Damp is one of the most common problems in UK homes, and one of the most misunderstood. It's not a single issue — it's a category of problems with very different causes and very different solutions. Treating the wrong type of damp wastes money and leaves the underlying problem untouched.

Type 1 — Rising Damp

Rising damp occurs when moisture from the ground travels upwards through the walls by capillary action. It is most common in older properties without a damp-proof course (DPC), or where the existing DPC has failed or been bridged.

How to recognise it:

• Damp patches low on walls, typically up to about 1 metre from the floor
• A tide mark or salt staining (efflorescence) on the wall surface
• Peeling wallpaper or paint near the skirting
• Skirting boards that are soft, rotting, or discoloured
• A musty smell at low level

What causes it:

• Absent or failed damp-proof course
• External ground levels raised above the DPC (e.g. new paving, flowerbeds against the wall)
• Bridging of the DPC by render, soil, or debris

How it's resolved:

A new chemical DPC is injected into the mortar course, and any salt-contaminated plaster is hacked off and replaced with a salt-resistant renovating plaster. External ground levels should be reduced where possible.

Rising damp is often misdiagnosed. Condensation and penetrating damp can look similar at low level. Always get a proper diagnosis before committing to expensive treatment.

Type 2 — Penetrating Damp

Penetrating damp is caused by water getting in through the fabric of the building — walls, roof, windows, or around pipes. Unlike rising damp, it can appear at any height and is often linked to a specific weather event or a specific defect that can be identified and fixed.

How to recognise it:

• Damp patches that appear or worsen after heavy rain
• Patches at specific locations — around window frames, chimneys, or where extensions meet the main building
• Staining on ceilings or walls directly below a roof or gutter
• Damp in cavity walls, often appearing in patches on the inner leaf

Common causes:

• Failed or missing pointing in brickwork
• Cracked or defective render
• Failed window or door seals and flashings
• Blocked or overflowing gutters and downpipes
• Defective flashings around chimneys, dormers, or roof abutments
• Cavity wall insulation that has become saturated or bridging the cavity

How it's resolved:

The source of the ingress must be identified and repaired before any internal work is done. Redecorating over penetrating damp without fixing the cause is always a waste of money. Once the source is dealt with, affected plaster and decoration can be replaced.

Type 3 — Condensation

Condensation is by far the most common form of damp in UK homes, and it's also the most frequently misdiagnosed as rising or penetrating damp. It occurs when warm, moist air comes into contact with cold surfaces and the moisture condenses out.

How to recognise it:

• Black mould growth on walls, ceilings, window reveals, and in corners
• Streaming windows in the morning
• Damp on external walls, usually in corners where cold bridging is worst
• Musty smell throughout the property

What causes it:

• Inadequate ventilation — particularly in kitchens and bathrooms
• Modern draught-proofing or new windows without trickle vents
• Drying clothes indoors
• Overcrowding or high occupancy
• Poor or absent insulation creating cold surfaces

How it's resolved:

Condensation is primarily resolved through improved ventilation (extractor fans, trickle vents, MVHR in severe cases), better insulation, and behavioural changes. Black mould should be treated with a fungicidal wash before redecorating.

Wittick Building Tip: If you're seeing black mould repeatedly in the same spots, the cause is almost always condensation — not rising or penetrating damp. A dehumidifier can help short-term, but the long-term fix is better ventilation and insulation.

When to Get a Damp Survey

If the source of damp isn't obvious, or if you're buying a property with damp flagged in the survey, it's worth getting an independent damp survey from a qualified surveyor. Be cautious of 'free surveys' offered by damp treatment companies — they have an incentive to recommend treatment regardless of the diagnosis.