Note
Damp and mould in Spanish homes: what to check
Quick answer
Damp comes from rain, the ground or condensation, and each has a different cure. The technical code limits foreseeable water or moisture from those three sources and requires ventilation. On a viewing, look at corners, low walls and window frames, and ask a surveyor to test before you commit.
Applies toBuyers viewing older homes, ground floors, cellars or homes that have stood empty.
On this page: 10 sections
§ 1Three sources
The technical building code, in its section on protection against moisture, says that the foreseeable risk of inappropriate presence of water or moisture inside buildings must be limited, and it names the sources: rain, run-off, the ground and condensation. The first two are about water getting in. The third is about the home producing moisture that lands on cold surfaces. Each needs a different cure. This page belongs to the chapter on more on energy and comfort.
§ 2What to look for
Check the corners of ceilings and the foot of the walls for stains, flaking paint, salt deposits or a musty smell. Look behind furniture and inside wardrobes on outer walls. Look at window frames for black spots and at bathrooms for failing seals. Check the roof from outside, the gutters and the downpipes, and the ground against the walls. A fresh coat of paint on one wall can hide a problem.
§ 3Ground floors and cellars
The code treats walls and floors in contact with the ground separately, and it sets waterproofing and drainage requirements depending on how much water is present and how permeable the ground is. Older homes were not built to this standard. Ask about drains, damp courses and past flooding, and read more on insulation on how insulation changes surface temperatures. Ask a surveyor to measure.
§ 4Condensation and ventilation
Condensation depends on the heat, the insulation and the ventilation. The code refers the checks of condensation to its energy-saving section, and it requires means to ventilate rooms so that the pollutants of normal use are removed. A home with no way to ventilate, such as sealed windows without trickle vents, will have condensation. A dehumidifier treats the symptom, not the cause. More on heating explains how heating affects it.
§ 5Empty homes
A home that is closed for months builds up moisture and mould. The section on owning and selling explains the risks of an empty home and the routine of airing and checks. If the home stood empty for long, ask how long and who looked after it.
§ 6Ask for a survey
Ask a qualified surveyor to inspect and to give a written report, with a cost for each remedy. A pre-contract finding can be used in negotiation or as a reason to walk away. A defect found after purchase is harder to claim, as the legal section on hidden defects explains. Include the findings in your lawyer’s file.
§ 7Remedies
Typical remedies are repairing leaks, improving drainage, waterproofing walls, adding ventilation, insulating cold surfaces and heating steadily. Costs differ widely, and we found no official price list, so ask for quotes.
§ 8Health
Mould is more than a cosmetic matter, but we did not read official health guidance. If someone in the household has asthma or an allergy, ask a doctor how much it matters before you buy.
§ 9What we could not verify
We read the code’s summary of the sections on moisture and ventilation and not the technical detail of each solution.
§ 10More on this topic
More on solar panels explains the rules for installing solar panels on a Spanish home and more on solar subsidies and tax breaks explains the help available for solar and energy works and what we could not verify.
FAQRelated questions
How do I tell damp from condensation?
Condensation shows on cold surfaces such as window frames and corners and eases with ventilation and heat. Rising or penetrating damp leaves stains and salts low on walls or near leaks, and does not clear with airing. A surveyor can confirm.
Is mould dangerous?
It can irritate the airways and damage finishes, and it signals a moisture problem that needs a cause fixed. We did not read official health guidance on this, so ask a doctor about specific health concerns.
Does the code apply to my old house?
The code’s moisture section is written for buildings within its scope, and the text we read does not say directly how it applies to existing ones. It does mention rehabilitation. Use it as the standard a surveyor will refer to.
Sources
- Ministerio de Vivienda y Agenda Urbana: Documento Básico HS Salubridad (technical building code) (official source, opens in a new window), HS 1 moisture protection and HS 3 air qualityLast checked 18 October 2026
General information only. This is not legal, tax or financial advice. Check your own situation with a qualified adviser.