Black mould on ceiling

Black Mould on the Ceiling

Common in bathrooms and kitchens — almost always caused by condensation, not a leak.

OxfordshireDamp · Remedy · Restore

Field note

Category: Ceiling symptoms
Likely cause: Condensation
Guarantee: 10-year written

CSRT-accredited survey

Schematic · Plate 09

AP/DAMP

Common in bathrooms and kitchens — almost always caused by condensation, not a leak.

The cause

What causes it

Black mould patches on a ceiling — particularly in bathrooms, kitchens, and around vents — are almost always caused by condensation rather than a roof leak. Steamy rooms produce large volumes of warm, moist air that rises and condenses on the cooler ceiling surface, especially over an unheated loft. Without effective extraction, the air stays humid for hours after a bath or cooking session, giving mould spores ideal conditions to germinate. Properties with poor loft insulation suffer worst, since the ceiling itself runs colder than the rest of the room.

Presentation

What to look for

The mould typically appears as small clusters of black or dark green spots, growing into larger patches around extractor grilles, light fittings, and the perimeter of the ceiling. You may see it most clearly in the morning while the surface is still cool. Bath panels, tile grout, and the upper corners of shower enclosures often show similar growth. Wiping it away with bleach removes the colour but the mould returns within weeks if the underlying humidity is not addressed.

Why it matters

If it is left alone

Mould releases spores into the air you breathe, and bathrooms and kitchens — the rooms it favours — are also where you spend time at close quarters with the affected surface. The Housing Health and Safety Rating System treats mould as a Category 1 hazard in serious cases. Beyond health, recurring mould slowly stains and degrades paint, plaster, and silicone seals, eventually requiring full redecoration. Tackling the cause is straightforward, and once done usually keeps the room clear permanently.

The remedy

How we treat it

The reliable fix is to reduce humidity at source rather than just clean the visible mould. We assess the existing extraction in the room, replace under-sized or failing fans with humidistat-controlled units that run until the air is dry, and ensure ducting actually vents outside rather than into the loft. Where loft insulation is uneven we recommend topping it up, since a warmer ceiling condenses far less moisture. The mould itself is treated with a fungicidal wash and the surface redecorated with a mould-resistant finish. Work carries a written guarantee.

Recommended treatment

Condensation Control

Every treatment begins with a CSRT-accredited on-site survey, is delivered to a written specification, and is backed by a 10-year guarantee against recurrence.

Written specification 10-year guarantee

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See the full scope of work, typical timeline, and survey findings.

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