How to Stop Rats From Getting Under Your Decking
Updated: Aug 18
A practical guide for UK homeowners on rat prevention, the right exclusion mesh, and smart decking design.
Discovering rats under your decking is one of those problems that catches homeowners completely off guard. One day you're enjoying your garden, the next you're hearing scratching beneath your feet and spotting signs of burrowing along the deck edges.
At Duralive Decking, we're asked about this more often than you might expect — particularly from homeowners across Merseyside and Cheshire who are either planning new composite decking or upgrading an existing timber deck. And the question is almost always the same:
"How do I stop rats from nesting under my decking — and what's the right way to do it?"
The answer involves three things: removing what draws rats in, installing the right physical barrier, and making the space under your deck less appealing long-term. This guide walks you through all of it, so you can either do it properly yourself or know exactly what to specify if you'd rather have it done.
Just want the checklist? We've condensed this whole guide into a two-page Deck Rodent-Proofing Checklist — mesh spec, burial depths, ventilation clearances and the sequence to follow. Free to download, no site visit required.
Why Rats Get Under Your Decking — and How to Stop Them
Understanding what brings rats to your decking is the most important starting point, because prevention only works if you're addressing the right causes.
Decking itself doesn't "attract" rats the way food does. But the sheltered void beneath a deck is exactly what rats look for: cover, warmth, concealment, and a safe place to move between locations. If food and water are also nearby, a deck can quickly become a regular stopping point — and eventually, a nesting site.
In gardens across the UK, the most common accidental "rat feeders" are spilled bird seed beneath hanging feeders, pet food left outside overnight, overflowing bins or compost heaps close to the deck, and warm compost bins full of food scraps.
Norway rats — the most common species in UK gardens — are particularly fond of concealed burrows. Typical burrow entrances are just a few inches across, and burrows often sit under 18 inches deep, with multiple entry and exit points. Along deck edges, foundations, and beneath debris are their preferred spots.
The key principle: your deck is the cover. Remove the food, the water, and the harbourage, and you've already made the problem much less likely.
Removing What Draws Rats In: Food, Water and Cover
Before you install any physical barrier, address the environmental factors that make your garden attractive in the first place. The most durable solutions combine proofing (exclusion) with hygiene and harbourage removal — the approach recommended by UK pest control guidance as a longer-term alternative to relying on rodenticides.
Practical steps to reduce rat attraction:
Move bird feeders well away from the decking. Fallen seed is one of the most consistent "invisible feeders" in UK gardens. Switch to no-mess mixes and use a tray beneath feeders to catch spills.
Don't leave pet food outside overnight. Even a single bowl is enough to establish regular rat activity in the area.
Secure bins and compost heaps. Use lidded bins, and consider protecting compost heaps with wire mesh if they're close to the deck.
Clear debris and vegetation around the deck perimeter. Overgrown areas, wood piles and dense planting give rats the cover they need to move around undetected.
Remove wood piles, bricks or garden waste stored beneath or near the deck. These are common nesting materials and should be relocated away from the structure.
One thing to skip: ultrasonic and electromagnetic "repellers" are widely available but are not recommended as reliable solutions by credible pest control guidance. Physical exclusion combined with hygiene measures is the method that consistently holds up over time.
⚠ Critical warning: don't seal animals in
Multiple rodent-proofing sources are clear on this point: do not seal access points until you know what's using them and have a control plan in place.
Sealing active burrows or gaps while rats are present can increase damage inside the void, prompt additional gnawing attempts, and make the problem significantly harder to resolve. If there are signs of active infestation — fresh droppings, soil disturbance, gnawing damage — deal with the rats first, then install the exclusion barrier. We cover the correct sequence further down.
The Right Exclusion Mesh: Size, Material and Gauge
What mesh size do you need?
The Timber Decking and Cladding Association (TDCA) specifically recommends welded mesh with a 5 mm hole pattern installed around the deck edge to prevent rat access. Public health guidance commonly cites 1/4 inch (approximately 6 mm) as the benchmark for excluding both rats and mice.
Some sources use 1/2 inch (12–13 mm) for rats alone — but in practice, gardens often have both species, and homeowners frequently confuse the two. UK pest guidance also notes that rats may only need a gap of around 15 mm to get into a structure, which is much tighter than most people expect.
Our recommendation: use 5 mm or 1/4-inch (6 mm) welded mesh. It's effective against both rats and mice, aligns with TDCA guidance, and leaves no ambiguity about coverage.
Wire type, gauge and corrosion resistance
Hole size is only part of the equation. In a garden environment — particularly in the wet conditions common across Merseyside and Cheshire — the wire itself also needs to last.
Welded at each joint, not twisted. Welded mesh holds its shape under pressure and doesn't unravel if a single strand is damaged.
Galvanised after welding for the best corrosion resistance. Wire wool, by contrast, corrodes surprisingly quickly in damp conditions and is only a short-term measure.
16–19 gauge wire. Widely recommended for demanding exclusion applications. It costs more upfront but resists gnawing and lasts significantly longer.
Avoid aluminium or plastic screening. These are temporary deterrents only — rats will defeat them over time, particularly where they can find a rough surface or exposed edge to gnaw.
How to Install Mesh That Actually Works
The most common failure point in decking exclusion isn't the mesh itself — it's how it's installed. Rats don't typically push through mesh directly. They dig under it, or find gaps where the mesh meets the frame or the ground.
There are two well-supported installation methods that consistently appear across credible pest exclusion and construction guidance.
Method 1: The vertical skirt with buried depth
The TDCA recommends fitting mesh 300 mm vertically (around 12 inches) into the ground around the deck edge where it meets the ground. This depth is consistent with exclusion barrier guidance from other pest control and construction sources and provides sufficient resistance against burrowing. The top of the mesh must be secured tightly to the deck frame to eliminate any gap at the junction between mesh and structure.
Method 2: The L-shaped buried apron
A particularly effective alternative — especially where digging a deep trench all the way around is impractical — is the L-shaped curtain barrier.
Fix the mesh vertically against the deck frame, extending it down to ground level. At the base, bend the mesh outward horizontally by approximately 150 mm (6 inches). Stake the horizontal section flat and cover it with soil or gravel.
The buried apron stops rats digging under the base of the vertical section. The extra effort required to get past the buried shelf means this approach often achieves strong anti-dig performance without needing an extremely deep trench the whole way around.
Rats under your deck right now?
If the deck is already built, retrofitting exclusion properly means lifting boards or fascia, trenching the perimeter, checking the subframe for gnawing and rot, and reinstating airflow — and the sequence matters, or you'll be doing it twice.
Deck Rodent-Proofing Survey — £95, redeemable in full against any work booked. We come out, inspect the void and subframe, identify how they're getting in, and give you a fixed written price. Typical retrofit installs run £1,200–£3,500 depending on deck perimeter and access.
Covering Merseyside, Cheshire, Liverpool, Warrington, St Helens, Widnes and Wirral. Call 0151 808 5102.
Keeping Airflow While Keeping Rats Out
When homeowners skirt a deck tightly to exclude rodents, there's a real risk of accidentally reducing airflow and creating a moisture problem beneath the boards — particularly damaging for composite decking. In the damp climate of Merseyside and Cheshire, this needs designing out from the start, not fixing after the fact.
How much clearance do you actually need?
150mm between the soil and the underside of the frame is what we recommend. It's the clearance that lets air move properly, keeps the frame well clear of ground moisture, and makes the void possible to inspect and clean.
However, that isn't always achievable. Where a low-level deck is required — 50mm is acceptable, provided the ventilation is designed properly and the ground beneath is drained and membraned.
Below 50mm, we recommend changing the subframe material. At that height air movement is minimal and the frame will spend part of the year in damp conditions, so a timber subframe is on borrowed time. We'd specify a recycled plastic or aluminium subframe instead. They're impervious to rot, unaffected by standing moisture, and don't offer rats anything soft to gnaw. It costs more upfront, but it's the right call when the levels leave you no other option.
Clearance alone isn't ventilation
Any open edge will let air in. What separates a deck that stays dry from one that doesn't is where that air gets out.
Air under a deck warms, picks up ground moisture and rises; with nowhere to escape it sits against the underside of your boards and rots them.
So you need two openings, not one:
Intake — low and open along the exposed edges, drawing cool air in across the gravel.
Exhaust — high and unobstructed. On a deck against the house, air rises out along the wall. Butt the deck hard to the brickwork and you've capped it. An inlet with no outlet = no movement.
Freestanding decks work the same way — vent at least two opposite sides, so one draws in and one lets out. Underneath it all: weed-control membrane topped with gravel or chippings for drainage. Check out our blog on Composite Decking Ventilation: Why Airflow Under Your Deck Matters to find out more about ventilating decking properly.
Why mesh is the right skirt material
This is where exclusion and ventilation stop competing. Welded mesh is the only skirt that gives you open vent area and a physical barrier in the same plane — air circulates freely through the apertures while rats face something they can't defeat.
A solid skirt may keep rats out, but also traps moisture in. It's the most common mistake we see on DIY and low-cost retrofits. You solve one problem and buy yourself a bigger one three winters later.
Design Features That Help Long-Term
Build in an inspection hatch
One of the most useful and most frequently overlooked design features is a liftable board or access hatch positioned to allow inspection of the under-deck void. TDCA guidance specifically recommends this, particularly near manholes or drain covers where rats are more likely to be active.
By the time most homeowners hear rats beneath their deck, the problem is already well established. Building in easy access from day one — without lifting random boards and risking damage to fixings — is a low-cost design decision with an outsized practical benefit.
Keep the space under the deck unattractive
Physical exclusion works best when the void is also made as unappealing as possible for nesting:
Lay weed-control fabric topped with gravel or chippings. This reduces available nesting material and makes the sub-deck area much less hospitable.
Maintain a vegetation-free perimeter. Clear grass and ground cover back from the deck edge to create an open zone that makes rat movement exposed.
Remove leaf litter and debris periodically. A dark, debris-filled void is far more attractive than a clean, open, well-drained one.
What If Rats Are Already Present?
If you suspect rats are already nesting under your decking, the sequence matters.
Do not seal access points. Closing gaps with active rats inside creates a more complex and damaging problem.
Contact a qualified pest controller. A professional can identify the species, assess the scale of activity, locate burrow entrances and put a targeted control plan in place.
Then install exclusion properly. Once the infestation has been dealt with, fit the barrier correctly and make the environmental changes described in this guide to prevent reinfestation.
Trying to shortcut this by simply blocking holes is one of the most common mistakes homeowners make — and one of the most likely reasons rat problems reappear.
We work alongside local pest control firms across Merseyside and Cheshire. They clear the infestation; we fix the structural reason it happened in the first place. If you're not sure who to call first, get in touch and we'll point you in the right direction.
How Composite Decking Reduces the Risk
There is one area where the choice of material makes a genuine practical difference: the sub-deck structure.
Traditional timber subframes can splinter, rot, and provide easy footholds for gnawing — over time they can even become a source of nesting material in themselves. Aluminium or composite subframe systems, increasingly standard with premium composite decking installations, offer significantly less natural harbourage and are far more resistant to gnawing damage.
At Duralive Decking, we regularly install composite decking systems from Millboard, Trex and NewTechWood across Merseyside, Cheshire, Liverpool, Warrington, St Helens, Widnes, Wirral, Wigan, Ormskirk and Formby. Our design approach always considers the sub-deck environment — ground clearances, drainage, and where required, integration of rat exclusion mesh as part of the build specification. If you're weighing up budget, our composite decking cost guide sets out what a properly specified deck actually costs.
If you're planning new composite decking, this is the ideal time to address rat prevention properly: before the boards go down, not after.
Final Thoughts
Rats under decking is a solvable problem — but only if the solution is properly specified and correctly installed. The right mesh, the right depth, the right installation method, and a deck design that supports long-term ventilation. Get those four things right and you'll have a structure that's genuinely inhospitable to rodents for the lifetime of the deck.
Sort it properly, once
Already have rats, or want to make sure you never do? Our Deck Rodent-Proofing Survey is £95, and redeemable in full against any work booked. We inspect the under-deck void and subframe, identify the entry points, check for gnawing and rot damage, and give you a fixed written price.
What we can install: correct 6 mm galvanised welded mesh to the right depth, with a buried apron where the ground demands it; airflow retained to manufacturer clearances, so no trapped moisture and no voided warranty; the sub-deck void cleaned, membraned and gravelled so it stays inhospitable; and an inspection hatch fitted so you can check it yourself in future.
Typical retrofit installs run £1,200–£3,500 depending on deck perimeter and access. If the subframe is too far gone to be worth saving, we'll tell you straight and price a rebuild instead.
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