Dampness in buildings is one of the most frequent causes of litigation in Spain. Neighbors sue neighbors, owners sue developers, communities sue construction companies. But there is a serious problem:most expert reports confuse the real cause of humidity.
Attributing a stain on the wall to “leaks from the upstairs neighbor” without technical evidence is not only a diagnostic error: it is a legal risk. Because in court, if you do not prove the origin withmeasurable evidence and applicable regulations, your claim (or your defense) will fall apart.
A rigorous judicial expert opinion is not based on assumptions. It is based ondata, tests and regulations. And the first thing you need to do is answer a key question: what type of humidity is it?
The 3 Types of Humidity (and Why Confusing Them Ruins a Trial)
Not all humidity is the same. Confusing them leads to blaming the wrong person. Here the essential technical differences:
| Humidity type | Main cause | Typical symptoms | Key regulations |
|---|---|---|---|
| Due to condensation | Lack of ventilation + thermal bridges | Mold in top corners, foggy windows, no stains on baseboards | CTE DB-HE (energy saving), DB-HS (healthiness) |
| By capillarity | Rise of watergroundby pores of the material | Stains on skirting boards (up to 1–1.5 m), white salts (efflorescence) | CTE DB-HS3: requires a physical barrier against humidity |
| By filtration | Outside water entering through cracks, joints or covers | Localized stains after rain, drips, chips | CTE DB-HS3, work conditions specifications |
A judicial expert must differentiate these origins withobjective tests, not with “it seems that…”.
Technical methodology for a valid judicial diagnosis
An expert reporton humidity must include at least:
- Infrared thermography: detects thermal differences associated with humidity (water cools the surface).
- Moisture content measurement: with resistance or capacitance hygrometers, in depth and surface.
- Salt analysis: the presence of nitrates indicates capillarity; chlorides, marine filtration; sulphates, industrial pollution.
- Review of construction plans: Was there a moisture barrier? Is the expansion joint well executed?
- Leakage tests(if safe): controlled simulation of rain to verify leaks.
Without these elements, the report lacks technical soundness and will be easily challenged.
Practical case: “Leaks in the roof… the fault of the neighbor upstairs?”
(Real case, anonymized data)
Situation: An attic owner sued the neighbor on the upper floor for “leaks in the roof caused by his terrace.”
Initial report (incorrect): “the humidity comes from the neighbor's terrace due to poor sealing of the pavement.”
Rigorous technical diagnosis:
- Thermography: showed humidity at the junction between the community roof and parapet, not under the private terrace.
- Controlled water test: when spraying only the neighbor's terrace, no moisture appeared. When spraying the deck gasket, yes.
- Plans: The joint lacked primer and sealant conforming to DB-HS3.
conclusion: the origin was not the private terrace, but a defect in thecommunity cover, responsibility of the promoter.
Result: The judge dismissed the lawsuit against the neighbor and shifted responsibility to the community (against the original builder).
Common errors in expert reports on humidity
- Say “it's filtration” without ruling out condensation or capillarity.
- Do not measure actual moisture content (just look at spots).
- Ignore the hygrothermal behavior of the building (orientation, insulation, ventilation).
- Do not cite the applicable regulations (DB-HS3 has been mandatory since 2006).
These errors are not only technical: they have direct legal consequences.
What should a valid expert report on damp include?
- Identification of thetype of humidity(with evidence).
- Exact location oforigin(with photos, bounded plans).
- Non-compliant regulations (if applicable): CTE, UNE, specifications.
- Clear causal relationship between the defect and the observed damage.
- Firma del perito y acreditación de competencia técnica.
conclusion
En litigios por humedades, el verdadero riesgo no es el agua: es culpar al responsable equivocado por un diagnóstico superficial. Un peritaje judicial riguroso no opina: mide, analiza, compara y concluye con base en la normativa y la física del edificio.
¿Tienes un litigio por humedades y necesitas un informe pericial basado en pruebas técnicas, no en suposiciones?
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