You pull back the bath mat, switch on the kitchen light or move a plant pot, and there they are: a scurry of grey, many-legged little creatures. If you have been typing “why are woodlouse in my house” into Google, you are far from alone. Woodlice are one of the most common creepy-crawlies to turn up indoors, especially as the weather turns cold and wet.
Why Are Woodlouse in My House? The 5 Main Reasons
You Have a Damp or Humid Area
This is the big one. The Royal Horticultural Society (RHS) explains that woodlice can wander in from the garden but are unlikely to survive for long indoors unless they find a damp place to shelter. So if they are staying, something in your home is giving them what they need.
Common culprits include condensation, leaking pipes, rising or penetrating damp, wet towels and bath mats, and poorly ventilated bathrooms, utility rooms and cellars. As Ideal Home reports, an abundance of woodlice is a sign you may have too much moisture, which can lead to bigger problems down the road.
It’s the Cold, Wet Season
Woodlice are most likely to appear indoors in the colder months. Darlington Borough Council’s pest control guidance notes they come indoors mainly during winter and early spring, and that they do not come in to breed. Heavy autumn rain also pushes them out of soggy soil and leaf litter and towards your walls.
Blocked Gutters and Garden Clutter Near the House
BBC Gardeners’ World lists blocked gutters, which provide decaying matter to feed on, and damp patches from condensation or leaks as common reasons woodlice head indoors. Piles of leaves, mulch, logs, stones and flower pots by your doors create a cosy woodlouse colony right on your doorstep.
Gaps, Cracks and Gappy Doors
Woodlice are small and persistent. Gaps under doors, around pipes and in brickwork give them an easy route in. Lancaster City Council’s woodlice advice sheet links indoor sightings to vegetation and suitable shelter immediately outside the house, which is why a tidy, sealed perimeter matters.
They Prefer Damp Over Dark
Many people assume woodlice simply love darkness. Educational experiments from the Nuffield Foundation show that damp is more important to woodlice than dark: they will settle in damp, bright places in preference to dry, dark ones. In other words, light switches will not keep them away. Dry air will.
Are Woodlice Harmful?
No. Woodlice do not bite or sting, and they are not known to spread disease in homes. Lancaster City Council confirms they do not bite, and Darlington Borough Council points out that, despite the name, they do not damage wood. They feed mainly on rotting plant material, and the RHS describes them as largely beneficial in gardens, where they help recycle nutrients.
A few things worth knowing:
- They are decomposers, not destroyers. They feed on dead and decaying plant matter, not your sofa or carpet.
- A female can produce up to 150 eggs (Lancaster City Council), so a damp spot left alone can build up numbers.
- They are a warning sign. The real concern is the moisture behind them, which can encourage mould and affect your property.
How To Get Rid of Woodlice in Your House (Step by Step)
Fix the Moisture Problem First
This is the only long-term solution. Gardeners’ World advises that woodlice will not be attracted to live in a house that is dry and warm, so address the damp or condensation at the source.
- Repair leaking pipes, taps and roof or gutter faults.
- Run extractor fans in bathrooms and kitchens, and open windows regularly.
- Use a dehumidifier in damp rooms; Ideal Home calls it the easiest way to deal with excess moisture.
- Let towels and bath mats dry fully rather than leaving them damp on the floor.
Clear Their Hideouts Outside
Ideal Home’s expert advice is to clear away leaf litter, mulch and soggy wood from around the house foundations so outdoor nesting sites disappear. The RHS and Darlington Borough Council also recommend removing sheltered spots near the house such as flower pots, and keeping gutters clear.
Seal Entry Points
Check for gaps and cracks in walls and under doors, as suggested by Gardeners’ World. Fit draught excluders to external doors and seal gaps around pipes and windows. East Devon District Council also lists sealing entry points and warming up affected parts of the house as helpful steps.
Move Them Outside, Humanely
For a handful of woodlice, simply sweep or scoop them up and place them in a damp spot away from the clean house. Gardeners’ World recommends exactly this, and Lancaster City Council advises that odd woodlice found indoors should simply be placed outside.
Use Insecticides Only as a Last Resort
East Devon District Council notes that insecticide spray or dust can be applied to crevices or damp areas that cannot be properly dried. Treat this as a last resort: if you do not fix the damp, new woodlice will keep arriving. Always follow the product label, and take extra care around children and pets.
When Should You Call a Professional?
Consider getting expert help if woodlice appear in large numbers in every room, if you notice a musty smell, visible mould, peeling paint or soft or discoloured timber, or if the problem returns after you have tackled the obvious causes. These can point to hidden leaks, damp under floors or ventilation problems that a damp surveyor or plumber can diagnose.
Quick Prevention Checklist
- Ventilate bathrooms, kitchens and utility rooms daily.
- Keep gutters, downpipes and drains clear.
- Store firewood, pots and garden debris away from external walls.
- Fix leaks promptly and dry wet floors and mats.
- Seal gaps around doors, windows and pipework.
- Keep soil and mulch levels below your damp-proof course.
Frequently Asked Questions
Why are woodlouse in my house at night?
Woodlice are nocturnal feeders. The RHS notes they hide in dark, damp places by day and move around at night in search of food, so you are most likely to spot them after dark.
Do woodlice mean I have damp?
Often, yes. If they are staying indoors rather than just wandering through, it usually means there is a damp area. Check bathrooms, cellars, under sinks and around windows.
Can woodlice damage my home?
No. They feed on decaying plant matter and do not damage sound timber or fabrics. The damp that attracts them is the thing to watch.
Will woodlice go away on their own?
Possibly. The RHS says they are unlikely to survive for long indoors without damp, and they dry out quickly in dry conditions. Fixing moisture speeds this up.
Are woodlice the same as pill bugs and slaters?
Mostly, yes. The RHS notes woodlice are also known as slaters and pillbugs. Some species can roll into a ball when threatened.
Final Thoughts
So, why have you got lots of woodlice in your house? Almost always, it comes down to moisture, plus easy access from a cluttered or damp exterior. They are harmless visitors, but they are a handy early-warning system for damp. Dry the air, tidy the outside, seal the gaps, and the woodlice will move on.
