Damp vs mould: knowing the difference (and what your landlord owes you)

"Damp" and "mould" get used interchangeably, but they're different things, and your landlord's legal position differs depending on which you've got.

This isn't pedantry. When you write a complaint letter, naming the issue correctly strengthens your case.

What is damp?

Damp is moisture in the walls, floor, or ceiling of a building. It has three main causes, and each has a different fix.

Penetrating damp

Water getting in from outside, through a crack in the wall, a broken roof tile, a blocked gutter, a leaking pipe, faulty rendering, or rising damp from the ground.

Penetrating damp shows as tide-marks, damp patches that don't dry, or bubbling paint and plaster. The wall feels cold to the touch and may smell musty.

Cause: structural defect or building failure. Landlord's duty: investigate, identify the source, fix the cause, not just patch the symptom.

Rising damp

A specific subset of penetrating damp where moisture rises from the ground through brick or stone walls. Usually shows as a tide-mark up to 1-1.5 metres above floor level and white salt deposits on the wall.

Cause: failure of the damp-proof course (DPC), which most homes built after 1875 should have.

Landlord's duty: install or repair the DPC. This is a significant works job, not a paintbrush job.

Condensation damp

Different cause: warm humid air meeting cold surfaces. Showers, cooking, drying clothes indoors, breathing, they all add moisture to the air. When that air hits a cold wall or window, water condenses out and runs down or pools.

Condensation tends to be worst in bathrooms, kitchens, and bedrooms with cold external walls. It often shows up around windows, in corners, and behind furniture.

Cause: usually a combination of inadequate ventilation, inadequate insulation, and condensation-prone behaviour (drying clothes indoors).

Landlord's duty: ensure adequate ventilation (working extractor fans, vents, openable windows) and adequate insulation. The landlord cannot defeat your claim by saying "you should ventilate more", adequate ventilation IS their responsibility if the original design didn't include it.

What is mould?

Mould is a fungus that grows on damp surfaces. The most well-known is Stachybotrys chartarum, black mould, but there are also white, green and yellow varieties.

Mould requires damp to grow. If you've got mould, you've got damp. Fixing the mould (bleach, paint over it) without fixing the underlying damp will see the mould return within weeks.

The health risks

This is where Awaab Ishak's case changed the law.

Damp and mould cause:

• Respiratory infections (especially asthma exacerbations)
• Allergic reactions
• Eczema and other skin conditions
• In severe cases (like Awaab's), death

Children, elderly people, and those with pre-existing respiratory or immune conditions are at highest risk. Under Awaab's Law, the landlord's duty to act faster applies specifically when there's a vulnerable occupant.

What to put in your complaint letter

When you report damp or mould, be specific. The right words trigger the right duties.

Don't write: "There's damp in my bedroom."

Write: "Penetrating damp on the north wall of the master bedroom, with visible black mould approximately 1 metre x 0.5 metre area. The damp has worsened over the last 6 weeks. Photographs attached, dated [date]. I have a 4-year-old daughter with asthma."

That sentence triggers:

• Section 11 (structural repair duty)
• Homes (Fitness for Human Habitation) Act (the room isn't fit)
• Awaab's Law (vulnerability + health risk = emergency or urgent category)

Our free letter builder generates this kind of formal letter automatically.

What if the landlord blames you?

"You don't ventilate enough." "You dry clothes inside." "You don't open windows."

These are the standard deflections. They are not a defence if:

• The property doesn't have working extractor fans in kitchen and bathroom
• Windows are stuck shut, draught-stripped to the point of not opening, or absent
• The home is so under-insulated that walls run consistently below dew point
• The damp is on external walls, in corners, or behind furniture (all classic condensation patterns)

Document anything the landlord says blaming you. Their own words can become evidence.

When to claim

If your damp or mould has been reported for more than 21 days with no proper action:

1. Send a stage-2 complaint citing Awaab's Law (for a significant hazard: investigate within 10 working days, complete the safety work within 5 working days of the investigation ending, written summary within 3 working days)
2. If the harm is significant, consider a legal claim, call us free on 0800 030 4669 for an honest assessment

You don't have to take this on alone. Call us free on 0800 030 4669, send the form, or message us on WhatsApp.

Sources: Section 11, Landlord and Tenant Act 1985 (legislation.gov.uk); Homes (Fitness for Human Habitation) Act 2018 (legislation.gov.uk).

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