Mould in Rental Property — Landlord Legal Obligations in London

Is Mould the Landlord's Responsibility?

Whether mould in a rental property is the landlord's or tenant's responsibility depends on its cause — and this is where many disputes arise. The law is clear: structural dampness is the landlord's responsibility. Condensation from tenant behaviour is more nuanced, but recent legislation and case law have significantly increased landlord obligations.

Causes of Mould and Who Is Responsible

Structural Dampness — Landlord's Responsibility

• Rising damp — moisture travelling up through walls from the ground. Caused by failed or absent damp proof course (DPC). Structural repair required.
• Penetrating damp — water entering through the external envelope (roof, walls, windows). Caused by missing/damaged roofing, cracked rendering, failed window seals, blocked gutters. Landlord must repair.
• Plumbing leaks — any water ingress from failed plumbing (dripping pipes, failed shower seals, overflow from blocked gutters) is the landlord's maintenance obligation under Section 11.

Condensation — A Grey Area Becoming Clearer

Condensation mould — caused by moisture-laden air from cooking, bathing, breathing and drying clothes condensing on cold surfaces — has traditionally been treated as the tenant's problem (inadequate ventilation by the occupants). However, the position has shifted:

• The Housing Health and Safety Rating System (HHSRS) classifies severe mould as a Category 1 hazard that landlords must address
• Awaab's Law (Social Housing Regulation Act 2023) — while currently applying to social housing, is expected to extend to private rentals and has already influenced court decisions
• Poor ventilation in the property itself (inadequate trickle vents, no mechanical extraction in bathroom/kitchen) is the landlord's maintenance obligation

The HHSRS and Landlord Action Requirements

Local housing authorities can inspect properties under the HHSRS and issue improvement notices if damp and mould constitutes a Category 1 or Category 2 hazard. A Category 1 hazard requires the landlord to take action; failure to comply can result in:

• Emergency prohibition orders
• Local authority carrying out works and recharging the landlord
• Civil penalties of up to £30,000
• Entry on the Rogue Landlord Database

Awaab's Law Timescales (Expected for Private Sector)

Under Awaab's Law, landlords must:

• Investigate a damp or mould complaint within 14 days
• Start repair work within 7 days of investigation
• Complete emergency repairs within 24 hours

These specific timescales currently apply to social housing, but landlords should treat them as a best-practice benchmark — courts have used similar timescales in considering whether private landlords responded reasonably.

What Remediation Is Required?

For structural damp and mould, remediation must address the root cause — not just treat the surface mould. Surface mould treatment (anti-fungal paint, bleach cleaning) without fixing the underlying moisture problem will result in rapid recurrence and will not satisfy legal requirements. For plumbing-related dampness, a Gas Safe engineer or qualified plumber should identify and repair the source leak before mould remediation takes place.