Damp and mould? Here’s what’s causing it

Damp and mould are among the most common — and most misdiagnosed — problems in UK homes. Getting the type of damp right matters, because the fix (and the cost) is completely different. Here’s how to tell them apart, what you can tackle yourself, and when to bring in a professional — plus how to make sure any quote is fair.

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The three main types of damp

Condensation — by far the most common. Caused by moisture in the air (cooking, showering, drying clothes) hitting cold surfaces. Shows as black mould in corners, around windows, and behind furniture.
Penetrating damp — water getting in from outside through a fault: damaged render, leaking gutters, cracked pointing, or roof issues. Often a damp patch that worsens after rain.
Rising damp — much rarer than people think. Moisture rising from the ground where a damp-proof course has failed. Usually a tide-mark up to about a metre on ground-floor walls.

What you can do yourself

If it’s condensation (the most likely cause), you can often improve it yourself: ventilate when cooking and showering, use extractor fans, avoid drying washing indoors, and keep a little background heat on. Clean small areas of mould with an appropriate mould remover. Better ventilation fixes a surprising amount.

If mould keeps returning over a large area, or you have a vulnerable person in the home, get it looked at — persistent mould can affect health.

When to call a professional

Damp patches that worsen after rain (likely penetrating damp — needs the external fault fixed).
A tide-mark rising up a ground-floor wall (possible rising damp).
Mould that keeps returning despite good ventilation.
Any damp linked to a leak, roof, or guttering problem.

Be cautious here: some firms push expensive chemical damp-proofing for what is actually condensation or a simple leak. Get the cause diagnosed properly — ideally an independent damp surveyor — and always get two or three quotes for any significant work. Then check the quote is fair before committing.

Frequently asked questions

How do I know if it is condensation or rising damp?

Condensation shows as black mould on cold surfaces, in corners and around windows, and is by far the most common. Rising damp is much rarer and shows as a tide-mark rising up to about a metre on ground-floor walls. Penetrating damp appears as patches that worsen after rain.

Can I get rid of mould myself?

If it is condensation-related and a small area, yes — improve ventilation, reduce indoor moisture, and clean it with a suitable mould remover. If it keeps returning, covers a large area, or is linked to a leak, get a professional to diagnose the underlying cause.

How much does damp treatment cost?

It varies hugely depending on the type and cause — from minor ventilation fixes to major work. Because some firms over-sell chemical damp-proofing, get two or three quotes and use our free quote checker to see whether a price is in the normal range.

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