You come home, open the front door and there it is. A stale, damp, slightly earthy smell that wasn’t there in the summer. A musty smell in the house is one of the most common things people search for once October starts. It’s rarely a mystery, so you can usually get rid of the musty smell once you find the source. Windows stay shut, washing dries indoors, and moisture hangs around with nowhere to go.
The good news is that most causes are easy to find and fix. Here are the eight we see most often in London homes, and what to do about each one.
What causes a musty smell in a house?
Almost every musty smell in a house comes back to one thing: moisture that isn’t drying out. Damp air lets mould and mildew grow, often in places you can’t see, and those tiny growths give off the smell. Dust, old fabric and poor airflow make it worse.
In autumn, the conditions line up. The heating isn’t on all the time yet, the evenings are cooler, and nobody wants to open a window. Indoor humidity climbs above 60%, and that’s where the smell starts.
1. Hidden mould and condensation
This is the number one cause. Check the places that stay cold and still: behind wardrobes and beds on outside walls, the corners of ceilings, under the sink, window frames and the back of cupboards. A grey or black bloom, even a small one, can make a whole room smell.
Clean it off, dry the surface and deal with the moisture behind it. Our full guide on condensation and mould walks you through it step by step.
2. Carpets and rugs
For example, carpets soak up moisture from the air, spills, pets and wet shoes. Once the fibres and the underlay stay a little damp, they start to smell, especially in ground-floor flats and basements. A musty smell in the house that’s strongest at floor level usually points here.
Vacuum slowly and often, including under furniture. If the smell stays, a carpet steam clean gets into the fibres properly. Just make sure the room is well ventilated afterwards so the carpet dries within a few hours, not a few days.
3. Sofas, curtains and soft furnishings
Fabric also holds on to smells. Sofas collect sweat, food and pet hair. Heavy curtains trap condensation from the windows behind them. Cushions and throws sit in the same damp air all autumn.
Wash anything with a removable cover. Take curtains down once or twice a year, or at least hang them out on a dry, breezy day. For sofas and armchairs, upholstery cleaning removes what a vacuum can’t.
4. The washing machine
If your clothes come out smelling worse than they went in, the washing machine is probably the cause of the musty smell in the house too. Water sits in the rubber door seal and the detergent drawer, and mould grows there. Cleaning both is often enough to get rid of the musty smell.
- Pull back the door seal and wipe out the grime and hair trapped inside.
- Take the detergent drawer out and scrub it.
- Run an empty hot wash (60°C or above) once a month.
- Leave the door and drawer open after every wash so they can dry.
- Take wet washing out as soon as the cycle ends.
5. Washing dried indoors
Clothes that dry slowly on an airer in a closed room often come out smelling damp. The water they give off also raises the humidity in the whole flat. Dry laundry near an open window or in the bathroom with the fan on, and use a dehumidifier if you can.
6. Wardrobes and drawers
Clothes packed tightly into a wardrobe on a cold outside wall are a classic source of that stale, musty smell. The air inside never moves, so the smell builds up. Leave a small gap between the wardrobe and the wall, don’t overfill it, and open the doors now and then. Never put anything away that’s even slightly damp.
7. Drains and sink traps
A smell that’s worse in the kitchen or bathroom may be coming from the plughole. Hair, soap and food build up in the trap under the sink. Pour a kettle of hot (not boiling) water down, clean the plug and overflow, and if you’re comfortable doing it, unscrew the U-bend and clear it out. Sinks and showers you rarely use can also dry out and let sewer smells through, so run the tap for a minute every week or two.
8. Dust and general build-up
Dust also holds on to smells, especially in autumn with the windows shut. Skirting boards, the tops of doors, lampshades, radiators and the gaps behind furniture all collect it. If you haven’t already, read our guide on how to clean radiators before the heating stays on for winter.
How to get rid of a musty smell for good
However, air fresheners and scented candles only cover it up. To get rid of the musty smell in the house, you need to take away the moisture and the build-up that cause it.
Open windows every day. Ten to fifteen minutes in the morning, even when it’s cold, replaces damp air with dry air.
Watch the humidity. A cheap hygrometer shows you the level. Then keep it between about 40% and 60%. A dehumidifier helps if you’re always above that.
Use your extractor fans. Bathroom and kitchen fans should run while you shower or cook and for a while afterwards. If a fan barely moves air, its filter probably needs cleaning.
Keep the heating low and steady. Cold walls attract condensation. A steady background temperature does more than short bursts.
Use bicarbonate of soda on fabrics. Sprinkle it on carpets or mattresses, leave it for a few hours and vacuum it up. It absorbs odours instead of hiding them.
Do a proper deep clean. Sometimes the only real fix is to clean everything properly, once, and then keep on top of it. A deep clean covers the kitchen, bathrooms, skirting boards, inside cupboards and behind furniture. After that, regular cleaning keeps the smell from coming back.
When a musty smell means something bigger
If you’ve cleaned, ventilated and dried everything and the smell is still there, there may be damp in the building itself. Signs to look for:
- peeling wallpaper or bubbling paint
- a tide mark on the lower part of a wall
- a damp patch that grows after rain
- a smell that’s strongest under the floor or in one corner
These can point to rising damp, a leak, a blocked gutter or blocked air bricks under the floor. A cleaner can’t fix those. If you own the home, a damp surveyor can find the cause. If you rent, report it to your landlord in writing with photos. Serious damp is their responsibility to fix, and GOV.UK sets out what landlords must repair.
Before winter, it’s also worth getting the gutters cleared. Overflowing gutters soak the brickwork, and that damp finds its way inside.
Musty smell questions
Why does my house smell musty all of a sudden?
It usually happens when the weather turns cooler and windows stay shut. Moisture from cooking, showers and drying clothes builds up and lets mould grow in hidden spots. Check behind furniture, under sinks and around windows first.
Is a musty smell in the house harmful?
The smell itself comes from mould and mildew. Living with damp and mould can affect your breathing, especially for people with asthma, allergies or weak immune systems. Find and remove the source rather than covering it up.
How do I find where a musty smell is coming from?
Go room by room and sniff close to carpets, soft furnishings, the backs of wardrobes, sink cupboards and the washing machine seal. The source is usually where the smell is strongest and the air moves least.
Does a dehumidifier get rid of a musty smell?
It helps a lot, because it removes the moisture that mould needs. It won’t remove mould that’s already growing, so clean that off first and then use the dehumidifier to stop it coming back.
Can carpet cleaning remove a musty smell?
Yes, if the carpet is the source. Steam cleaning lifts the dirt, bacteria and residue that hold the smell. The carpet has to dry quickly afterwards, so keep the room ventilated.
Can’t find the source or don’t have time to deal with it? Book a deep clean and we’ll go through the whole home, or get in touch and tell us what you’re noticing.
