Serving Berkshire & Surrey 50+ Yrs Combined Experience
01784 918 841 info@above-water.co.uk
Above Water
ABOVE WATER
Damp Proofing Specialists
Navigation
Book a Survey
Damp Guide

Black Mould on Walls: Causes and How to Stop It Coming Back

Black mould is almost always a sign of too much moisture in the air settling on cold surfaces. Cleaning it off is only half the job. Unless the cause is fixed, it will come back.

Why black mould grows

Mould needs moisture to grow. In most homes that moisture comes from condensation: everyday activities such as cooking, showering and drying clothes indoors put water into the air, and it condenses on the coldest surfaces, such as outside walls, corners, window reveals and the space behind wardrobes.

Leaks, penetrating damp and poor ventilation in bathrooms and kitchens make it worse.

Is black mould harmful?

The NHS advises that damp and mould can cause or worsen breathing problems, allergies and asthma, and that babies, older people and anyone with a respiratory condition or weakened immune system are more at risk. It is worth dealing with promptly.

How to remove it safely

  • Wear gloves, a mask and eye protection and open a window
  • Use a mould removal product designed for the job and follow the instructions
  • Wipe rather than brush, so spores are not spread into the air
  • Only tackle small areas yourself. Large or recurring mould needs the cause investigating

How to stop it coming back

  • Use extractor fans when cooking and showering, and leave them running for a while afterwards
  • Keep trickle vents on windows open and avoid drying clothes on radiators
  • Keep rooms at a steady, moderate temperature rather than heating them in short bursts
  • Leave a small gap between furniture and outside walls
  • Where condensation is persistent, a whole-house ventilation system such as positive input ventilation (PIV) can help

Common questions

Why does mould come back after I clean it?

Because the moisture that feeds it is still there. Cleaning removes the mould you can see, but unless condensation or the leak behind it is fixed, it will grow back.

Does anti-mould paint work?

It can slow mould down on the surface, but it does not fix the cause. Use it after the moisture problem has been dealt with, not instead of fixing it.

Could my mould be caused by rising damp?

Rising damp usually shows as a tide mark and salts low on ground floor walls rather than black mould. Mould high on walls, on ceilings or upstairs is almost always condensation.