Why Do I Have Mice? Causes, Risks & What to Do Next
Most mice get in through a gap roughly the width of a pen. They stay because they’ve found food and a warm, hidden place to nest. A female can have a new litter every few weeks, so a few mice can quickly become an infestation.
In London, the usual causes are older buildings, shared walls and voids between flats, and nearby food waste. If you’ve seen a mouse or found droppings this autumn, this guide explains what’s likely causing it, how worried to be and what to do next.
Quick answer:
- How they get in: small gaps around pipes, under doors, in brickwork, or through voids shared with neighbouring properties.
- Why they stay: accessible food, warmth and quiet nesting spots, often behind kitchen units or under floorboards.
- Why now: autumn is when mice move indoors, and activity commonly increases from October.
- Is it serious? Not an emergency, but don’t ignore it. Mice contaminate food and surfaces, gnaw cables and breed fast.
- What to do: secure food, don’t sweep droppings, note what you’ve seen, and get the property assessed so entry points are found, not just the mice.
Why are mice getting into my property?
Mice need three things: a way in, food and shelter. Finding one doesn’t mean your property is dirty. Even a well-kept home or business can have an entry point nobody has noticed.
Small gaps you’d never think to check
Mice squeeze through surprisingly small openings. Common entry points we find in London properties include:
- gaps around pipes and cables where they pass through walls and floors
- worn or missing seals under external doors
- damaged airbricks and brickwork
- gaps behind kitchen units, boxed-in pipework and under baths
- service ducts and risers in flats and commercial buildings
Older buildings are more prone to this, but new builds aren’t immune. Condition matters more than age.
[IMAGE: original photo of a typical entry point, e.g. a gap around a pipe behind a kitchen unit. Alt text: “Gap around a pipe behind a kitchen unit, a common mouse entry point in London homes”]
Hidden routes inside the building
Mice travel through wall cavities, floor voids, ceiling spaces and boxed-in pipework. That means the room where you see them often isn’t where they got in. It’s one reason DIY efforts frequently miss the real problem.
Food, even in small amounts
Crumbs under appliances, open cereal packets, pet food and bins without lids all provide reliable food. In restaurants, cafés and shops, waste storage and cleaning beneath equipment matter most.
Good hygiene reduces attraction, but it won’t stop mice from entering through an open gap. Lasting control means tackling both. The British Pest Control Association’s house mouse guidance explains why food storage, waste management and proofing work together.
Rapid breeding
With food and shelter available, mice breed quickly. Activity that seems occasional can become persistent within weeks, especially when nests are hidden behind units or under floors.
Why am I seeing mice now?
Autumn is when many London properties first notice mice. As temperatures drop and outdoor food becomes scarcer, mice look for warm, sheltered spaces close to food, and homes, restaurants and offices fit the bill.
That said, mice are active all year round. An indoor problem should be investigated whatever the season. For more on the seasonal pattern, see our guides to the autumn rodent surge and mice indoors during winter.
I’ve only seen one mouse. Do I have an infestation?
Possibly. One sighting doesn’t confirm an infestation, but it rarely means there’s only one mouse. Mice are cautious and mostly active at night, so by the time you see one, others are often nearby.
It’s more likely to be an established problem if you’ve also noticed:
- droppings in more than one place, or fresh droppings reappearing after cleaning
- gnawed food packaging, skirting boards or cables
- shredded paper, fabric or insulation that could be nesting material
- scratching in walls, ceilings or under floors, especially at night
- greasy smear marks along walls or skirting boards
- a stale, musty smell in cupboards or under units
If you’re unsure, it’s worth getting advice early. A small problem is quicker and simpler to resolve than one that has had weeks to grow.
Is it a mouse or a rat?
The signs overlap, but a few differences help. A technician will confirm on inspection, as the right treatment depends on which rodent is present.
| Sign | Mice | Rats |
| Droppings | Small, about the size of a grain of rice, pointed ends, scattered | Larger, around 1–2 cm, blunter ends, often grouped |
| Size of animal | Small, with large ears relative to the head | Noticeably larger and heavier, with a blunter nose |
| Where activity shows | Kitchens, cupboards, behind units, inside walls and ceilings | Drains, ground floors, basements, gardens and outbuildings |
| Gnaw marks | Small, fine scratches | Larger, rougher marks |
| Noises | Light scratching and scurrying | Heavier scratching or thudding |
Scratching noises alone can’t confirm which pest you have. Note where and when you hear them so a technician can investigate. If you suspect rats, see our rat control service.
[IMAGE: original side-by-side photo of mouse and rat droppings next to a coin for scale. Alt text: “Mouse droppings compared with rat droppings, with a coin for scale”]
Should I be worried about mice?
Take mice seriously, but there’s no need to panic. They avoid people and prefer to stay hidden. The real concerns are contamination, allergens and damage.
- Food and surface contamination: mice can carry harmful bacteria. Their urine, droppings and movement contaminate food, cupboards and worktops.
- Allergens: proteins in mouse urine and droppings can become airborne and trigger symptoms in some people, including those with asthma.
- Bites: mice may bite if handled or cornered. Never try to catch one by hand. If someone is bitten, follow the NHS advice on animal bites.
- Damage: constant gnawing damages packaging, woodwork and electrical cables. Damaged wiring is a fire risk.
Keep children and pets away from mice, droppings and affected areas.
For food businesses, the stakes are higher. Evidence of mice can affect your food hygiene rating and lead to enforcement action. The Food Standards Agency’s Safer Food, Better Business pack advises contacting a pest contractor immediately if you find signs of an infestation.
Seen signs of mice? Talk to a professional today.
At home: describe what you’ve noticed and we’ll advise on the next steps. Book a consultation or call 020 8050 0238.
Running a business: protect your hygiene rating with discreet, documented treatment. Speak to our commercial team or call 020 8050 0238.
NPTA-accredited · rated 5.0 from 261 Google reviews · serving London since 1997
Why do mice keep coming back in flats and terraced houses?
In many London buildings, your property isn’t a sealed box. Terraces share party walls and roof spaces. Converted Victorian houses and purpose-built blocks share floor voids, risers and service ducts. Mice move freely between them.
That’s why treating one flat on its own often gives only short-term relief. If neighbouring properties or communal areas still have activity, and the routes between them stay open, mice can return.
Lasting results usually depend on:
- finding the routes mice use to reach your property, not just where they appear
- proofing those routes with suitable materials
- where needed, working with neighbours, freeholders or managing agents so shared areas are treated too
Our rodent proofing service focuses on closing these access points. For complex buildings, a rodent proofing consultation can identify where work is needed first.
Can I get rid of mice myself?
Sometimes. If you’ve seen a single mouse, there are no other signs, and you can identify how it got in, simple steps may be enough. For most established problems, though, DIY tends to deal with the mice you can see rather than the reason they’re there.
| DIY | Professional treatment | |
| Best suited to | A single recent sighting with no other signs | Repeat sightings, droppings in several places, or activity that returns |
| Finds entry points | Only the obvious ones | Inspects hidden routes through voids, ducts and shared walls |
| Proofing | Basic gap-filling | Proofing with materials suited to the gap and the building |
| Safety | Risk of misplaced traps or bait near children, pets or food | Methods chosen and positioned around how the property is used |
| Follow-up | Relies on you spotting continued activity | Return visits to check progress and adjust treatment |
| Records | None | Visit reports, useful for landlords and food businesses |
A common pattern: shop-bought traps catch a few mice, things go quiet, and activity returns weeks later because the entry point was never found. If that sounds familiar, it’s time for an inspection.
What should I do right now?
While you wait for advice:
- Secure food. Store it in sealed containers, clear spills, and keep bins closed.
- Don’t sweep or vacuum droppings. This can release contaminated particles into the air. The CDC’s rodent clean-up guidance explains the precautions, or ask us when you get in touch.
- Keep children and pets away from affected areas.
- Don’t disturb nests or try to catch mice by hand.
What to note before you contact us
The more you can tell us, the more accurately we can advise. If you can do so safely, note:
- Sightings: how many mice, and on which dates? Repeated sightings may be the same mouse.
- Locations: which rooms or areas? Has activity stayed in one place or spread?
- Timing: day, night or particular times?
- Other evidence: droppings, gnawed packaging, gnaw marks or possible nesting material.
- Possible entry points: visible gaps under doors, around pipes or in damaged fittings.
- Your property: house, flat, conversion or commercial premises, and whether neighbours have mentioned mice.
You don’t need to inspect behind units or disturb anything. Photos help: you can upload them through our contact form or send them on WhatsApp.
How does Obsidian deal with mice?
Our mice removal and control service starts by understanding the problem and the property, then builds treatment around what we find.
- Initial consultation. You speak to a trained member of our team about what you’ve noticed. Depending on the information and photos you share, we may be able to outline a likely treatment plan at this stage.
- Inspection. A technician assesses evidence of activity, likely entry routes, nesting areas and anything that may be supporting the infestation, such as accessible food or waste.
- Clear recommendations and quotation. We explain what we found, the treatment we recommend, any proofing work and the expected follow-up. You’ll know exactly what’s involved before you agree to anything.
- Treatment tailored to your premises. Depending on the findings, this may include monitoring, trapping, appropriate baiting and proofing. Our trained, qualified and insured technicians select and position products and equipment around children, pets, food preparation areas and how the space is used.
- Follow-up and prevention. Return visits check progress, look for continued or renewed activity and adjust treatment where needed. We also explain practical steps to stop mice coming back.
“Darren is always professional, friendly, reliable, and thorough when checking our shop for any signs of mice.” – Google review
How much does mouse pest control cost?
Every job is quoted individually, because no two infestations are the same. The cost depends on what’s actually happening in your property, so we prefer to understand the problem before giving a price rather than quote a figure that later changes.
The main factors are:
- The extent of activity: a recent, contained problem needs less work than an established one.
- The size and type of property: a studio flat, a terraced house and a restaurant kitchen need different approaches.
- Proofing: whether entry points need sealing, and how many.
- Number of visits: how much follow-up is needed to confirm the problem is resolved.
- Access and shared areas: whether voids, risers or neighbouring spaces are involved.
- Ongoing protection: whether a business needs a regular pest management contract.
For full transparency, we review the extent of the problem first. Any callout fee is clearly disclosed upfront, after an initial phone consultation. The more information and photos you can share at that stage, the clearer the picture we can give you of the likely treatment plan.
A quote that’s too good to be true often skips the inspection or the proofing, which is usually why mice come back.
How long does it take to get rid of mice?
It depends on the size of the problem and how quickly entry points can be closed. A contained problem may resolve over a few visits. An established infestation, or one involving shared spaces, takes longer.
What we can promise is clarity. After the inspection, we’ll explain the expected number of visits and what each one is for, so you know what to expect from the start.
I rent my home. Is my landlord responsible for mice?
Often, but it depends on the cause and your tenancy agreement. As a general guide:
- Landlords are usually responsible where mice get in because of disrepair, such as damaged brickwork, gaps or faulty fittings, or where the property wasn’t free of pests when the tenancy began.
- Tenants may be responsible where the problem is linked to how the property is used, such as food left out or rubbish not disposed of properly.
- Flats: shared areas and the building structure are usually the responsibility of the freeholder or managing agent.
- Landlords and managing agents: we work across London’s rental and block-managed properties, with clear visit reports for your records. Talk to us about your property.
Mice in a restaurant, café, shop or office
For food businesses, mice are a compliance issue as well as a hygiene one. UK food law requires businesses to have adequate procedures to control pests, and evidence of mice during an environmental health inspection can lower your food hygiene rating. In serious cases, it can lead to enforcement action or temporary closure.
What environmental health officers typically expect to see:
- an active pest control arrangement with a professional contractor
- records of visits, findings and actions taken
- evidence that recommendations, such as proofing or hygiene improvements, have been carried out
- clean, well-managed waste storage and food areas
One-off callouts deal with a problem once it appears. A regular pest management contract helps prevent it, with routine inspections, monitoring and the documentation you need to show due diligence.
We support restaurants, hotels, offices, managing agents and retail premises across London, with discreet visits planned around your trading hours. Read more in our guide to pest control for businesses.
Protect your premises and your rating. Request a commercial consultation or call 020 8050 0238.
Frequently asked questions
Does having mice mean my home is dirty?
No. Mice can get into clean, well-kept properties through small gaps. Hygiene affects whether they stay, but access is usually the root cause.
Will mice go away on their own?
Rarely. If they’ve found food and shelter, they tend to stay and breed. Activity may seem to drop, then return.
Are your treatments safe around children and pets?
Our trained technicians choose and position treatments around how your property is used, including children, pets and food areas. We’ll explain any precautions you need to follow.
Can you tell me the cost before visiting?
Every job is quoted individually. After an initial phone consultation, we’ll explain any callout fee upfront. With enough detail and photos, we may be able to outline a likely treatment plan before the inspection.
Do you cover my area?
We’re based in Soho and cover Central and Greater London, including North, South, East and West London.
Can you help if another company’s treatment didn’t work?
Yes. Repeat problems are often caused by entry points that were never found or proofed. We’ll inspect from scratch.
Speak to Obsidian about mice in your property
Whether you’ve seen a mouse, found droppings or heard scratching in the walls, we’ll help you understand what’s happening and what to do next.
| Homeowners and tenants | Businesses, landlords and managing agents |
| Tell us what you’ve noticed and send photos. We’ll advise on next steps and arrange an inspection where needed. | Discreet, documented treatment and ongoing contracts that support environmental health compliance. |
| Book a home consultation | Request a commercial consultation |
Call 020 8050 0238 · email info@obsidianpestcontrol.co.uk · or message us on WhatsApp.
NPTA-accredited · Trained, qualified and insured technicians · 65+ years of combined experience · Serving London since 1997 · rated 5.0-star on Google
