Letter to Your Landlord About Mould: Your First Formal Notice and What It Must Say
You have already told your landlord about the mould. You texted. Maybe you called. Nothing happened, or they said it would be dealt with and it was not. That informal contact is useful background, but it is not the same as a formal written notice. The moment you send a proper letter with a deadline, the legal clock starts ticking.
What the law says
Section 11 of the Landlord and Tenant Act 1985 places a statutory duty on landlords in England and Wales to keep the structure and exterior of the property in repair, including walls, roofs, windows and drains. Mould caused by structural defects such as a leaking roof, failed cavity wall insulation or inadequate ventilation is almost always the landlord's legal responsibility under section 11. The duty applies regardless of what your tenancy agreement says and cannot be contracted away.
The Homes (Fitness for Human Habitation) Act 2018 goes further. It inserted section 9A into the Landlord and Tenant Act 1985, and applied to new tenancies from 20 March 2019 and to all existing periodic tenancies from 20 March 2020. Section 9A requires that a rented home is fit for human habitation at the beginning of the tenancy and throughout. The legislation lists specific matters that are relevant to fitness, and damp is one of them. A property where mould growth is affecting a bedroom, living room or bathroom and is caused by a structural or maintenance problem is likely to fall below the standard the 2018 Act requires. If it does, you can take your landlord to the county court without needing any prior involvement from the council, and the court can order repairs and award you compensation.
If your landlord is a social landlord, a council or a housing association, a third set of rules applies. Awaab's Law, in section 10A of the Landlord and Tenant Act 1985 as inserted by the Social Housing (Regulation) Act 2023, has applied to damp, mould and emergency hazards in social housing since 27 October 2025. It puts fixed investigation and repair timescales on the landlord rather than leaving it at what is reasonable. It has not yet been extended to private landlords: the government has said it intends to extend it to the private rented sector under the Renters' Rights Act 2025 but has not confirmed a date, so a private tenant should rely on sections 11 and 9A instead.
The key thing these laws have in common is that they require you to have notified your landlord of the problem and given them a reasonable opportunity to fix it before you can take further action. A formal written letter with a clear deadline is how you create that notification on record. Without it, you have a complaint but not a legal trigger.
What your letter needs to include
Your first formal letter about mould should be factual, specific and clear about what you expect to happen next. Include:
- Your name, the property address and the date of the letter
- A factual description of where the mould is, how long it has been present and how it has developed since you first noticed it
- A record of all previous contact with the landlord about the problem, with dates and the method used (text, email, phone, in person)
- Any response your landlord gave, including anything they said they would do and whether they did it
- A statement citing sections 11 and 9A of the Landlord and Tenant Act 1985 as the basis for their obligation to act, and Awaab's Law in section 10A if your landlord is a social landlord
- A specific deadline for them to respond with a confirmed repair date, typically 14 days for an ongoing problem that affects habitability
- A clear statement of what you will do if they do not respond (contact the council Environmental Health team or seek legal advice)
What happens after you send it
Most landlords respond when they receive a formal letter that cites legislation and includes a deadline. It changes the tone from a tenant complaint to a legal notice and many landlords, or their letting agents, know what that means. Keep a copy of the letter and a record of how you sent it. If you email it, that is already documented. If you send it by post, use recorded delivery so you have proof it arrived.
If the deadline passes without a satisfactory response, you move to the next stage. That might be a complaint to the council's Environmental Health team, a referral to the Housing Ombudsman if your landlord is a social housing provider, or a claim in the county court under section 9A of the Landlord and Tenant Act 1985. Each of those routes is stronger when you can show you sent a formal notice, named the relevant law and gave your landlord a reasonable chance to fix it. The letter you send now is the foundation for everything that follows.