Musty Smell but No Visible Mould: Where to Look

Rung 1: Pin down the smell (free)

Start by narrowing it down. Walk through the house and note which room the smell is strongest in, and whether it comes and goes. A smell that appears on cold mornings or after the heating comes on points to condensation. A smell that stays whatever the weather points to something wet and steady, such as a slow leak.

• Note where it is strongest. Smell the base of wardrobes, the corners of outside walls and the area around the sink and bath.
• Note when it is worst. Cold mornings, after showers, or after rain all suggest different causes.
• Do not rely on the nose alone. BRE warns that dampness is very often misdiagnosed, so treat the smell as a pointer, not a diagnosis.

Rung 2: Check the likely hiding places (free, with care)

GOV.UK guidance names the usual places: the back of wallpaper and panelling, ceiling tiles, the underside of carpets, behind pipes and furniture, and inside heating and ventilation units. Look at the easy ones first.

• Pull furniture off outside walls and look at the wall and the back of the furniture. The Energy Saving Trust says damp is more likely where air cannot circulate, such as behind furniture.
• Look under sinks and around pipes for staining, soft boards or a damp cupboard base.
• Check the extractor fan grille and any vents. GOV.UK lists damaged, blocked or switched-off extraction as a cause.
• Protect yourself before you disturb anything. GOV.UK says removing carpet or wallpaper can release a significant amount of mould spores. Wear a mask, gloves and goggles, keep doors to other rooms shut and keep a window open. If you suspect a large hidden area, stop and get a professional to look.

Rung 3: Find and cut the moisture (cheap)

Mould needs moisture, so finding the source matters more than cleaning. The Energy Saving Trust lists leaking roofs, blocked gutters, plumbing faults, failed appliances and poorly sealed baths and showers as ways water gets in, often where you cannot see.

• Check for slow leaks. Look at the pipework, the washing machine hose and the seals around the bath and shower.
• Log the humidity. A hygrometer in the room for a week shows whether the air stays damp. BRE describes recording temperature and humidity as the most effective way of diagnosing damp.
• Cut moisture at source. Put lids on pans, run the extractor after cooking and showering, and dry washing away from bedrooms.
• Let air move. Leave a gap behind furniture and keep a 10mm gap under internal doors, as the Energy Saving Trust advises.
• Clean what you find. GOV.UK says to use a mould and mildew product in preference to bleach. Our damp diagnosis guide shows how to get the cause checked before paying for treatment.

Rung 4: When mechanical help or a professional makes sense

If the smell persists, the area is large, or you cannot find a source, bring someone in. GOV.UK says people should not assume they can diagnose damp and mould themselves, and that larger areas of mould should be dealt with by qualified professionals. The Energy Saving Trust suggests getting quotes from three TrustMark-certified professionals.

Where there is no leak and the readings stay high in an owner-occupied home with a loft, a Dryzen loft-mounted system is one option. It helps stop the conditions mould and dust mites need but does not remove mould that is already growing, and it does nothing for a leak or rising damp. It is not suitable for rentals unless the landlord authorises the changes.

Mistakes that make it worse

• Masking the smell with air fresheners instead of finding the source.
• Ripping off wallpaper or lifting carpet with no mask, gloves or goggles.
• Using bleach when GOV.UK recommends a mould and mildew product.
• Assuming no visible mould means no problem.
• Putting furniture straight back against a wall that has not dried.

In Chatham and the Medway Towns

We hold no Medway-specific data on hidden mould smells, so we quote none. What we can say from a source is that the homes are of very different ages. Wikipedia gives the population of Hoo St Werburgh as 1,400 in 1891 and 7,725 in 1971, so much of the village is likely to date from the later twentieth century, while Rochester has far older buildings. Find out what your own walls and floors are made of before judging the cause. See our pages for Hoo St Werburgh and Rochester.

Questions we are asked

Related guides

• Damp Smell in Cupboards and Wardrobes: Causes and Fixes
• Furniture Against Outside Walls: Beds, Sofas and Bookcases
• Hygrometer Guide: How to Measure Humidity at Home
• Getting a Damp Diagnosis Right Before You Pay for Work

Local help

• Damp, mould and condensation help in Hoo St Werburgh
• Damp, mould and condensation help in Rochester
• Damp, mould and condensation help in Gillingham

Sources: GOV.UK: Understanding and addressing the health risks of damp and mould in the home; Energy Saving Trust: How to get rid of damp; BRE: Diagnosing the causes of dampness in buildings