The developer says the damp is condensation, not a defect. Who decides?

In the end, a technical expert decides, and in practice, whoever has a written report first is in the stronger position. The guarantee periods on a new build are ten years for the structure, three years for the installations and one year for the finishes. A damp problem only falls inside these periods if it comes from a construction fault. Condensation caused by how a flat is used and ventilated does not count. This is why an independent inspection with photographs and dates is more useful than an argument, and why the first-year snagging window matters so much.

Is black mould in the corner dangerous?

It is a health issue rather than a building emergency. Mould spores can make asthma, allergies and breathing problems worse, and children and older people are affected more. Clean it, then fix the cause, because cleaning alone means it will return every winter. If someone in the family has asthma, treat a persistent damp problem as a reason not to buy, not as a small project.

How do I know whether the flat has a damp problem if I view it in May?

Look at the places that keep the evidence: the backs of wardrobes, the ceiling corners, the wall base, the store room, the ceiling under the terrace. Damp leaves marks that survive a dry spring, and fresh paint in exactly these places is itself a warning sign. Then ask two questions in writing: has any damp ever been treated here, and what did the community last spend on the roof, the terraces or the facade.

Can I ask the seller to fix damp before completion?

Yes, and this is often the better outcome for both sides. Make sure the cause is identified, rather than just painting over the stain. Agree in writing what will be done and by whom, and have it checked before you sign, not after. If the work cannot be finished in time, the alternative is a price adjustment based on a real quote, not a round number.

Are new builds immune to this?

No, but they are in a much better position. The code has required moisture protection since 2006, and post-2010 buildings have double glazing, insulation and ventilation built in, so condensation is far less likely. When something does go wrong, it is usually a defect with someone responsible for it. What a new build does not do is stop a closed flat from getting humid over a winter. That part is still your responsibility.

Guides

Humidity in an apartment on Costa del Sol

In 30 seconds

Damp on the Costa del Sol is usually not a leak. It is condensation: warm, humid air meeting cold surfaces in an empty flat with thin walls. This is why the damp season here is November to February, not August. It is also why a flat that was perfect in May can smell of mould in January.

Inside the roomOutside

Warm, humid indoor air: This is the room side. It holds moisture that a cold wall cannot hold.
The wallUninsulated, single skin: Cold enough on its inner face to drop below the dew point on a winter night.
The dew point: The point where air meeting the cold surface releases its moisture as condensation, not as a leak.
Outside: Cooler night air. This is the real reason the wall’s inner face runs cold.

A cold, uninsulated wall meeting warm indoor air: this is where the dew point sits, and where the mould appears.

Why is winter the damp season here, not summer?

Buyers expect a damp problem in August, when it is hot and the sea is warm. The published figures say the opposite. These are AEMET’s own normal values for Málaga Airport, measured over the 1981 to 2010 period. They explain why a closed-up flat suffers between November and February.

Months	Mean relative humidity	What it does inside a closed flat
November to January	71 to 72 %	The worst combination: humid air outside, cold walls inside, no heating and nobody opening a window. This is when mould appears in ceiling corners and behind wardrobes.
February to March	67 to 68 %	Still humid and still cold at night. Damage caused in December is usually discovered now, by whoever visits first.
April to May	59 to 63 %	The flat dries out and the walls warm up. This is also when most viewings happen, which is exactly why a viewing tells you so little about damp.
June to July	58 %	The driest months of the year on this coast. Air conditioning also removes moisture while it cools, so an occupied summer flat stays dry.
August to September	61 to 65 %	Humidity rises with the sea temperature, but it stays below the winter figures. What people remember as "humid August" is heat plus humidity, not the peak humidity level.
October	70 %	The turning point. Autumn rain arrives, the building cools, and the damp season starts again. This is the month to prepare the flat for, not December.

Relative humidity is only half the story. Condensation happens when air meets a surface colder than its dew point, so surface temperature is the real factor. An unheated flat in January has cold outside walls, and that is why the damp appears there, and not in the middle of the room.

August

Mean humidity: 61 to 65 %
Wall surface: Warm, near air temperature
Building occupancy: Occupied, air conditioned
What happens: Dry: the AC removes moisture while it cools

January

Mean humidity: 71 to 72 %
Wall surface: Cold, often below the dew point
Building occupancy: Empty, unheated
What happens: Condensation on the coldest surfaces

The same flat, six months apart, using the AEMET figures from the table above. Occupancy and heating change as much as the weather does. The annual mean of 65 % and the December peak of 72 % are yearly figures, not figures for either of these two months.

Sources

AEMET: normal climate values, Málaga Airport station, reference period 1981 to 2010, monthly average relative humidity ↗

Is the coast really more humid than inland Spain?Yes, but the number is lower than the internet says. Málaga Airport averages 65 % over the year, peaking near 72 % in December, against much drier inland figures. The coastal problem is not an extreme humidity level. It is a mild, humid winter combined with buildings designed for summer, plus salt in the air, which attacks materials in a separate way.

What kind of damp are you looking at?

These four kinds of damp look similar, but they are not the same problem. They do not have the same fix, and they are not always the same person’s bill. Almost all coastal damp is the first kind below.

CondensationBy far the most common
Where it appears
Ceiling corners, cold outside walls, behind furniture, inside wardrobes.
What it looks like
Black spotted mould, water droplets on glass in the morning, a musty smell in a closed flat.
Who typically pays
You. It is caused by air and temperature, not by a building fault, and ventilation plus heat usually solves it.
Penetrating dampFrom outside
Where it appears
A patch, not a wide spread: under a window, below a terrace, or on a wall exposed to driving rain.
What it looks like
Gets worse after rain and dries slowly. A clear stain rather than general dampness.
Who typically pays
Whoever owns the part the water came through: often the community, if it is a shared roof or facade.
Rising dampFrom the ground
Where it appears
A band along the bottom of a wall. Ground floors, garages, storage rooms, older houses.
What it looks like
A consistent height, salt crumbling the plaster, paint lifting off the wall.
Who typically pays
You. This is a build-era question: older construction often has no damp-proof barrier at all.
A leakFrom a pipe
Where it appears
In one place, often a ceiling under a bathroom.
What it looks like
Can appear at any time of year. If a patch appears in July, it is not condensation.
Who typically pays
Depends on the source. It needs to be found before it can be repaired, and your policy may or may not cover the search.

The quick test is season plus shape. Winter, on cold surfaces, spread over an area: condensation. After rain, in one place, from one direction: penetrating damp. A band at the bottom of a wall: rising damp. Any time of year, under a wet room: a leak.

Damage from a shared part of the building, such as a roof, a shared terrace above, a facade or a shared pipe, is handled by the community and its insurance, not yours. It is worth checking this boundary before you reserve, not after.

What property insurance covers

Does damp on the bathroom ceiling mean the flat above is leaking?Not necessarily, and this is the most common wrong assumption. A bathroom with no window and a weak extractor fan produces enough moisture on its own to blacken a ceiling corner, and that is condensation. A leak from above is usually a clear patch. It can appear at any time of year and often shows a tide line. Before you write to your neighbour, run the extractor fan for twenty minutes after every shower for two weeks and see whether it changes.

Why are coastal Spanish buildings prone to damp?

None of this is bad workmanship. These buildings follow a building tradition designed for heat and sun. That tradition is then used in a climate that also has a humid, cool winter, by owners who are not there for it.

No damp-proof barrier in older constructionSpain’s building code only gained a specific rule against moisture in 2006. That rule covers walls and floors touching the ground, as well as facades and roofs. Buildings built before it often have no barrier at all between the ground and the wall, which is exactly the condition that causes rising damp.
Roofs without guttersFlat roofs and terraces here often drain straight off the edge instead of into a gutter and a downpipe. Rain then runs down the facade and soaks the base of the wall, again and again, in the same place.
Decorative tiling at the splash zoneA tiled band at the bottom of a wall looks good but traps moisture behind it. Once water is inside the wall, a waterproof finish stops it drying outwards. So it dries inwards into your flat instead.
Single glazing and thin insulationCold glass and cold walls are surfaces where condensation forms. An older coastal block with original aluminium window frames and no thermal break has a cold spot around every window. This is why mould appears at window edges and lintels first.
Habitable space under a terraceA tiled terrace over a bedroom is really a flat roof with furniture on it. Its waterproof layer wears out over time and its drains can block. When it fails, the ceiling below is usually the first place anyone notices.
Salt and ultraviolet lightWithin a few hundred metres of the sea, salt attacks metal fixings, hinges, screens, railings and anything chrome-plated. Strong sun also destroys sealants, plastics and outdoor fabrics much faster than in central Europe. Materials that would last ten years elsewhere can look worn out in two or three years. This is a maintenance fact, not a defect.

Sources

BOE, Royal Decree 314/2006: Technical Building Code, basic requirement HS 1 for protection against damp ↗

Which build era changes the risk?

This is the practical version of everything above. Two apartments at the same price on the same street can come from two different building generations, and the damp risk mostly depends on which one.

1960sToday

1960s-70s coastal blocksNo damp-proof barrier
1980s-90s urbanisationsPre-code, better built
2000s, up to the crisisWide quality range
Post-2010 new buildsInsulated, ventilated

CTE damp-proofing standard begins: 2006

Building generations on this coast, from the 1960s to today, with the 2006 moisture-protection standard marked.

The eraWhat to expect

1960s and 1970s coastal blocks: Built fast for early tourism. Usually no damp-proof barrier, single glazing, minimal insulation, flat roofs that have been patched several times, and shared pipework of the same age. Many have been well maintained by their communities, and the good ones are fine. The real question is what the community has spent, and that is written in the meeting minutes.
1980s and 1990s urbanisations: The classic Costa del Sol resale property. Better built, but still built before the moisture and thermal rules existed. The recurring problems are terrace waterproofing over habitable rooms, wall bases on the weather side, and window edges. Ask what has been replaced, and when.
2000s, up to the crisis: A huge amount was built quickly in this period, and the quality varies a lot. Anything finished from 2007 onwards should have been designed under the current code, which sets different moisture rules at ground level, on facades and on roofs. The year of the building licence matters more than the year of the sale.
Post-2010 new builds: Double glazing, thermal breaks, insulation, mechanical ventilation and a moisture-protection standard built in. Damp here is usually a defect rather than a normal condition. This means it is someone else’s responsibility under the guarantees, not yours to manage.
The recently reformed flat: The one to look at most carefully, in any era. Fresh paint and new tiling can mean a real improvement, or they can hide a problem. Look for painted-over patches at a consistent height, new plasterboard on only one wall, a boxed-in section that hides something, and a smell that does not match the finishes. Ask what was repaired, and ask for the invoice.
A property that has stood empty for years: Different from all of the above. No ventilation, no heating, and often no maintenance for several winters, so condensation damage builds up over time. It is often repairable, and it is a genuine reason to negotiate the price. It is also why the price looked good in the first place.

How do you keep an empty flat dry from another country?

A second home closed from October to June is not the same building you viewed in May. Everything below works, it is cheap, and most of it can be set up on the last day of a visit.

A dehumidifier on a humidistat, not a timerSet it to run only when the air passes a set level, aiming for 40 to 60 %. Connect the drain to a waste pipe so nobody has to empty a tank.
A hygrometer you can read remotelyA cheap sensor that records temperature and humidity and sends the data to your phone. This is the single best thing an absent owner can install.
Let the air moveKeep interior doors open, wardrobe doors slightly open, and furniture away from outside walls. Mould grows where the air stays still.
Do not leave the flat sealed and unheated all winterA low background heating setting costs less than the repair would. Where that is not possible, the dehumidifier needs to stay connected to power.
Somebody has to open the windowsTen to fifteen minutes of airing the flat, several times over a winter. This is the one part nobody can automate.
Prepare properly before you leaveDo not drain anything you will need, and leave the electricity connected. Turning off the power to save small standing charges is how a dehumidifier stops working.

None of this requires a paid service, and we would rather you did it yourself than bought something you do not need. What a paid service adds is a person: someone who goes in, opens the windows, empties nothing, reads the hygrometer, and tells you about a problem in February rather than in July.

Property management

Is a dehumidifier enough, or do I need building work?For condensation in a reasonably sound flat, ventilation plus a dehumidifier plus keeping surfaces warm solves it in most cases. What a dehumidifier cannot do is stop water coming in from outside or up from the ground. If a patch keeps coming back in the same place after rain, or sits in a band at the bottom of a wall with salt in the plaster, that is a building problem. Drying the air will only hide it.

What you can see in twenty minutes on a viewing

Take this list to a viewing, or send it to whoever is viewing for you. A phone torch is the only equipment you need. The wardrobes and the ceiling corners tell you more than the terrace view.

Where to look	Why there	What a bad sign looks like
Inside the flat
Ceiling corners, especially in bathrooms and bedrooms	This is the coldest point of the room, and the least ventilated.	Black spotted mould, or a corner painted a slightly different white from the rest.
The outside-facing wall, and the north side	It stays the coldest and gets the least sun.	A cool, damp feel to the plaster, spotting, or paint that has lifted in small blisters.
Window reveals, lintels and the underside of sills	Old aluminium frames create a cold spot and a path for water.	Mould around the window, staining under the sill, rotten seals, or condensation marks on the glass edge.
The bottom 40 cm of walls and the skirting	Rising damp always appears at a consistent height.	A band of discoloration or salt, crumbling plaster, or skirting that has been replaced on only one wall.
The smell, before anybody opens a window	It is the most reliable check you have.	A musty smell in a flat that has been aired and cleaned for the viewing, or a strong air freshener.
The places people do not open
Behind and inside the wardrobes	Still air against a cold outside wall is the classic place mould grows.	Mould on the back panel, on stored fabric, or a wardrobe that cannot be moved.
Under the sinks and inside the bath panel	Slow leaks happen where nobody looks.	Swollen chipboard, water staining, or a suspiciously new cupboard base.
The ceiling directly below a terrace	A terrace over a room is really a flat roof with tiles on it.	Any stain, any hairline crack following a line, or any fresh paint on that ceiling alone.
The store room and the garage	Below ground, unheated and unventilated: the worst case in the building.	Mould on stored items, a tide line, rusted metal, or a dehumidifier already running in the corner.
Outside and communal
The base of the facade and any tiled splash band	This is where roof water lands, and where it cannot dry out.	Repeated repairs, staining below a roof edge with no gutter, or damaged tiles at the wall base.
Terrace drains, upstands and the tiles at the threshold	Waterproofing fails at edges and outlets, not in the middle.	A blocked outlet, tiles laid level with the door threshold, or silicone used instead of a proper detail.
The community’s last three years of minutes	Roof, terrace and facade works are voted on and paid for at these meetings.	Repeated damp problems mentioned, a postponed roof repair, or a levy that was rejected.
What has been repaired, and the invoice	A real repair has a document. Covering up a problem does not.	A recent redecoration nobody can explain, and no paperwork for any of it.

This list helps you narrow down a shortlist, and it does not replace a survey. On a property you are serious about, a technical inspection is a separate, referred service with a written report, and that report is what you negotiate with.

Technical property inspection

Damp in a communal element, or inside your own flat

The same stain on the same wall can mean a different bill, depending on where the water came from. It is worth finding this out before you reserve, not after you own the property.

	Common area of the building	Your apartment
Typical cause	The roof, the terrace above if it is shared, the facade, a shared pipe, a shared drain, a retaining wall.	Condensation, your own plumbing, your own terrace, your own windows and your own ventilation habits.
Who pays	The community, from the fee or from a special charge. Spanish property law requires it to carry out the work needed to maintain the shared parts.	You, unless it is a construction defect still inside the guarantee periods, or a claim on your own policy.
How you find out before buying	The minutes of the last three annual meetings, the community’s accounts, and a direct question to the administrator about planned works.	The viewing checklist above, and a technical inspection on a property you are serious about.
What can go wrong	The work is agreed but not funded, or funded by a charge that lands after you complete. Ask specifically what has been approved but not yet paid for.	A cosmetic repair that hides a real, ongoing cause, which then becomes your problem.
What to do about it	Get any planned works and any approved charge in writing before you reserve. Your lawyer checks community debts as standard.	Get a price for the repair, or ask for it to be done before completion and checked afterwards.

From experience

The property that was older than its photographs

This is one of our own cases, and the reason we wrote any of this down. At the visit, the property was simply much older than the listing photos suggested. Nothing had been faked. The photographs were real. They were just doing what photographs do: showing a room after it has been cleaned, lit and framed carefully. Age shows up in the places a camera is pointed away from, and on this coast those are the same places damp shows up: the wall base, the window edges, the backs of wardrobes, the store room.

That is the whole reason to have someone stand in the property with a torch before you get on a plane.

Video tours

Frankly

What we will not tell you

What a repair costs. We do not publish euro figures for drying a wall, re-plastering a base, or waterproofing a terrace, because the honest range is very wide and we would only be guessing at a middle figure. Get a quote based on a written inspection report, and that number will be real.Whether damp changes a price, and by how much. In practice, it often does, and how much depends on what the seller knows, what your report says, and how long the property has been listed. We will not print an average figure here, because a made-up percentage is worse than no percentage at all.We do not carry out inspections ourselves. The technical inspection is a separate, referred service done by a qualified person. What you have just read is deliberately the version you can do yourself, for free, before you spend money on anyone.And the part that is nobody’s fault. Salt, sun and a humid winter are simply what this climate does. Materials age faster here, an empty flat behaves worse than an occupied one, and some condensation in a cold January apartment is physics, not a defect. The buildings are not badly made. They were built for summer, which is the season you saw them in.

Most common questions about damp and construction quality

The developer says the damp is condensation, not a defect. Who decides?: In the end, a technical expert decides, and in practice, whoever has a written report first is in the stronger position. The guarantee periods on a new build are ten years for the structure, three years for the installations and one year for the finishes. A damp problem only falls inside these periods if it comes from a construction fault. Condensation caused by how a flat is used and ventilated does not count. This is why an independent inspection with photographs and dates is more useful than an argument, and why the first-year snagging window matters so much.
Is black mould in the corner dangerous?: It is a health issue rather than a building emergency. Mould spores can make asthma, allergies and breathing problems worse, and children and older people are affected more. Clean it, then fix the cause, because cleaning alone means it will return every winter. If someone in the family has asthma, treat a persistent damp problem as a reason not to buy, not as a small project.
How do I know whether the flat has a damp problem if I view it in May?: Look at the places that keep the evidence: the backs of wardrobes, the ceiling corners, the wall base, the store room, the ceiling under the terrace. Damp leaves marks that survive a dry spring, and fresh paint in exactly these places is itself a warning sign. Then ask two questions in writing: has any damp ever been treated here, and what did the community last spend on the roof, the terraces or the facade.
Can I ask the seller to fix damp before completion?: Yes, and this is often the better outcome for both sides. Make sure the cause is identified, rather than just painting over the stain. Agree in writing what will be done and by whom, and have it checked before you sign, not after. If the work cannot be finished in time, the alternative is a price adjustment based on a real quote, not a round number.
Are new builds immune to this?: No, but they are in a much better position. The code has required moisture protection since 2006, and post-2010 buildings have double glazing, insulation and ventilation built in, so condensation is far less likely. When something does go wrong, it is usually a defect with someone responsible for it. What a new build does not do is stop a closed flat from getting humid over a winter. That part is still your responsibility.

Looking at a specific property?

Send us the property