Mould keeps coming back after cleaning | Homecode

What is known — and what is not

What the recurrence may mean

• Mould returns in the same external corner during cold weather and is accompanied by window condensation. Cold-surface condensation, heating and ventilation deserve assessment, but this pattern does not prove which condition is responsible. [1]
• The cleaned area becomes wet or grows again after rain. Penetrating water should be investigated before another surface treatment is considered. [1]
• Recurrence follows use of a nearby bath, shower, appliance or heating system. A plumbing or service leak becomes more plausible, but the visible mould may be away from the leak itself. [1]
• Growth returns quickly across several areas or a musty smell persists behind finishes or furniture. Concealed affected material or several moisture sources may need a planned inspection. [1]

What you can check without disturbing it

• Photograph each recurrence from the same position before further cleaning and record the date, approximate area and room. [1]
• Keep the previous survey, cleaning, repair and decorating records together and note how long the surface stayed clear. [1]
• Log rain, water use, heating, window condensation and the normal observed operation of accessible existing vents without changing controls or dismantling anything. [1]
• Tenants should report the recurrence and any health concern in writing rather than treating each return as a new cleaning task. [1]

When to stop and escalate

• Do not treat another mould wash, bleach application or coat of paint as proof that the moisture source has been resolved. [1]
• Do not strip wallpaper, lift fitted flooring, open a cavity or move contaminated porous material merely to find hidden growth. [1]
• Stop relying on surface cleaning when mould is extensive, spreading, repeatedly returns or may be affecting an occupant's health. [1]

Who to contact and what to ask for

• Follow the professional route in the safety block when mould returns, is extensive, may be concealed or is associated with health concerns. [1]
• Ask the assessor to revisit the original cause, inspect internal and external moisture routes, state uncertainties and explain why the proposed work should prevent recurrence. [1]
• After diagnosis, obtain comparable itemised quotes for source repair, safe mould work, drying, reinstatement and a follow-up check.

Sale and letting impact

• Repeated mould or fresh local paint can prompt buyer and surveyor questions. Keep the diagnosis, recurrence record, repair specification and follow-up evidence rather than presenting decoration as resolution. [2]
• In England, a landlord should investigate recurring damp and mould, address underlying causes and consider occupant vulnerability rather than relying on repeated surface cleaning. [1]

Mould cleanup safety boundary

• GOV.UK says simply removing surface mould will not prevent it returning. Identify and tackle the moisture source first. Occupier cleaning is not a substitute for that assessment. [1]
• Photograph the affected area before cleaning. GOV.UK says mould should not be left for long periods, but the priority is still to protect health and fix the cause. [1]
• Most people could reasonably remove condensation and very small amounts of mould with an appropriate mould and mildew cleaner. Larger areas should only be addressed by qualified professionals. Official UK guidance does not publish a numeric area threshold. [1]
• Regardless of extent, wear a mask, gloves and goggles. Shut doors to other rooms and leave windows open during and after cleaning. Prefer a mould and mildew product to bleach. Wash or dispose of cloths and protective equipment afterwards. [1]
• Do not dry-brush, sand, scrape or vacuum mould. Disturbing hidden mould behind wallpaper, under carpets or inside voids can release a significant number of spores; seek a trained professional if you have concerns. [1]
• People with lung or heart disease, a weakened immune system, children and other groups listed in the GOV.UK guidance are at greater health risk. Anyone concerned about symptoms should consult a healthcare professional. Property action should not wait for medical evidence. [1]