Damp and mould in Spanish homes in winter: causes and what helps

Many people are surprised to find damp patches and black mould in their Spanish home in winter, even on the sunny Costa del Sol. Homes here are often built to stay cool in summer rather than warm in winter, and a few weeks of rain and cooler nights is enough for condensation to appear. The good news is that most cases can be improved with simple habits. This guide explains the causes, what helps and what to do if you rent.

Why damp appears in winter

Warm indoor air holds moisture from cooking, showers, drying clothes and simply breathing. When that air touches a cold surface, such as an outside wall, a window or a corner behind a wardrobe, the moisture turns back into water. That is condensation, and mould grows where surfaces stay damp.

Older flats, ground-floor homes and properties near the sea are often more affected. So are homes that are only heated now and then, because walls stay cold between short bursts of heat.

Three types of damp to tell apart

• Condensation: water drops on windows, black spots in corners, on ceilings and behind furniture, often worse in bedrooms and bathrooms. This is the most common winter problem.
• Rising damp (humedad por capilaridad): a tide mark low on the walls, flaking paint or salt deposits near the floor, common in ground-floor homes.
• Leaks (filtraciones): a patch that grows after rain or appears near a roof, terrace, window frame or pipe. This needs a repair, not just better ventilation.

Getting the type right matters, because a dehumidifier helps with condensation but will not fix a leaking terrace or a broken pipe.

Measure the humidity

A simple hygrometer, sold in hardware shops, shows the relative humidity in a room. The US Environmental Protection Agency (EPA) advises keeping indoor humidity below 60%, and ideally between 30% and 50%. Check readings in the morning and in different rooms, so you can see where the problem is worst.

Everyday habits that help

• Ventilate every day: open windows for a short time, especially in the morning and after showers or cooking. Use the extractor fan if you have one.
• Dry laundry outside when you can: on the terrace or balcony on dry days. Indoors, use a ventilated room with the door closed.
• Wipe condensation: dry wet windows and frames in the morning so water does not soak in.
• Give walls some air: leave a gap between furniture and cold outside walls, and do not overfill wardrobes on those walls.
• Keep a steady temperature: gentle, regular heating keeps walls warmer than short bursts. Our guide to heating your home in a Spanish winter compares the options.
• Put lids on pans: it reduces steam while you cook.

Dehumidifiers: when they make sense

If humidity stays high even with good ventilation, a dehumidifier can make a real difference, especially in bedrooms, bathrooms without windows and ground-floor homes. A few things to check before you buy:

• Room size: the manufacturer usually states the room size or extraction capacity per day. Choose one that matches the space.
• Type: compressor and desiccant models work differently. Desiccant models are often suggested for cooler rooms, while compressor models are common for general use. Read the product information for the temperature range.
• Tank and drainage: a bigger tank or a hose outlet means less emptying.
• Noise and energy use: check the noise level if it will run in a bedroom, and the power rating if it will run for many hours.

You can compare models in local shops or with online appliance retailers such as Electropolis (ad). Empty and clean the tank regularly, as the manual says.

Cleaning mould safely

The EPA says you can usually clean a small area yourself, up to about 10 square feet (roughly one square metre). Wear gloves, and protect your eyes and airways.

• Fix the moisture first: otherwise the mould comes back.
• Never mix bleach with ammonia: the EPA warns that it can produce toxic fumes.
• Remove it, do not just kill it: dead mould can still cause allergic reactions.
• Do not paint over mould: clean and dry the surface first, or the paint is likely to peel.
• Call a professional for large areas, damage from dirty water, mould you suspect is inside walls, or if anyone at home has health problems. Mould can trigger allergies and asthma, so speak to your doctor if you have symptoms.

If you rent or live in a block of flats

Under Article 21 of Spain’s urban tenancy law (Ley de Arrendamientos Urbanos), the landlord must carry out the repairs needed to keep the home habitable, unless the damage was caused by the tenant. Small repairs due to ordinary wear and tear are paid by the tenant. You must tell the landlord when a repair is needed and let them or their technician inspect it. You may only carry out urgent repairs yourself, after informing the landlord.

• Report it in writing: send photos and dates by email or message, and keep a record.
• Leaks from shared parts: if water comes from the roof, facade or a neighbour, the community of owners or its administrator usually needs to be involved.
• Check your home insurance: many policies include water damage cover. Read the conditions before you start repairs.

For more on tenant and landlord duties, see our guide to rental law in Spain.

FAQ: damp and mould in winter

Is it normal to have condensation on windows every morning?

It is common in winter, but it is a sign that the air inside is humid. Wipe it off, ventilate and check the humidity. If it keeps coming back with mould, look at ventilation, heating or a dehumidifier.

Who pays for mould in a rented flat?

It depends on the cause. Repairs needed to keep the home habitable, such as a leak, are generally the landlord’s responsibility. If the damage was caused by the tenant, the tenant pays. If you cannot agree, a technician’s report can help.

Will anti-mould paint solve the problem?

Not on its own. Clean and dry the surface and deal with the source of moisture first. Painting over mould without doing this is likely to fail.

Useful links

• US EPA: a brief guide to mold, moisture and your home (PDF)
• BOE: Ley de Arrendamientos Urbanos, consolidated text (Spanish)

Disclaimer: This article is general information, not legal or financial advice. Rules and prices change, so check with the official source before you decide. Links marked “(ad)” are affiliate links – NewInSpain may earn a commission at no extra cost to you.