mould in the house
How indoor mould gets going, what to do in practice, and when to stop. A building guide, not a medical one.
Updated 2026-09-01 · 10 min read
Indoor mould is an organism that finds water, time and a surface. Remove standing dampness and growth stops. Leave the water and every anti-mould product is cosmetic.
If the stain returns in the same place within weeks, the cause is still there. Returning to diagnosis is cheaper than a third tin.
It can lighten a surface stain. It does not change the climate that produced it. On porous materials the roots remain. Protect skin and airways; do not mix products.
If surface RH stays high, it is a delay. It belongs as a finish after cause and climate are corrected, not as the only move.
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10–25 €
Without a relative-humidity number, every tip is guesswork. A €10–25 hygrometer is the first useful purchase — before any dehumidifier.
When: Always, as the first diagnostic step.
Not when: It does not replace a moisture meter or a rising-damp survey.
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80–350 €
Useful if indoor air sits above ~60–65% and the cause is indoor vapour (showers, cooking, laundry), not a wall wet from below.
When: Measured high RH, window condensation, indoor drying, windowless bath.
Not when: Rising damp, leaks, stains that start at the skirting and climb.
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8–25 €
Existing mould has to be removed. Anti-mould paint alone, if moisture stays high, is a delay.
When: After you understand the cause, while RH is being lowered.
Not when: Large areas, strong odour, vulnerable occupants: consider a professional.
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UNI EN ISO 13788
Prestazione igrotermica dei componenti edilizi. Soglia convenzionale di rischio muffa: umidità relativa superficiale 80%.
Accessed 2026-09-01
WHO guidelines for indoor air quality: dampness and mould (2009)
Sintesi epidemiologica su umidità indoor e sintomi respiratori. Non è una linea guida clinica italiana.
Accessed 2026-09-01
Istituto Superiore di Sanità — qualità dell’aria indoor
Materiali ISS su inquinanti indoor. Le pagine operative vanno verificate sul sito ISS perché l’organizzazione dei dossier cambia.
Accessed 2026-09-01
Damp at home: diagnose it before you buy anything
A step-by-step way to tell condensation, indoor vapour, rising damp and leaks apart. What to measure, what to watch, when not to buy a dehumidifier.
Mould behind a wardrobe: dead corner, thermal bridge, or both
Why the gap between furniture and an external wall stays damp, and what to do before anti-mould paint.
Mould in a windowless bathroom: extractor before dehumidifier
Why a portable unit in the lounge will not fix black silicone, and how to spec an extractor with a humidistat.