Finding out you have mice in your walls can be unsettling. The good news is that this is a common issue and there are safe, effective steps you can take to resolve it. In this guide, we’ll explain how to spot the signs of mice living in your walls, practical DIY methods to remove them, and how to prevent future infestations. Acting quickly is important to protect your home and health. Let’s get started.
Signs of Mice Living in Your Walls
Knowing the signs of a mouse infestation is the first step. Mice are mostly active at night and often hide within wall cavities, so you might not see them straight away. Look for these common indicators:
- Scratching and scurrying noises: If you hear light scratching, gnawing, or scampering sounds coming from within walls or ceilings (especially at night), it’s a strong sign of mice. They often make noise as they climb, chew and move around in wall voids.
- Droppings: Mice leave behind small dark droppings about the size of a grain of rice. You might find these droppings under kitchen units, in cupboards, along skirting boards, or near suspected entry points. Fresh droppings are soft and moist, while older ones are dry. Seeing even one is a warning of mouse activity.
- Gnaw marks and holes: Check for gnawed wood, chewed plastic, or cardboard. Mice chew constantly to wear down their teeth. You may notice bite marks on skirting boards, wiring (which is a fire hazard), or holes chewed in food packaging like cereal boxes. Small holes in walls, floors, or cabinets with frayed edges could mean mice have created an entrance.
- Unusual ammonia-like smell: A strong, musky odour can develop from mouse urine, especially in enclosed spaces like wall cavities or lofts. If you notice a persistent foul smell (similar to ammonia or stale urine) in certain areas, it could be due to a build-up of mouse urine and droppings. The stronger the smell, the closer you may be to their nest or activity.
- Grease marks: As mice run along walls, their bodies can leave oily rub marks on surfaces. Look for dark smudges on walls or skirting boards, especially near holes or runways the mice might use as they travel from the wall to food sources.
- Nests or shredded materials: Mice build nests using whatever soft materials they find. If you come across shredded paper, torn insulation, fabric scraps, or stuffing gathered in hidden corners (lofts, airing cupboards, behind appliances), this could be a mouse nest. Nests are often hidden in wall cavities or under floorboards, so you might only find them if you investigate these areas.
- Pet behaviour: Sometimes dogs or cats will show unusual interest in a particular wall or cupboard, scratching or sniffing persistently. This can be a hint that they hear or smell rodents inside.
If you notice one or more of these signs, it’s likely you have mice taking shelter in your walls and/or somewhere else. Once you’re aware of their presence, it’s important to take action promptly.
DIY Steps to Get Rid of Mice in Walls
Tackling a mouse problem early can prevent a small issue from becoming a big infestation. Here are some practical DIY steps you can follow to help get rid of mice in your walls:
Seal Entry Points
Mice can squeeze through incredibly small gaps – even openings as small as the width of a pencil. Inspect your home or business thoroughly, inside and out, for any holes or cracks that might be letting mice in.
Common entry points include gaps around plumbing pipes, cables entering walls, vents, damaged air bricks, and cracks in the exterior brickwork or foundation. Seal any holes you find to block their access. Use sturdy materials that mice cannot chew through: for example, pack steel wool or wire mesh into holes and then apply caulk or filler over it. Pay extra attention to gaps under doors (fit brush or rubber door sweeps to eliminate gaps) and around window frames. By proofing your home like this, you not only stop more mice from entering but also help confine the ones already inside so you can deal with them.
Remove Food Sources
One of the main reasons mice moved in is likely the availability of food. Removing these attractants will make your home much less appealing.
Start in the kitchen: store all food in sturdy airtight containers (plastic or glass with tight lids) instead of open boxes or bags. This includes dry goods like cereals, rice, pasta, and pet food.
Clean up any spilled foods or crumbs from cupboards, worktops, and floors – even tiny crumbs can feed a mouse. Ensure cleaning happens straight away so crumbs don’t linger.
Take the rubbish out regularly and use bins with tight-fitting lids. If you have a compost or outdoor bins, ensure they are well sealed to avoid attracting rodents.
Don’t forget pet food: avoid leaving pet bowls with food out overnight. By depriving mice of easy meals, you’ll encourage them to take bait from traps and make your home less hospitable for them.
Use Traps Effectively
Traps are one of the most effective DIY methods to catch and kill mice in walls. Snap traps (break-back traps) are widely recommended because they kill mice quickly.
The mice will come out of the wall to feed so this is your opportunity to catch them.
Place traps near areas of high activity – along walls behind appliances, in cupboards, or near the suspected wall entry holes. Mice tend to run along edges, so set the traps perpendicular to the wall (with the trigger end against the wall) so they can be sprung from either direction. Bait the traps with foods that mice love. Peanut butter is an excellent bait (its strong smell attracts mice and it’s sticky, making them work the trap), but you can also use chocolate, or other high-calorie foods. We recommend Snickers bar as the best bait.
Always wear gloves when handling traps and bait to avoid leaving your scent and to protect yourself from germs. Check traps at least once a day and dispose of any caught mice promptly.
Safety note: If you have children or pets, place traps in areas they cannot reach (for example, inside a box with small mouse-sized holes or behind heavy furniture). This prevents accidental injury from the trap.
Mouse Poisons
You can use rodenticides, but they dont kill mice immediately. This means that the mice will likely pass away in their nest. If the nest is inside your wall, then you’ll have dead mice rotting in your wall.
Dead mice in a wall can attract flies, or cause a bad smell which can last for weeks.
Eventually the mice will rot and the smell and the flies will be no more.
So, the decision is yours as to whether you are willing to risk bad smell and flies to get rid of the mice.
If we ignore the smell/flies issue, and just focus on the matter of getting rid of the mice, then the most effective solution will always be a two pronged approach using both rodenticides and traps.
Identify and Remove Nests (if Possible)
If you suspect where the mice are nesting, try to access and remove the nest.
Gaining access to the inside of a cavity wall or stud wall will usually not be possible without wrecking the wall (which we don’t advise). In such cases your strategy will be to pick the mice off one by one with traps. This way, you will eliminate the mice and there won’t be any dead mice carcasses rotting in the walls.
If you can access the nest:
If you are able to access the nest, then wear gloves (and a face mask if possible) when handling nesting materials or droppings, as they can carry harmful bacteria. If you find a nest (it will often look like a ball or pile of shredded paper, fabric, and debris), place it carefully into a sealed plastic bag.
Remove all bedding material the mice have gathered.
Disinfect the entire area afterward with a household disinfectant or a bleach solution to kill germs and reduce the scent trail.
Avoid sweeping or vacuuming dry droppings directly, as this can send harmful particles into the air — instead, dampen the nest area by spraying disinfectant, before scooping everything up.
Health Risks and Dangers of Mice in the Walls
Mice might be small, but an infestation can pose real health risks and dangers in your home. It’s important to understand why you shouldn’t ignore mice in your walls:
Disease and contamination
Mice are known to spread various diseases through their droppings, urine, and saliva. For example, Salmonella bacteria can be present in mouse droppings, which may contaminate your food preparation surfaces and food, leading to food poisoning. In more serious cases, rodents can carry Leptospirosis (Weil’s disease) or viruses like Hantavirus in some parts of the world. While severe diseases are relatively rare, the risk is still there – especially if you’re cleaning areas with droppings without proper precautions. Mice also carry parasites like fleas, ticks, and mites which can transmit illnesses.
Allergies and asthma
The droppings and urine of mice can dry out and become particles in the air, potentially triggering allergic reactions or asthma in sensitive individuals. Even after the mice are gone, remnants of an infestation can continue to cause indoor air quality issues if not cleaned.
Food spoilage
Mice will roam your kitchen cupboards chewing into packaging and contaminating food with waste. If you see any signs of gnawing or droppings near food, those food items should be thrown away. Consuming food or water contaminated by mice can make you very ill.
Property damage
Mice have a constant need to gnaw. In walls, they may chew on wooden structures and even electrical wiring. Chewed wires create a serious fire hazard. Mice can also damage insulation, plasterboard, and stored items. Over time, a few mice can cause surprising amounts of damage behind the scenes. If they die in the wall, they can also cause strong odours and attract flies.
Rapid breeding
A pair of mice can multiply quickly. A single female mouse can have multiple litters in a year (often 5-10 litters, with around 5-6 pups each). Those offspring can breed within weeks. This means what starts as a couple of mice can turn into dozens in a matter of months. The larger the infestation, the greater the health risks and damage, and the more challenging it becomes to eliminate.
Because of these risks, addressing a mouse infestation swiftly is important.
The longer mice live in your walls, the more droppings and urine will accumulate (increasing contamination), and the more they will chew through your home. Acting quickly protects your family’s health and prevents costly damage to your property.
When to Call Professional Pest Control
DIY methods can be very effective for a small number of mice, but sometimes an infestation persists despite your best efforts.
So, when should you call in professionals?
If you continue to hear noises in the walls, find new droppings, or notice damage even after weeks of trapping and sealing, it’s likely time to seek expert help.
A professional pest control technician can assess the situation and implement more advanced solutions.
Professional pest control services (such as those offered by Merlin Environmental Solutions) have experience and tools that go beyond DIY measures. Experts can identify all the entry points you might have missed and locate hidden nests deep in wall cavities or attics.
They also have access to stronger rodenticides (poisons) and specialised bait stations not available to the general public, which they use safely and strategically. Moreover, pest control professionals understand mouse behaviour and will use an integrated approach — combining sealing, trapping, and baiting in the most effective way for your specific situation and requirements.
Another advantage of calling professionals is safety and peace of mind. They will ensure that any treatment laid out is safe for your household (including pets and children) and that dead rodents are properly removed to avoid odour or secondary poisoning risks. Professionals can also give you tailored advice on preventing future infestations based on how the mice entered your property.
Mice infestations can happen to the cleanest of homes and sometimes DIY methods just aren’t enough for a stubborn infestation. An experienced technician can usually resolve the issue faster and more thoroughly, saving you time and stress.
Professional Mouse Pest Control Services
For fast, effective relief from a mouse infestation, consider reaching out to a professional pest control company. Merlin Environmental Solutions is a UK-based mouse control expert that offers comprehensive mouse pest control services. Our team is equipped to handle mice in walls or any other part of your property safely and efficiently. We use proven methods to eliminate mice and can put in place long-term solutions to stop them coming back.
Remember: the sooner you tackle a mouse problem, the easier it is to get under control. By following the steps in this guide, you can take positive action against mice in your walls.
