This family home in Southampton (SO15) had black mould returning in almost every room. It ran along the line where the walls meet the ceiling, gathered around the bay window and spread across the bathroom ceiling. The owners had cleaned it off many times. Within weeks it was always back.
That pattern is the clue. Mould that keeps coming back after cleaning is nearly always a moisture problem, not a cleaning problem. Here is how we found the cause and fixed it in six days.
What we found on the survey
Our surveyor checked every room with moisture and humidity readings. The walls themselves were not wet from the outside, and there was no sign of rising or penetrating damp. Instead, the mould sat exactly where you would expect condensation to form: on the coldest surfaces, in corners and at ceiling junctions where air barely moves.
Everyday living puts a lot of water into the air. Cooking, showers, drying clothes and even breathing all add moisture. In this house, that moist air had nowhere to go. The bathroom had a small, tired extractor fan that was not moving enough air, and the rest of the house had no steady ventilation at all. When the warm, wet air touched the cold edges of the rooms, it turned back into water, and mould grew on it.
What we did
We treated the cause and the symptoms together, because one without the other does not last.
- Mould removal. Every affected wall and ceiling was treated with an acetic-acid solution. This kills the surface growth and cleans it back, rather than just bleaching the stain so it looks clean.
- Anti-condensation coating. We then applied a specialist anti-condensation treatment to the affected walls and ceilings. It makes the surface a little warmer to the touch, so condensation is far less likely to form there.
- New bathroom extractor fan. The old fan came out and a properly sized, high-quality extractor went in, so steam from showers is removed at the source.
- Positive Input Ventilation (PIV). We fitted a PIV unit in the loft. It gently pushes filtered fresh air into the house through a ceiling outlet on the landing. That steady flow of drier air pushes moist air out and keeps humidity down in every room, all day, without the owners having to think about it.
Our team protected the rooms throughout and left the house clean at the end of each day. The whole job took six working days.
The result
The house now has controlled, continuous ventilation and a bathroom fan that actually clears the steam. The treated rooms have been redecorated, and with humidity under control the mould has no conditions to come back in. You can feel the difference as soon as you walk in: the air is fresher and the musty smell has gone.
Why this approach works
Many mould treatments fail because they stop at cleaning. If the air in the house is still too wet, the mould simply grows back. Fixing it for good means three things: remove the mould properly, make the cold surfaces less attractive to condensation, and get the moisture out of the air. That is what our black mould removal and prevention work is built around, alongside our condensation and moisture control service.
Common questions
Will a PIV unit make my house cold?
No. Most units temper the incoming air, and the airflow is gentle. Most homeowners notice fresher air, not a draught.
Can I just buy anti-mould paint?
It can help on the surface, but it will not stop condensation forming. Without better ventilation, mould usually returns.
Do you cover the rest of Southampton?
Yes. Our Southampton team covers the whole city and the surrounding area.
Seeing the same signs at home?
Book a complimentary In-Depth Survey and one of our ISSE-accredited surveyors will find the cause, show you the readings and give you a written, itemised quote. Call 01202 287503 or request a callback. We'll phone you back within 5 minutes.