How to Deal with Mould in a Rental Property: A Landlord's Complete Guide

When a tenant reports mould, you must log the report, investigate promptly using a qualified inspector, fix the underlying cause, and document every step. Under Awaab’s Law and the Homes (Fitness for Human Habitation) Act 2018, delay or superficial treatment can expose you to serious legal, financial, and reputational risk.

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1. What are a landlord’s legal duties when mould is reported?

The moment a tenant reports mould or damp, your legal duty begins. You are required to:

1. Investigate promptly – identify the cause, not just the visible mould.
2. Arrange appropriate remediation – fix the underlying defect and treat the mould safely.
3. Keep evidence – maintain a clear paper trail of what was reported, what you did, and when.

Under Awaab’s Law (now extended to the private rented sector), you must:

• Acknowledge and investigate within 14 days of the report.
• Complete emergency repairs within a specified period where there is a serious risk to health.

Alongside this, the Homes (Fitness for Human Habitation) Act 2018 requires that rented homes are fit to live in throughout the tenancy. Persistent damp and mould can render a property unfit, exposing you to:

• Claims for compensation.
• Enforcement action by the local authority.
• Rent repayment orders and potential licensing issues.

Your immediate three-step response

As soon as you receive a report of mould or damp:

1. Log the report with a timestamp
   • Record: date, time, who reported it, how (email, phone, portal), and a brief description.
   • This is your legal start clock for Awaab’s Law and any later dispute.
2. Arrange a qualified inspection within 14 days
   • Instruct a PCA-accredited contractor or CSRT-qualified surveyor.
   • Confirm the inspection date in writing to the tenant.
   • Make clear that access is required and how long the inspection will take.
3. Act on the findings and document everything
   • Approve recommended remediation without undue delay.
   • Keep copies of the inspection report, quotes, work orders, and completion confirmations.
   • Follow up with the tenant to confirm the issue is resolved and record their response.

Failure to follow this sequence can be used as evidence that you have not taken reasonable steps to keep the property fit and safe.

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2. What types of damp and mould are found in rental properties?

Understanding the type of damp is essential. Treating the wrong cause wastes money and leaves you exposed.

2.1 Condensation mould

What it is:

Condensation mould is the most common type in UK rentals. It occurs when warm, moist air meets cold surfaces, causing water to condense and feed mould growth.

Typical signs:

• Black or dark mould patches on:
  • External walls.
  • Corners of rooms.
  • Around window reveals.
  • North-facing or cold surfaces.
• Condensation on windows, especially in the morning.
• Musty odours in bedrooms, bathrooms, and behind furniture.

Common structural causes:

• Inadequate or non-functioning mechanical extraction in kitchens and bathrooms.
• Blocked, missing, or closed trickle vents and background ventilation.
• Thermal bridging at wall junctions and around windows.
• Poor or insufficient insulation on external walls.

Role of tenant behaviour:

Tenant lifestyle can contribute (e.g. drying clothes indoors, not using extract fans, blocking vents). However, you cannot rely on tenant behaviour as a defence until you have:

• Assessed the property for structural and ventilation deficiencies.
• Taken reasonable steps to improve ventilation and insulation where needed.

Courts and local authorities will expect you to show that the building and its systems are adequate before blaming how the property is used.

2.2 Rising damp

What it is:

Rising damp occurs when groundwater travels upward through walls or floors by capillary action.

Typical signs:

• A visible tide mark at low level on walls (often up to 1 metre).
• Salt crystallisation on plaster surfaces.
• Crumbling or decayed skirting boards.
• Damage to floor coverings near external walls.

Key points for landlords:

• Rising damp cannot be solved by redecoration alone.
• It usually requires a damp proof course (DPC) and specialist replastering.
• Any plaster contaminated by hygroscopic salts must be hacked off and replaced.

2.3 Penetrating damp

What it is:

Penetrating damp is caused by water entering through defects in the building fabric.

Typical signs:

• Localised damp patches on walls or ceilings.
• Staining that may worsen during or after rain.
• Peeling paint or blistering plaster.

Common causes:

• Failed or missing pointing.
• Cracked or defective render.
• Blocked or leaking gutters and downpipes.
• Poorly sealed windows and doors.
• Roof defects, such as broken tiles or flashing.

Penetrating damp is often seasonal and may worsen in wet or windy weather.

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3. What does a professional mould inspection involve?

A proper inspection is a technical assessment, not a quick look and a quote. You should instruct a PCA-accredited contractor or CSRT-qualified surveyor and insist on a written report.

3.1 Core elements of a professional inspection

1. Calibrated moisture readings
   • Use of a professional moisture meter to map moisture levels across affected walls, floors, and ceilings.
   • Helps distinguish between condensation, rising damp, and penetrating damp.
2. Relative humidity and temperature monitoring
   • In suspected condensation cases, a data logger may be installed.
   • This provides objective evidence of humidity levels, temperature, and dew point conditions over time.
3. Fabric inspection
   • Examination of: