Common Signs of Damp: How to Spot the Warning Signs in Your Home

Damp is one of the most common problems faced by homeowners in the UK — and it’s also one of the easiest to overlook. What starts as a faint musty smell or a small patch of peeling paint can quickly turn into a bigger issue, leading to structural damage, health concerns, and costly repairs.

The good news is that if you know what to look for, you can often catch damp early and deal with it before it spreads. In this guide, we’ll walk you through the most common signs of damp and what they mean for your home.

1. Musty Smells — The First Red Flag

One of the earliest and most common indicators of damp is a persistent musty or earthy smell. Even if you can’t see visible signs yet, your nose can often detect the problem first.

This odour usually occurs when moisture becomes trapped in walls, plaster, or flooring — creating the ideal environment for mould spores and bacteria to thrive. If you notice a damp smell that doesn’t go away after cleaning or airing the room, it’s worth investigating further.

🟢 Pro tip: Pay close attention to basements, under-stairs cupboards, and behind furniture placed against external walls — these areas often hide the source of the problem.

2. Peeling Wallpaper or Bubbling Paint

Damp doesn’t always show up as obvious water patches. Sometimes it reveals itself through cosmetic damage, such as peeling wallpaper, blistering paint, or bubbling plaster.

This happens when moisture inside the wall pushes through to the surface, causing adhesives and finishes to fail. You might also notice staining or tide marks underneath the affected area — a clear sign that water is travelling through the plaster.

🟢 Pro tip: If the wallpaper is peeling mainly near skirting boards, it could be a sign of rising damp, where groundwater is moving up through the walls.

3. Black Mould Growth

Black mould is one of the most visible and concerning symptoms of damp — and it should never be ignored. It often appears as dark or greenish-black spots on walls, ceilings, or around window frames.

This type of mould thrives in humid, poorly ventilated areas such as bathrooms, kitchens, and bedrooms. While small patches might be cleaned temporarily, if the root cause of the damp isn’t addressed, the mould will always come back.

Aside from being unsightly, black mould can also cause serious health problems, including allergies, breathing difficulties, and aggravated asthma.

🟢 Pro tip: If mould returns soon after cleaning, it’s a sign that you have a deeper damp or condensation problem that needs professional attention.

4. Salt Deposits (Efflorescence)

If you’ve noticed white, powdery marks forming on your internal walls or brickwork, you’re likely seeing salt efflorescence — another telltale sign of damp.

When water moves through masonry or plaster, it carries soluble salts to the surface. As the moisture evaporates, the salts crystallise and leave behind a powdery residue.

While this might not cause direct damage, it’s a strong indicator that moisture is actively passing through your walls — often due to penetrating or rising damp.

🟢 Pro tip: Simply cleaning away the salt won’t solve the issue. You’ll need to identify and eliminate the source of moisture to stop it reappearing.

5. Damp or Discoloured Patches

Damp often causes patches of discolouration on walls, ceilings, or floors. These may appear darker than the surrounding area and can feel cold or wet to the touch.

• Patches near ceilings could indicate roof leaks or penetrating damp.

• Patches near floors often point to rising damp or issues with the damp-proof course.

If left untreated, these patches can lead to flaking plaster, crumbling brickwork, and long-term structural issues.

6. Condensation and Water Droplets

Excess condensation — particularly on windows, mirrors, or cold walls — is another common sign that moisture levels in your home are too high.

While condensation itself isn’t the same as rising or penetrating damp, it can trigger secondary problems like black mould, wood rot, and musty odours if not managed properly.

🟢 Pro tip: Improving ventilation with extractor fans or trickle vents can help reduce condensation — but if it persists, it could be a sign of underlying damp.

When to Call in the Experts

If you’re noticing any of these warning signs, don’t ignore them. Damp will not go away on its own — and delaying treatment only increases repair costs and potential health risks.

At Acorn Damp Proofing, we provide detailed surveys to identify the exact cause of damp in your home — whether it’s rising damp, penetrating damp, or condensation issues. Our treatments are tailored to your property and backed by a 10-year guarantee, giving you peace of mind that the problem won’t return.