This under‑sink storage mistake invites mice, warn pest controllers – and the £3 fix from any hardware shop

Emily Turner • December 10, 2025 18:50

The first time you hear it, you blame the washing machine. A soft scritch‑scritch in the quiet bit of the evening, somewhere between the kettle and the back door. You pause, listen, then shrug. Old house, you think. Pipes. Plastic bags settling.

Two weeks later, there are crumbs where crumbs shouldn’t be, a nibble in the corner of the dog food bag, and a neat line of what you desperately hope is coffee grounds along the skirting. You finally do the thing you’ve been avoiding: open the cupboard under the sink and really look.

The smell hits you first – damp wood, old cloths, that faint sour note from the food caddy you keep meaning to empty more often. Behind a tangle of carrier bags and spray bottles, there’s a jagged hole around the pipes and a glimpse of daylight. The pest controller arrives, kneels down, moves one bag, then another, and sighs.

“This,” he says, tapping the gap with a gloved finger, “is a mouse motorway. And you’ve kindly carpeted it for them.”

The mistake is boringly common, he tells you. The fix costs about £3 from any hardware shop. But almost nobody does it until they’ve already got company.

The under‑sink mistake mice are quietly banking on

Most of us treat the under‑sink cupboard as the house’s junk drawer. Half‑used cleaning sprays, spare sponges, carrier bags stuffed into other carrier bags, a dish for mystery keys. If there’s a bin inside, there’s usually a tear in the liner and a streak of something sticky on the base.

Somewhere, hidden behind all that, is the real problem: an unsealed hole where pipes, cables or waste outlets pass through the wall or floor. Instead of properly sealing it, we:

Shove a towel, sponge or old cloth into the gap
Wedge plastic bags or cardboard around the pipes
Simply ignore the daylight showing through, because nothing bad has happened yet

To a mouse, that mess is an invitation. The soft stuff is nesting material. The gap is a front door. The food smells above it are a lure. You could not design a better welcome pack if you tried.

The pest controllers you never wanted to meet have a blunt name for it: an access point. Access beats bait every time. Block that, and most of your mouse problems evaporate before they begin.

Why the cupboard under the sink is rodent central

Once someone points it out, it’s obvious. Under the sink has everything a mouse likes and everything you don’t notice.

Warm pipes and dark corners – a safe, quiet run between rooms
Drips, condensation and leaks – reliable water source, even in winter
Food smells from bins, recycling, compost caddies and pet food
Flexible materials like wood, chipboard and plaster that are easy to gnaw

Mice only need a gap the width of a pencil to squeeze through. That rough notch where the plumber “cut it close” ten years ago? Big enough. The broken bit of foam around the waste pipe? Irresistible.

And when we try to be clever by stuffing fabric or paper into those gaps, we accidentally give them building blocks. They don’t see a draft excluder. They see free bedding.

“If you can fit your little finger in the gap, a mouse will have a go,” one technician told me. “If that gap is hidden behind a bin full of crumbs and carrier bags, they’ve hit the jackpot.”

The £3 fix every pest controller wishes you’d buy

The good news is that the solution is not glamorous, expensive or complicated. It also doesn’t involve filling your house with poison.

What professionals reach for first is usually:

Wire wool (steel wool) or metal scouring pads – around £3 a pack
Sometimes paired with a bit of sealant, filler or tape to keep it in place

Mice can chew wood, plastic, foam and even some softer metals. They do not enjoy gnawing through tightly packed wire fibres. It hurts their gums and wears down their teeth. So they tend to give up and try somewhere else.

That’s why “shove a sponge in it” fails, and “shove wire wool in it” works.

You’ll find it in any hardware shop in the cleaning aisle or near the sandpaper, often sold as:

Steel wool
Wire wool pads
Metal scourers

You do not need a deluxe pest‑control kit or an engineer’s toolkit. You need something scratchy and metallic, a pair of gloves, and ten undisturbed minutes.

How to mouse‑proof your under‑sink in 15 minutes

Before you reach for bait or blockbuster traps, do the cheap, dull job that actually stops the traffic.

1. Strip the cupboard completely

Take everything out. All of it. Yes, even the leaky bleach bottle you’re sure you’ll use “one day”.

Wipe down the base so you can see fresh droppings in future (or, ideally, not see any)
Take the bin bag out, tie it, and leave it outside for now
Put carrier bags somewhere else – they don’t belong here anyway

This is the bit everyone skips. Don’t.

2. Hunt the light (and the gnaw marks)

Turn off the cupboard light if you have one. Use your phone torch and look very slowly around:

The holes where pipes enter the wall or floor
The back corners and under the baseboard
Any cracked sealant, broken plaster or crumbling chipboard

You’re looking for:

Actual holes and gaps
Signs of chewing – rough edges, shredded wood, gnawed plastic
Tracks of droppings along an edge or behind pipes
Smears or rub marks where greasy fur has brushed repeatedly

If you can see daylight around a pipe, that’s a red flag. If you can see outside, that’s basically a welcome mat.

3. Pack gaps with wire wool

Put on gloves – wire fibres are not kind to bare skin.

Pull off a wad of wire wool and push it firmly into the gap around each pipe
Use a blunt tool (like the back of a spoon) to ram it in so it’s tight
For bigger gaps, layer it: stuff, compact, then stuff some more

You want mice to hit a wall of metal, not a token sprinkle.

If you have flexible filler or sealant, you can:

Add a bead over the top to hold the wool in place
Smooth it so it seals draughts as well as vermin

If not, tightly packed wool alone is already a huge upgrade from “bare hole”.

4. Move the food and fix the leaks

Even the best barrier is pointless if the cupboard still smells like a buffet.

Move pet food, bird seed and open packets to sealed tubs or a different cupboard
Don’t keep compost caddies or food bins directly under the sink if you can avoid it
Check for slow leaks or drips and get them fixed – mice love a damp patch

You’re trying to make this space boring. Dry, dull, and not worth the risk.

5. Put fewer things back

This is the part future‑you will thank you for.

Only return:

Essentials you actually use weekly
Items in solid containers (not chewed cardboard boxes)
A small, manageable number of bags or cloths

The more clutter, the more hiding places. A half‑empty cupboard shows problems early. A packed one hides them until you’re googling “what does mouse urine smell like?”.

Tiny habits that quietly invite mice in

Mice are opportunists. It’s rarely one dramatic mistake, more like a handful of small “oh, it’ll be fine” choices that slowly add up.

Common under‑sink habits pest controllers quietly hate:

Letting the bin overflow so the lid can’t shut
Keeping recycling unwashed, especially cans and pet food pouches
Storing chocolate, cereal or snacks in thin cardboard on the floor
Leaving wet cloths, mops or sponges to fester in a corner
Ignoring a faint musty smell because “it’s just damp”

None of these guarantee a problem. They simply tilt the odds in a mouse’s favour. The £3 fix works best when paired with a handful of low‑effort tweaks:

Rinse tins and jars before they go into an indoor bin
Empty food caddies a bit more often than feels strictly necessary
Give the cupboard a 30‑second check when you change the bin liner
Treat any new hole or crack as “fill now, not later”

Think of it as routine maintenance, not a crisis response.

What changes when you do the boring fix first

The day after you pack that ragged hole with wire wool, nothing dramatic happens. No fanfare. No cartoon mouse dragging its suitcase down the street.

What does change is quieter:

The late‑night scritching stops
New droppings fail to appear
Your cleaner doesn’t leave a pointed note
You open the cupboard without bracing yourself

You’ve shifted from chasing symptoms (bait, traps, panic Googling) to fixing the cause (access and attraction). Proof beats poison. If they cannot get in, you do not have to get them out.

Here’s the pattern pest controllers see over and over:

Problem	Usual reaction	Better first move
Droppings under sink	Buy traps and bait	Strip cupboard, seal gaps with wire wool
Chewed pet food bag	Move it 30cm higher	Move it out and into a sealed tub
Occasional scratching	Ignore and hope	Inspect and block access now

The difference is not heroics. It’s timing.

FAQ:

Is wire wool really enough to stop mice?
In most small domestic gaps, tightly packed wire wool is a significant deterrent because it’s painful and awkward to chew. For larger holes, pair it with filler or a metal plate. No method is 100 per cent, but this is the standard first line professionals use.

Can I just use expanding foam instead?
On its own, no. Mice will happily chew through dried foam. If you like foam for draught‑proofing, stuff wire wool into the gap first, then foam over the top. Metal to stop teeth, foam to stop air.

Is poison a bad idea?
Rodenticide has its place, but it carries risks for pets, wildlife and children, and dead mice can end up rotting in inaccessible voids. Most councils and reputable pest controllers now stress proofing and hygiene first, bait only if needed and under guidance.

What if I live in a flat and can’t reach all the pipework?
You can still seal your visible gaps under the sink and around skirting. If you suspect mice are using shared risers or lofts, report it to your landlord or management company – building‑level access points are their responsibility.

How often should I check under the sink?
A quick look whenever you change the bin or buy new cleaning supplies is enough. You’re looking for new holes, droppings, or signs of gnawing. The habit takes seconds and catches problems while they’re still cheap to fix.