Investigate moisture, ventilation and the pattern of recurrence.
All decorating problems
Moisture & stains · H&C advice
Mould & condensation marks
Dark spotting or recurring staining may develop in moisture-prone areas.
- Spotting around cold corners, window reveals or bathrooms.
- Condensation and marks returning after cleaning or decorating.
Understand before treating
What might cause it?
Similar-looking defects can have different causes. Assessment comes before product choice.
Excess humidity, inadequate ventilation, cold surfaces or water ingress can contribute. More than one cause may be present.
Preparation & next steps
How we approach it
Arrange suitable cleaning or remediation, following safety guidance and product instructions.
Only redecorate a suitable dry surface; discuss a coating suited to the room without treating paint as the cure.
Do not dry-brush or sand mould. Extensive or recurrent growth, vulnerable occupants or suspected hidden contamination need specialist advice. Check current product technical data, safety instructions and compatibility; this guide is not a site diagnosis or a guaranteed repair specification.
The right system for the surface
Product selection matters
A suitable primer or sealer may be part of the preparation, but it cannot replace fixing the cause. Zinsser is one of the brands we use; the exact product depends on the surface, defect and intended finish.
Zinsser UK product guidanceOriginal H&C guidance. We are not approved, accredited or endorsed by Zinsser.
Local decorating help
Let’s look at the problem properly.
Share your postcode, the affected surface and what you’ve noticed. Preparation and repairs are assessed before a quote is agreed.