Woodworm, termites and damp in Spanish property (carcoma, termitas, humedades) — the invisible defects quietly eating old stone houses, 2026 foreign buyer's guide

The house looks perfect. Whitewashed, thick-walled, a beamed ceiling the agent leans on the word castaño for — four-hundred-year-old chestnut, they say, tapping it. You tap it too. It sounds solid. You buy it. Eighteen months later a builder from the next village stands on a ladder in your dining room, pushes a screwdriver into that same beam up to the hilt, and says the word every foreign owner in inland Spain eventually hears: carcoma. Or worse, and less recoverably: termitas. Or, most quietly and most expensively of all: humedades por capilaridad, damp climbing the walls from a foundation that has been drinking rainwater since the Bourbons.

Nobody who buys an old Spanish house is unaware, in the abstract, that woodworm and damp exist. The problem is that almost nobody who buys one — and by nobody we mean a striking share of the foreign buyers we see in this office — commissions a peritación that inspects for either, understands the difference between the two woodworm species and the two termite species that matter, or reads the damp section of the survey they did pay for. The house is bought on light, view, tiles and Instagram. The invisible defects are inherited on completion day, silently, in the ceiling.

This is the 2026 foreign-buyer guide to the three invisible enemies of Spanish property: woodworm (carcoma), termites (termitas) and damp (humedades). It explains what each one is, where in Spain it thrives, how to spot it during a 40-minute viewing, what a proper diagnosis and treatment cost in 2026 euros, what your home insurance will and will not pay for, and the two lines on a peritación that separate a fair reduction from a plane home.

Why these three, and why they all hit foreign buyers harder

There is a specific reason woodworm, termites and damp punch above their weight in the foreign-buyer market. It is not that Spanish houses are unusually infested — a Norman farmhouse or a Suffolk cottage has the same problems. It is that the Spanish rural stock foreign buyers actually shop for — the stone cortijo in Andalusia, the masía in Catalonia, the caserío in the Basque country, the village house in a pueblo blanco or a Castilian pueblo — is dominated by three construction features that make all three problems worse:

• Structural timber: chestnut, pine or oak beams and joists holding up terracotta rasilla ceilings and clay-tile roofs. Every one of those beams is dinner for either anóbidos (common furniture woodworm) or Mediterranean subterranean termites (Reticulitermes lucifugus).
• Solid stone or tapial (rammed-earth) walls, no cavity, no damp-proof course. The walls behave as wicks: groundwater climbs by capillarity, roof runoff sinks in through the top, and everything meets in the middle.
• A twenty- or forty-year gap since last real occupation. A big share of the rural stock on Idealista and Fotocasa has been either empty or lightly used by an aging widow for two decades. Empty houses in Spain do not gently age; they collapse in slow motion.

Add to this three foreign-buyer patterns and you have the trap. Foreign viewings almost always happen in spring or early summer — the driest weeks of the year, when damp is invisible and termite swarms have not yet emerged. Foreign buyers frequently skip or downgrade the peritación, because the Spanish system does not require a survey and the estate agent will confidently tell you it isn't normal. And foreign buyers buy with their eyes rather than their nose — a house that smells wrong in February smells fine in May, and the human nose is a better humedad detector than any hygrometer.

None of this means you should not buy an old Spanish house. Millions of people live happily in them. It means you should know what you are looking at.

Woodworm (carcoma) — the two species that matter

Carcoma in Spanish is a generic word for any wood-boring beetle larva. In practice, in a Spanish house, you are looking at one of two families:

Common furniture woodworm (Anobium punctatum, plus its close relatives Xestobium and Hylotrupes). The classic carcoma. Small round exit holes of about 1–2 mm in beams, floorboards, doors and furniture, with fine sawdust piles (called serrín in Spanish) below them. The larvae live inside the wood for 2–5 years, tunnelling, then chew their way out in spring as adult beetles, mate, and lay eggs back in the same wood. This is a slow infestation. It eats sapwood by preference, tends to leave the harder heartwood core alone, and in most healthy chestnut or oak beams it is a cosmetic-and-strength issue rather than a collapse issue — unless it has been eating unnoticed for eighty years, which in an abandoned Spanish farmhouse is entirely possible.

House longhorn beetle (Hylotrupes bajulus, carcoma grande). Larger, more aggressive. Oval exit holes 6–10 mm across. It attacks softwoods almost exclusively (pine roof trusses, pine floor joists), leaves a coarser sawdust that looks like couscous, and can hollow out a beam so completely that the outer shell is a millimetre thick and the load-bearing capacity is close to zero. If a peritación mentions Hylotrupes or carcoma grande on a pine roof structure, that is a structural finding, not a cosmetic one. Whole roofs have failed on this.

How to spot woodworm on a viewing. Bring a torch. Look at every exposed beam, joist and door frame at close range, especially where the beam meets the wall (the damp end) and where it meets the exterior (the eaves end). Look for:

• Small round or oval exit holes in the surface of the wood.
• Small piles of fine, pale sawdust on beams, on shelves, on the floor directly below a beam, on top of skirting boards. Fresh serrín is pale cream; old is grey.
• Squeaks and give. A live beam with heavy internal tunnelling flexes audibly when you press hard on the underside. A dead one thuds.
• Frass on the ground floor in a house that has been closed up for the winter is a giveaway — nothing else deposits pale sawdust from the ceiling onto a clean tile.

How to know if it is active. Old exit holes with dust inside them are historic. Fresh exit holes with pale, sharp edges and serrín on the floor beneath them are active. If in doubt, wipe a beam clean with a rag, mark the date, and look again in a month. Any new serrín is a live infestation.

What treatment costs in 2026 euros. For a village house with, say, 40–60 linear metres of exposed beam and joist:

• Localised chemical treatment (permethrin- or boron-based, injected into holes drilled every 30 cm along each affected beam, then sprayed on the surface): €35–60 per linear metre of beam, plus a call-out. A typical 40–60 m job is €1,800–3,500, guaranteed for 10 years by the treating company.
• Anoxic tent treatment for a specific piece of furniture or a small area (the beam is wrapped in a nitrogen-flushed bag for two to three weeks, killing every stage of the life cycle without any chemicals): €800–2,000 for a single-room extent. Rarely used on a whole house.
• Microwave or heat treatment (rising as of 2024–2026 as it kills without chemicals and is safe for occupied houses): €60–110 per linear metre. Faster, cleaner, no residual smell, but the company kit is expensive so it is only available in the big provincial capitals.
• Full beam or joist replacement, for a Hylotrupes-hollowed structural member: €450–900 per metre including shoring, replacement, and lime-mortar make-good. This is the number that separates a bargain from a project.

The single most important cost variable is how many beams are structural and how many are decorative. A ceiling that looks all-beamed often has, above the visible chestnut, a second modern reinforced-concrete slab doing the actual work — a common 1970s intervention in Andalusia and the Levante. If so, the carcoma is a cosmetic problem you can treat for a few thousand euros. If not, it is the roof over your head.

Termites (termitas) — the reason a house can look fine and be gone

Spain has two termite species that matter for buildings:

Mediterranean subterranean termite (Reticulitermes lucifugus). This is the one you meet in 97% of Spanish termite cases. Present across the entire peninsula, densest in Andalusia, Extremadura, Castilla-La Mancha, the Levante and inland Catalonia; also, increasingly and worryingly, along the wetter Atlantic north (the range has been creeping north with climate warming since about 2005). Lives underground in a central colony of up to a million individuals, sends worker tunnels up into the wood of your house through the foundations, and eats it from the inside — but never breaks the outer surface. From the outside, a termite-eaten beam looks perfect. On the inside, it is a shell. The only visible sign, most of the year, is the swarm in late spring: on a warm afternoon in April or May, alates (winged reproductives) emerge from the colony, fly in a small cloud, drop their wings, and vanish. Discarded translucent wings on a windowsill in a house you are viewing in May are a five-alarm warning.

West Indian drywood termite (Cryptotermes brevis). Rare on the peninsula, present in the Canary Islands (particularly Tenerife and Gran Canaria) and locally in some Andalusian coastal towns. Does not need soil contact — the whole colony lives inside a single piece of wood. Leaves small piles of hard, gritty, hexagonal-shaped droppings (heces, sometimes described as looking like coffee grounds) on the floor under the infested wood. Highly destructive, but detectable if you know the droppings.

How to spot termites on a viewing. Termites are stealthier than carcoma. The signs are subtler:

• Mud tubes (Spanish: cordones or galerías de barro). Thin, pencil-diameter tubes of grey-brown mud running up a wall, across a beam, along a floor, between the ground and a piece of timber. This is how Reticulitermes travels between its underground colony and your ceiling. Any mud tube inside a Spanish house is termites, full stop. Do not tap it, poke it, or dislodge it — the seller will just paint the wall — but photograph it.
• Beams that sound hollow when tapped, but show no exit holes. This is the classic Reticulitermes signature: eaten inside, intact outside. A screwdriver pushed firmly into the underside of a suspect beam will punch through the shell with no resistance if the beam is termite-hollowed.
• Wings on windowsills, in cobwebs, or on the floor in April, May or June. About 6–10 mm long, translucent, in pairs. Termites drop them all at once after swarming.
• Doors, shutters and skirting boards that have "sagged" — a door that was fine last year and no longer closes because the frame has been eaten from within.
• Small brown droppings piled below suspect wood, in the Canaries or on the coast: Cryptotermes brevis.

Where they are worst. Any old cortijo, masía or village house that has stood empty for over five years in Andalusia, Extremadura, Murcia, Valencia, southern Aragón or inland Catalonia should be assumed to have some level of Reticulitermes presence until a specialist certifies otherwise. Newer builds are much less at risk because Spanish building regulations since the CTE (Código Técnico de la Edificación, 2006) require anti-termite barriers in high-risk zones.

Treatment in 2026 euros. Two approaches:

• Chemical barrier treatment (injecting a soil-treatment insecticide such as fipronil around the entire perimeter of the house and under any suspect internal wall, plus treating affected timber directly). The traditional method. Costs €12–22 per m² of floor area of the treated house, so €1,500–3,500 for a village house, up to €5,000–8,000 for a large cortijo with outbuildings. Guaranteed for 5–10 years.
• Bait systems (in-ground cellulose-and-hormone bait stations placed every 3–5 m around the property, colonies eat the bait and pass it back to the colony, whole colony dies over 3–9 months). Slower but the modern standard, especially for houses with archaeological or listed sensitivity where you cannot drill or inject. Costs €2,500–5,000 for a village house, with an ongoing annual monitoring contract of €250–500 per year.
• Replacement of eaten structural timber: as with Hylotrupes, €450–900 per metre of joist, plus the shoring and make-good.

The number to remember is that a mature Reticulitermes colony does not go away without treatment. Ignoring it for three years costs another beam. Ignoring it for ten costs the whole roof structure.

Damp (humedades) — the three species foreign buyers meet, and only one is cheap

The Spanish word humedades covers everything the English word "damp" does, plus a couple more. On a peritación or a builder's quote you will see it broken into three:

1. Humedad por capilaridad — rising damp. Groundwater climbing the walls from the foundation, wicking up through stone or tapial by capillary action. The single most common damp problem in Spanish village houses because almost no pre-1980 rural build has a damp-proof course. Visible as a horizontal tide-mark at 30–100 cm above floor level on interior walls, with blown paintwork, powdery efflorescence (eflorescencias salinas, whitish salt crystals), a musty smell, and sometimes buckled skirting boards or lifted floor tiles. Worst on north-facing walls, worst in autumn and spring, invisible in August. This is the expensive one. True treatment requires either a chemical damp-proof course (drilling holes at floor level and injecting a silane- or siloxane-based cream), an electro-osmotic system, or the traditional Spanish trick of digging out the perimeter to expose and re-render the foundation. Costs:

• Chemical DPC injection: €90–160 per linear metre of wall. A typical village house with 30–40 m of affected perimeter is €3,000–6,500.
• Electro-osmotic system: €3,500–7,000 for a whole house, plus annual power.
• Perimeter drainage plus re-render: €10,000–25,000 depending on ground and access. This is the "proper" fix but genuinely expensive.
• "Doing nothing and re-painting every three years with a breathable lime paint": what most rural Spanish owners actually do, and what quietly keeps the house standing but keeps the plasterboard permanently blown at foot level.

2. Humedad por filtración — penetrating damp. Water getting in from outside the wall or roof: a cracked roof tile, a blocked gutter, a broken downpipe, a rendered exterior with a hairline fissure, a badly sealed terrace above a living room. Shows as an irregular, expanding stain at the top of a wall, or on a ceiling, often circular, often below a suspect roof feature. Easier to diagnose than rising damp because the source is usually directly above. Costs:

• Locating and fixing the roof or exterior source: €300–1,500 for a straightforward roof-tile or gutter repair; €3,000–8,000 for a full re-render of a rain-facing wall.
• Interior make-good (stripping blown plaster, drying, re-plastering, painting): €40–70 per m².

3. Humedad por condensación — condensation damp. The one that pretends to be one of the other two. Water condensing out of the interior air onto cold surfaces (corners, north-facing walls behind wardrobes, single-glazed window reveals). Shows as black mould in the coldest corners, especially bathrooms and bedrooms with a wardrobe against an outside wall. Massively underdiagnosed in Spain because the same rural houses that have rising damp also have wildly variable ventilation and no insulation. Costs:

• Improving ventilation (installing extractor fans in bathroom and kitchen, opening trickle vents, cleaning existing ones): €300–900.
• Insulating the cold internal walls or ceiling: €25–60 per m².
• Double-glazing to fix window-reveal condensation: €500–900 per opening for standard aluminium, more for wooden reveals in a listed frame.

The trap on damp is that all three can be present in the same wall, and a cheap contractor will diagnose whichever they know how to fix. A proper peritación with a hygrometer, an inspection of the exterior of the same wall, and a Karsten-tube pressure test if warranted, is the only way to know what you are actually paying to solve.

Where in Spain each problem is worst

A rough map, useful for calibrating your due diligence:

Region	Worst risk	Notes
Andalusia (inland)	Termites and rising damp	Old cortijos in Málaga, Sevilla, Córdoba, Jaén provinces are termite epicentres.
Andalusia (coastal)	Rising damp and salt penetration	Chiringuito-adjacent flats: salt-laden air corrodes everything.
Extremadura	Termites, woodworm	Old rural stock, mild winters, ideal for both.
Castilla-La Mancha	Rising damp, woodworm	Rammed-earth (tapial) walls wick beautifully.
Castilla y León	Woodworm and condensation	Cold winters, poor ventilation, but drier subsoil.
Valencia / Murcia / Costa Blanca	Termites, salt, rising damp	Old huerta farmhouses and older coastal blocks are termite-prone.
Catalonia (inland)	Termites, damp in masías	Vallès and Empordà masías often show all three.
Catalonia (Barcelona)	Rising damp in fincas antiguas	Pre-1940 Eixample blocks, especially ground floors and entresuelos.
Balearics	Woodworm, salt, condensation	Termites less common; salt corrosion of iron beams severe.
Basque Country / Cantabria / Asturias	Damp of all three types, some woodworm	La España verde is a damp zone; termites historically absent, arriving now.
Galicia	Damp, damp, and more damp	Rainfall does the rest. Termite arrival is recent but real.
Canary Islands	Cryptotermes (drywood termites), damp on north-facing walls	The one region with the second termite species.
Aragón / La Rioja	Woodworm and condensation	Very cold winter interiors on stone walls: heavy condensation.
Madrid	Rising damp in old central fincas	Solid brick pre-1940 blocks with no DPC. Modern peripheral stock: none of it.

Two nuances the table hides. First, rising damp is a hazard of solid-wall pre-1980 construction anywhere in Spain — the region matters less than the age and construction of the specific building. Second, termites are arriving in northern Spain for the first time in recorded history. If you are buying in Asturias or Cantabria, do not assume the historic absence protects you; ask the perito explicitly.

The 40-minute viewing checklist

Print this. Take it. Ignore the idealista-glossy furniture.

Outside, first.

1. Walk the full perimeter. Note ground level relative to the interior floor — every 10 cm the ground has risen against the wall over the centuries is a 10 cm capillarity risk.
2. Look for cracked, missing or slipped roof tiles, blocked gutters, broken downpipes, missing lead flashings around chimneys.
3. Check where the downpipes discharge — into a drain, or straight into the ground against the wall? The second is a factory for rising damp.
4. Look at the render on the north and west walls (wettest exposure) for hairline cracks, blown patches, or a dark tide-line at ground level.
5. Note any mud tubes on external walls, particularly under the eaves, on garden walls, or against fences.

Inside, systematically.

6. As you enter, breathe deeply. Damp has a specific musty smell. Fresh paint plus a burning candle is what an agent uses to hide it — if either is present without reason, ask why.
7. In every room, look at the skirting boards and lower 1 m of every wall, especially on the ground floor, on north-facing walls, and against exterior walls. Blown paint, salt bloom, buckled skirting = rising damp. Push a skirting board with your foot: soft = wet.
8. Look at ceilings and the top corners of walls for circular or irregular brown stains: penetrating damp.
9. Look at corners, behind furniture pulled out slightly, and around windows for black mould: condensation damp.
10. In rooms with exposed beams, stand under each beam with your torch on. Look for exit holes; look for sawdust piles on the floor or on shelves.
11. Tap every accessible beam with the handle of a screwdriver. A live sound beam thuds solidly. A termite-eaten beam sounds hollow. A Hylotrupes-eaten beam crunches.
12. Look at windowsills in April, May and June for wings. Two-week-old wings will still be recognisable months later; look also on top of picture frames and in cobwebs.
13. In the Canaries or on the Andalusian coast, look on the floor directly under exposed timber for small piles of hexagonal-shaped droppings.
14. Open every wardrobe pushed against an external wall — the back panel is the honesty test for both damp and mould.
15. Ask to see the electrical fuse box. If it has been replaced in the last five years, ask why. A recent full rewire is often the tell that a house had water somewhere it should not have been.

Ask, out loud.

16. Ask if the house has ever been treated for carcoma or termitas, and if there is a certificado de tratamiento with a guarantee. If yes, ask for the certificate and the treating company's name. Certificates transfer with the property.
17. Ask when the roof was last replaced or checked and by whom.
18. Ask if a peritación has ever been done and whether there is a report.
19. Ask why the previous owner is selling. "Their children live in Madrid" is normal. "They're moving to a house without stairs" is normal. "The roof gave them problems" is a red flag they may accidentally hand you.

The peritación — the report that turns the checklist into a number

The Spanish peritación or inspección técnica del inmueble is a full building survey by an arquitecto técnico or aparejador. It is not standard practice on Spanish resale purchases — the average Spanish buyer does not commission one — but for foreign buyers of any property over about 30 years old it is close to indispensable. Costs range from €350–700 for a flat, €700–1,500 for a village house and €1,500–3,500 for a cortijo or masía with outbuildings. This is meaningfully cheaper than what a comparable RICS survey costs in the UK, and infinitely cheaper than the finding it saves you from.

Two things to insist on before you hire a perito:

• A named check for carcoma, termitas and humedades in the scope of the report, not just a general structural inspection. The default peritación is a walk-through of walls, roof, and installations; some peritos will note wood-boring insects and damp only if they are visually obvious. Ask explicitly for a hygrometer measurement on every wall, a probe check of every accessible timber, and an inspection for mud tubes.
• A photographic report with the specific concerns listed on the summary page. Buried in a 40-page PDF, a two-line note about carcoma in the master bedroom beam is a note. On the summary page in bold, it is a negotiating instrument.

The two lines that decide the purchase are almost always in the first page of the summary and the last page (recommendations). If the perito says "se recomienda un tratamiento integral contra la carcoma antes de la ocupación" or "se aprecian indícios de humedad por capilaridad en muros de planta baja", then those are the sentences you show the seller's agent. Do it in writing, with the report attached, and ask for a price reduction equal to the specialist quote you have obtained since. Sellers in Spain do accept these reductions surprisingly often, because the survey's existence protects both sides — the seller can no longer plead ignorance, and every subsequent buyer who commissions their own peritación will see the same problem.

What home insurance covers, and the surprises

The standard Spanish seguro de hogar (home insurance) covers sudden and accidental water damage — a burst pipe, a washing machine overflow, a storm-driven roof leak. What it almost universally excludes:

• Damage caused by wood-boring insects of any kind. Termite damage, woodworm damage, everything. Not covered. Not by the standard policy, not by any cobertura ampliada we have seen. You are on your own.
• Rising damp and any other "pre-existing" damp condition. If the survey shows humedad por capilaridad, no insurer will subsequently pay to remediate it. Insurance covers events, not chronic conditions.
• Gradual leaks in a roof or terrace that were "visible or should have been visible" before the escalating damage occurred. Push a leak into the walls for two years without fixing it and your insurer will decline the eventual repair.

What is covered, and often generously, is the subsequent damage from a sudden event — if a storm rips off a section of roof and rain destroys a bedroom ceiling, the ceiling is covered even though the roof itself may not be. Read the condiciones generales line-by-line before completion; a decent broker will translate. Consider a specific seguro decenal style contract when you commission remediation for any of the three problems — almost all Spanish specialist companies offer a 10-year guarantee (garantía decenal) on their treatment. This is what covers you against reinfestation on their watch, not your insurance.

What to do in the first six months of ownership

Assume the house has all three problems until proven otherwise. Six moves that pay for themselves inside a year:

1. Book a proper peritación now if you skipped it at purchase. Yes, before completion is better. But before your first winter is still cheaper than after your first winter. Spanish humidity peaks between October and February; a survey done in November catches things a July survey never sees.
2. Instrument the house. A hygrometer (€15) in every room, a notebook with monthly readings, and a damp meter (€40–80) for pressing into skirting boards. Numbers are how you distinguish a real problem from paranoia. Interior air above 65% relative humidity for months at a time is a condensation-damp precursor.
3. Get quotes from at least two treatment companies for any confirmed carcoma or termitas infestation. Ask each for their guarantee terms in writing. The 10-year garantía is table-stakes; ask what triggers it (reinfestation, structural damage, both) and what documentation you need to preserve to claim.
4. Fix the roof and the gutters before you paint the walls. This is the single most common inversion of priorities. Water enters from the top and the bottom, always. Interior finishes are the last stage, not the first.
5. Ventilate. Open the windows across the house for 15 minutes a day, even in winter, especially in winter. Cross-ventilate the bedroom before you make the bed. Every €3 of heating you lose is €100 of condensation-damp remediation you don't pay later.
6. Write down what you were told. Ask the seller in writing for any treatment certificates, historic peritaciones, roof-work invoices, and the name of the local albañil they used. Get it in the acta before completion when possible. The paper trail is worth money at every subsequent stage of ownership and, one day, sale.

The bargain house that is not a bargain

The clearest test of whether a low-priced Spanish rural house is a bargain or a project is not the price per square metre. It is the ratio of asking price to the sum of a proper roof repair, a full termite-and-woodworm treatment, and a rising-damp intervention. If those three remedial numbers together approach or exceed the discount you are being offered against comparable stock in the same village, the "bargain" is a project priced as a bargain. Do the sum before arras, not after.

The corollary is that a house with a clean peritación, a treatment certificate under its 10-year guarantee, a recently re-tiled roof and a documented DPC intervention is worth materially more than the m² average suggests — because you inherit certainty, not a slow-motion audit. A foreign buyer who understands that pays the difference happily. A foreign buyer who doesn't pays it eventually, on a ladder, holding a screwdriver, with an albañil who is very sorry about the news.

Old Spanish houses are one of the great pleasures of European property ownership. Beams that were felled while Cervantes was alive, walls a metre thick, courtyards that a hundred cats and four generations of a family have already broken in for you. The three invisible enemies are the tax you pay for that pleasure. Understand them before you sign, and the tax is affordable. Miss them, and the house eats itself, slowly, and mostly at night.