Hearing scratching in the walls or under the floorboards? You're not alone – and from October onwards, as the weather dips and rodents head indoors for warmth, it's one of the most common problems we're asked about. Mice and rats are clever, quiet, and often go undetected until they've made themselves at home, so the key is to act fast before a few become a bigger problem.
The message we get more than almost any other is some version of: "I can hear them, and I can see droppings and gnaw marks, but I can't find where they are." That's completely normal – rodents live and travel inside voids you can't see into. And the thing that trips most people up next isn't the traps or the sealant, it's the order you use them in: catch first, or seal first? Get that the wrong way round and you can make the problem worse.
This guide walks through how to confirm what you've got, locate where they're hiding, and get rid of mice or rats safely – with DIY-friendly methods that work, in the right order.
📋 Quick summary: what to do tonight
- Confirm it's rodents – check for droppings along skirting boards, under sinks and in loft corners.
- Don't seal holes yet – set traps and bait stations first, so you don't shut rodents inside the walls.
- Target the runways – place traps tight to skirting lines, behind appliances and near suspected entry points.
- Cut off the food – store food in sealed containers, clear crumbs, and lift pet food overnight.
- Renting or sharing walls? – report it early to your landlord or council and document the signs.
Signs You Have Mice or Rats in Your Walls or Floors
Scratching noises, especially at night, are a strong sign of rodents. Other indicators include:
- Droppings along skirting boards, in cupboards or loft spaces
- Chewed food packaging or small gnaw marks
- Nesting material such as shredded paper or fabric
- Your pets reacting to hidden sounds or spaces
Mice or rats – which is more likely?
- Mice: lighter, faster scurrying; smaller droppings; activity often around kitchens and cupboards.
- Rats: heavier movement; bigger droppings and gnawing; more likely around bins, drains, garages and under decking.
If you're unsure, treat it as "rodents present" and follow the same safe process: trap and control first, then proof.
Heard it in the daytime? Rodents are mostly nocturnal, so scratching during daylight hours is more likely to be squirrels in the loft or birds nesting in a vent or under the eaves – a different job that rodent traps won't solve.
Why Rodents Get Into Walls and Floorboards
Rats and mice are drawn into homes, and more specifically into wall cavities, floor voids and lofts, because they're warm, dark and protected from predators. In our experience it tends to be older buildings that suffer most – solid-wall terraces, period conversions, and properties with plenty of service voids and shared cavities – and there's no one-size-fits-all fix, so you work with the layout you've got. In terraced and semi-detached homes, rodents may also travel between properties via shared walls or joist voids.
No Gaps, but Still Hearing Mice and Rats? Here's What That Means
If you can't find any visible entry points, mice and rats may be moving through:
- Hidden voids under floorboards
- Behind kitchen plinths or bath panels
- Shared cavities in walls or lofts between properties
- Service risers or pipe runs in flats and conversions
In these cases, don't wait to find a visible hole – start by closing the routes into your living space (under sinks, behind kitchen plinths, around internal pipework) and target the suspected runways with traps or bait stations. You may also want to speak to your landlord or neighbours to see if this is something you need to solve together.
If you live in a flat, terrace or semi, rodents can travel via shared cavities and service runs. It's often faster to tackle this as a joined-up job – speak to neighbours or your building manager – and, if needed, ask your local council about pest control support.
How to Get Rid of Mice and Rats in Walls and Floors
The order matters here, and it's where most people go wrong: catch first, then seal. Reduce the rodents inside before you close their exits, or you'll trap them in the walls. Here's the full sequence.
a. Identify the Source
This is the answer to that "I can hear them but can't find them" problem. If there have been no sightings, pinpoint where the sounds are coming from and sprinkle a thin line of talcum powder or flour near floor-level access points, then check for footprints, smears or droppings the next morning to reveal the runways they're using.
b. Inspect for Entry Points
Check for entry points both inside and outside the home – around boiler flues, pipework, air bricks, behind appliances, and in the loft. Mice only need a 5mm gap to squeeze through and rats around 15mm. Take note of potential access routes, but don't seal them yet – you'll use these spots to place your control measures first.
If you seal up the gaps a rodent is using too soon – whether they're on the outside of the building or lead into a wall or floor cavity – you risk:
- Trapping mice and rats inside with no exit, leaving them to die, decompose and emit a smell lasting several weeks
- Making it harder for them to reach bait or traps
- Encouraging them to chew new exit routes into living areas
c. Use Traps or Bait Stations Before Sealing
Before blocking anything, reduce the population with mouse traps, rat traps, and bait stations for added safety, placed near entry points and other areas with evidence of activity. This gives any rodents still inside a chance to interact with your control products instead of becoming trapped in the walls or floors.
Once you no longer hear scratching and signs of activity stop – including no newly trapped mice or rats – for about a week, it's time to proof your property properly.
d. Seal Gaps with Rodent-Proof Materials
After the control phase, it's time to fully rodent-proof your home. There are really two jobs here, and the timing differs. The openings into your living space – gaps under sinks, behind kitchen plinths and around internal pipework – can be closed earlier, since these keep rodents out of your rooms and food rather than sealing them into a void. The building's outer shell and any wall or floor cavities, though, are sealed now, once activity has stopped for about a week – sealing these while rodents are still inside is what risks trapping them in to die and smell. Use rodent proofing products such as steel wool, metal mesh or rodent-proof fillers, and avoid expanding foam alone, as rodents can chew through it easily.
Worth knowing: professional pest controllers often seal and trap at the same time, using one-way exclusion devices (rodent flaps that let rodents out but not back in) and structural know-how to make sure nothing gets sealed in. For a DIY job without those tools, sequencing it – catch first, then close the cavities – is the safer bet.
Be Environmentally Responsible
Only use rodenticides approved for amateur/home use in the UK.
If children, pets or wildlife could access the area, always use tamper-resistant bait stations and consider non-toxic or mechanical options first. Always follow the instructions, and never throw poisoned rodents in regular bins or compost.
Some professionals advise against rodenticides, and we only recommend them as a last resort here, because rodents often retreat into the wall before dying – leaving a messy, smelly problem.
For eco-conscious control, consider humane traps or mechanical options first, which let you release trapped rodents alive away from your home.
Long-Term Mouse Prevention Tips
- Keep all food (including pet food) in sealed containers
- Vacuum regularly and clean behind appliances
- Declutter lofts, sheds and garages
- Trim plants near external walls
- Re-check for new gaps or signs every few months
⚠️ Cleaning up droppings and dead rodents safely
Don't dry-sweep or vacuum droppings – that flicks dust into the air, and rodent droppings and urine can carry bacteria such as salmonella and leptospirosis. Open a window, put on disposable gloves (and a mask), dampen the area with a disinfectant solution, wipe it up with kitchen roll, then double-bag it and put it in the general waste. Wash your hands thoroughly afterwards. Handle any dead rodents the same way, and never put poisoned rodents in food or garden waste.
When to Call a Pest Control Professional
If the scratching persists, or if you find signs of a larger infestation, it's worth calling a pest controller. Professionals can use thermal cameras, smoke tests and more sophisticated baiting strategies for harder-to-reach or multi-property infestations.
FAQs: mice and rats in walls and floors
I can hear them and see droppings, but I can't find them – what now?
That's completely normal – rodents live and travel inside voids you can't see into. Lay a thin line of flour or talc near suspected runways and skirting to reveal footprints overnight, and check loft corners, under-floor edges and behind kitchen plinths to narrow down where they're active.
Is daytime scratching still mice or rats?
Less likely – rodents are mostly nocturnal, so noise during the day usually points to squirrels in the loft or birds nesting in a vent or under the eaves, which need a different approach.
Will mice or rats in the walls leave on their own?
Not reliably. A warm, safe void with food nearby is exactly where they want to be, so they tend to stay until you trap them out and seal the gaps they're using.
Should I block the hole if I can hear them?
Not yet. Seal too early and you trap rodents inside to die and smell – catch first, wait until activity has stopped for about a week, then proof the gaps.
Should I seal the gaps inside or outside first?
Close the openings into your living space first – gaps under sinks, behind kitchen plinths and around internal pipework – to keep rodents out of your rooms and food. Leave the building's outer shell and any wall or floor cavities until activity has stopped for about a week, because sealing those while rodents are still inside risks trapping them in to die.
Do I have to remove the rodents before sealing?
For a DIY job, yes – it's the safer order, because closing a cavity with rodents still inside can trap them in to die and smell. Professionals often seal and trap together, but they use one-way exclusion devices (flaps that let rodents out but not back in) and structural experience to avoid that, which most homeowners don't have to hand.
How can I tell mice from rats by the sound?
Mice tend to sound lighter and faster, sometimes with squeaks; rats are heavier with more gnawing. It's hard to be sure by ear, so droppings are the better guide – mouse droppings are 3–8mm, rat droppings 10–14mm.
The scratching stopped but now there's a smell – what is it?
Usually a rodent that has died inside the void. Ventilate the area, and if the smell persists beyond a few days you may need to locate and remove it, or call a professional.
Final Word
Mice and rats may be small, but they can cause big problems if left unchecked. By spotting the signs early, acting with the right traps, and blocking entry points in the right order – catch first, then seal – you can reclaim your home safely and efficiently.
Need help getting started? Shop our full range of mouse control products and rat control products – everything you need to deal with rodents in walls, floors, or anywhere else they try to hide.
Hear scratching? Don't wait. Start rodent-proofing your home today.
We go to great lengths to ensure that our pest control products are effective, fast & easy for everyone. You may also find our expert mouse guide or expert rat guide useful if you want to learn more about getting rid of rodents from your home or business.
