ignores. The fence that can’t cope with twenty deer visiting nightly handles three occasional visitors just fine.
This is what population management achieves. By reducing deer numbers in your area through humane culling, the pressure on your fence — and your garden — decreases proportionally.
The approach works well in combination with existing fencing. Your fence becomes effective not because you’ve made it perfect, but because you’ve reduced what it has to cope with. Weaknesses that deer were exploiting no longer matter because there aren’t enough deer to find and exploit them.
I provide professional deer management, free of charge, for landowners across Sussex. The exchange is simple: you grant stalking access, I provide sustained population control. Your deer pressure reduces. Your fence — even an imperfect fence — starts working.
This isn’t an either/or choice. The most robust solution combines adequate fencing with population management. The fence provides immediate protection while management reduces long-term pressure. Each makes the other more effective.
Making the Decision
If deer are getting through your fence, you have three options:
Option 1: Fix the fence. Identify the breach, repair it, and maintain more diligently going forward. This works if the breach is specific and fixable, if the rest of the fence is adequate, and if you’re prepared for ongoing maintenance.
Option 2: Replace the fence. Accept that the current fence isn’t fit for purpose and invest in proper deer fencing. This works if you have the budget, if the area is small enough to make fencing economical, and if you’re prepared to maintain the new fence properly.
Option 3: Reduce deer pressure. Accept that fencing alone isn’t solving the problem and address the root cause — too many deer. This works for any property size, costs nothing through my service, and provides lasting benefit beyond just your fence line.
For most landowners, Option 3 — either alone or combined with targeted fencing improvements — provides the most practical and sustainable solution.
I offer free assessments for landowners anywhere in Sussex experiencing deer problems, including those whose fencing hasn’t delivered what they expected. I’ll visit your property, evaluate the situation, and give you honest advice on the best path forward.
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