While the visible signs of damp are more easy to spot, if there's a whiff of something unpleasant lingering in your home, you might be wondering what damp smells like in case it's the cause of your problematic odour.
After all, even though the word 'musty' is the one we most commonly associate with damp and mould, is this the only smell it gives off or could it be a case of mistaken identity?
We asked experts what does damp smell like, why does it smell and how to identify if your offensive odour is actually being caused by damp or something else.
What does damp smell like and is it always the same?
Ask the person next to you, 'what does damp smell like?', and there's probably a common thread of replies. Eau de dog, musty, earthy, yesterday's gym bag and wet clothes are all phrases you'll probably hear bandied around.
But, is this the only smell it can give off, or are there other smells associated with damp?
"Damp generally has a musty, stale smell," says Michael Zohouri, founder of Pyramid Eco. "I’d describe it as similar to that earthy scent you get if clothes are left wet in the washing machine. It tends to hang in the air and doesn’t go away with normal cleaning or air fresheners. Once you’ve smelled it, you tend to recognise it straight away," he adds.
And, while you may experience some variation in the smell, it's generally where the damp is coming from that makes the difference, not what type of damp or mould it is.
"The character and intensity of the odour vary depending on the source of moisture, such as condensation, rainwater penetration or below-ground dampness, as well as the material affected, duration of the problem and any microbial growth it may support," explains Douglas Kent, technical and research director at The Society for the Protection of Ancient Buildings (SPAB).
"Trapped dust, organic matter and the type of surface can also subtly influence the smell, making each situation unique," he adds.
Michael Zohouri is the founder of Pyramid Eco, a UK-based home energy and ventilation specialist. He has over 10 years of hands-on experience solving damp, mould and air quality issues through targeted insulation upgrades, ventilation systems and moisture control solutions.
Douglas Kent is a chartered building surveyor specialising in building conservation. He has worked in the public and private sectors, offering advice on historic buildings to a range of organisations such as the Ministry of Defence and English Heritage. His technical knowledge is underpinned by formal qualifications, including an MSc in the Conservation of Buildings, and the practical experience he has gained from leading volunteers' old building working parties as well as the renovation of his own Grade I listed, medieval, timber-framed house. He publishes and lectures regularly on building conservation and has contributed to various radio and television programmes. He also serves on many committees for organisations devoted to the historic built environment. In 2013, he became Chairman of the Hundred Parishes Society.
Why does damp smell?
The next point to tackle is why damp smells.
"The smell comes from mould and bacteria growing in areas where moisture has built up," explains Michael. "What you’re actually smelling is the spores and gases being released into the air as materials like plaster and fabric are being broken down.
"It also usually means the area has been damp for a while. If you can smell it, there’s a moisture problem that needs sorting."
Damp smell vs mould odour
Before you start calling in a damp specialist, it's also important to consider if the smell you are experiencing is caused by damp or mould. And, while it's easy to think that they may have the same pungent pong, you might be surprised to find that they don't.
"Mould and general dampness do not smell the same," says Douglas Kent. "While dampness is typically described as musty, earthy or slightly sour, the smell of mould is usually stronger, more pungent and often mushroom-like.
"This distinctive odour arises from volatile organic compounds produced by mould as it grows. A musty smell does not always indicate visible mould, but a stronger, mushroomy odour can signal that mould growth is already occurring – even if it isn’t yet visible – highlighting the need to identify and address the underlying moisture source," he warns.
"Black mould (Stachybotrys) is the type of mould that most homeowners will encounter," expands Michael Zohouri. "It’s the type of mould you get around uPVC windows and in bathrooms and it tends to have a slightly stronger, more sour smell. White moulds are usually milder but still give off a damp, musty scent."
"Mould growing on wood or plasterboard, however, usually smells quite sharp compared to mould growing on carpets," he adds.
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Can you smell damp before you see it?
So at what point does damp smell? Is it before or after we see it appear on our walls or notice damp patches on ceilings?
"It is possible to notice dampness through smell before any visible signs appear," confirms Douglas Kent. "Even when surfaces look dry, moisture within walls, floors or ceilings can interact with materials and organic matter, releasing subtle volatile compounds into the air.
"This early odour may indicate hidden moisture or developing microbial activity that hasn’t yet caused staining, peeling or decay. Paying attention to such smells enables early investigation and intervention, potentially preventing more serious structural or health problems later."
It's why early investigation is key. But where to look?
"In terms of mould, growth tends to start behind furniture, under flooring and in other places you don’t tend to look," says Michael. "So if you can smell it and can’t immediately see the source, it’s a good idea to investigate the hidden mould hotspots that are out of sight," he suggests.
"Check the areas that are most likely to trap condensation," he continues. "Look behind any large furniture that’s up against an outside wall. These walls are colder and more prone to condensation. Look in corners, around window frames, and under units.
"If the smell is stronger upstairs it could be due to poor insulation or another issue in the loft space," he adds. "You’d be surprised how often we find bathroom extractor fans that have been vented into the loft by mistake.
"But, if you still can’t find anything obvious, it might be inside a wall or you could have mould under the floor or damp. At that point, it’s worth getting a damp survey before the problem spreads," advises Michael.
Could the damp smell be something else?
If you are sure you don't have a problem with damp, it could also be that your odour is actually caused by something else say the experts.
"Several non-dampness sources can produce smells easily mistaken for dampness," confirms Douglas Kent. "Drains can frequently smell sulfurous or rotten and are worse after water use. Blocked or wet chimneys give stale or acrid odours, especially in rain.
"Old furnishings, carpets or curtains can retain musty, dusty smells," he adds, "and modern materials like MDF, vinyl or sealants may also give off sharp, chemical odours. And don't forget that animals or insect infestations also create musky, earthy smells.
"To identify the true source, localise the smell in the building, note when it appears, ventilate the area, check surfaces and voids, and consider moisture pathways," suggests Douglas. "Real dampness usually coincides with visible signs or repeatable moisture patterns."
Managed to sniff out the location of your damp and discovered you need some extra damp proofing? Find out what you can expect to pay for damp proofing costs, and once the problem is resolved, check out the dos and don'ts for painting over damp inside your home.
