Every October the same message arrives: black spots in the corner of the bedroom, behind the wardrobe, along the window reveal. The tenant calls it damp. You suspect it is condensation. Whoever is right, the wall looks the same.
The distinction is not pedantry. It decides who pays, how fast you have to move, and whether a disrepair claim later has anything to stand on. And it is the one step the usual advice skips: most guidance tells you how to respond to damp and mould, not how to work out which of four different problems you are actually looking at.
Not legal advice. This describes the law in England. Wales, Scotland and Northern Ireland run different regimes. Where a hazard is severe or a tenant is unwell, act first and establish the cause alongside, not before.
Why the cause decides who pays
Two provisions of the Landlord and Tenant Act 1985 do the work here.
Section 9A(1) implies into the tenancy a covenant that the dwelling is fit for human habitation at the time the lease is granted and will remain fit throughout the term. It is not a promise to repair on request; it is a standing condition.
Section 10(1) lists the matters that decide fitness, and the third item on that list is "freedom from damp". Section 10(2) adds any hazard prescribed under section 2 of the Housing Act 2004, which is where damp and mould growth enters as a rated hazard.
So far, so bad for the landlord. Then comes the carve-out.
Section 9A(3) says the landlord is not liable where the unfitness is "wholly or mainly attributable to the lessee's own breach of covenant". That is the provision landlords reach for when they think the answer is condensation.
It is a real defence and it is much narrower than it sounds. "Wholly or mainly" is a high bar, "breach of covenant" means breach of an actual term of the tenancy rather than a habit you dislike, and the burden of showing it sits with you.
Primary sources: section 9A and section 10 of the Landlord and Tenant Act 1985 on legislation.gov.uk, both current to August 2026.
The sentence that ends the "lifestyle" argument
The government's guidance on damp and mould, updated 1 April 2026 and written for social and private landlords alike, puts it beyond argument:
> "We are absolutely clear that it is totally unreasonable to blame damp and mould in the home on 'lifestyle choices'."
The same guidance states that the fundamental cause will be building deficiencies, inadequate ventilation, inadequate heating or poor energy efficiency, rather than tenants' normal domestic activities. It is written for social and private landlords together, so a private landlord cannot read it as somebody else's rulebook. (Understanding and addressing the health risks of damp and mould in the home, GOV.UK, updated 1 April 2026.)
Read those two things together with section 9A(3) and the position is workable rather than contradictory:
The practical rule: a property has to cope with an ordinary household. If it only stays dry when the occupier behaves unusually well, the property is the problem.
Four causes, and the tells that separate them
Condensation
Warm moist air meets a surface cold enough to take it below its dew point, and the moisture leaves the air and lands on the wall. Mould follows because mould needs a damp surface, not liquid water.
The tells. It appears on the coldest surfaces, which is why it favours north-facing walls, external corners, window reveals, and the wall behind a wardrobe where air cannot move. It is seasonal, arriving with the heating season and easing in spring. The mould is usually black speckling rather than a stain, and it sits on the surface. Wipe a patch and the plaster underneath is sound.
What it means. Almost never the tenant's fault in law. Cold surfaces mean insulation, thermal bridging or heating that is too expensive to run. Insufficient air changes mean ventilation. Both are yours.
Penetrating damp
Water crossing the wall from outside.
The tells. It is patchy and localised rather than spread along the room, it tracks the weather (worse after driving rain, drying between), and it appears at any height, including high on the wall, which condensation and rising damp do not do. There is usually an external cause you can stand outside and point at: a blocked gutter, a cracked downpipe, failed pointing, a leaking flashing, ground level built up above the damp-proof course.
What it means. Structure and exterior. This is section 11 territory and it is yours without argument.
Rising damp
Groundwater drawn up through masonry by capillary action where there is no working damp-proof course, or where one has been bridged.
The tells. It is confined to the bottom of the wall, typically no higher than about a metre, and it presents as a horizontal tide mark rather than a patch. Above the line the wall is dry. Skirtings and plaster deteriorate, and salts brought up with the water leave a white crystalline bloom and make the surface feel damp again days after it looks dry.
What it means. Yours. It is also far rarer than it is diagnosed, and "rising damp" is the standard misreading of a leak at low level or condensation behind furniture on an external wall.
A leak
Plumbing, a shower tray, a roof, an overflow.
The tells. Localised, persistent and indifferent to the weather and the season. A leak does not improve in July and it does not care whether it rained. Look for the fixture directly above or behind the patch.
What it means. Yours, and usually the cheapest of the four to fix if you find it early.
The visit, in the order that answers the question
You can settle this in one visit if you go in the right order.
What to do once you know
Condensation. Treat it as a building problem, because that is what the guidance says it is. Ventilation first, since it is cheapest and quickest: working extractors in kitchen and bathroom, clear trickle vents, unblocked airbricks. Then the cold surface: insulation, and the heating cost that determines whether the tenant can afford to keep the fabric warm. Improving the EPC rating and reducing condensation are frequently the same job, which is worth knowing while the EPC C deadline is on the horizon.
Penetrating damp. Fix the external defect, then let the wall dry before making good. Replastering a wall that is still taking water buys you a repeat call in six weeks.
Rising damp. Get it properly diagnosed before spending, because the misdiagnosis rate is high and a chemical DPC injection is an expensive answer to a leaking downpipe.
A leak. Trace and fix. Then check for the damage it has already done behind the surface.
In every case, the response clock runs from the moment the tenant tells you, not from the moment you work out the cause.
Where Awaab's Law sits, accurately
Awaab's Law is in force in the social rented sector, from 27 October 2025, with a second phase widening the range of hazards from 30 November 2026. The government has said it intends to take powers to extend the regime to the private rented sector. No commencement date for the private sector has been announced, and anyone quoting you one is guessing. (Awaab's Law in the social rented sector, GOV.UK.)
That is not a reason to relax. The route a private tenant already has is disrepair, under section 9A and section 11, and it does not need a new statute to work. A disrepair counterclaim also has a habit of surfacing in the middle of a possession claim, which is its own problem.
The five mistakes that cost the most
Keeping the evidence without keeping a folder
The awkward part of damp is that the story runs for months: the first message in November, the visit, the photographs, the contractor, the follow-up in February. By the time anyone asks, the pieces are in three inboxes and a phone.
In LetCompliance the tenant reports it in their portal with photographs attached and the clock starts on a dated record. The visit, the contractor, the invoice and the follow-up all attach to the same property, and the whole thread exports as one timestamped file if a council or a court ever asks how it was handled.
That is the difference between believing you responded properly and being able to show it.
Start free, no card needed to run tenant reports, contractor work orders and dated evidence from one login.
Common questions
Is condensation the tenant's responsibility? Normally no. Government guidance is explicit that blaming damp and mould on lifestyle choices is unreasonable, and that the fundamental causes are building deficiencies, ventilation, heating and energy efficiency. A property has to cope with an ordinary household.
When can I rely on section 9A(3)? Where the unfitness is wholly or mainly attributable to the tenant's own breach of covenant, for example vents deliberately sealed or an extractor removed. Normal cooking, washing and drying is not a breach and will not get you there.
How high does rising damp go? Typically no higher than about a metre, with a horizontal tide mark and dry wall above it. Damp above that height is something else.
How do I tell penetrating damp from condensation? Penetrating damp tracks the weather and can appear at any height; condensation tracks the temperature, favours cold surfaces and corners, and eases in spring.
Does Awaab's Law apply to me as a private landlord? Not currently. It is in force in the social rented sector, and the government intends to take powers to extend it to the private sector without having announced a date. Section 9A and section 11 already apply to you.
Do I have to move the tenant out? Not usually, but where a hazard is serious or an occupier is vulnerable or unwell, deal with the risk first and work out the cause alongside it.
2026 UK Landlord Compliance Cheat Sheet
Every Gas Safety, EICR, EPC, deposit and Right to Rent deadline on one printable A4 page. Updated for the Renters’ Rights Act 2025.
- Every UK statutory deadline by document type
- Maximum penalty per breach (HSE, MEES, RtR, deposit)
- What blocks a Section 8 / Form 6A possession claim
- Print-friendly A4 with checkboxes
Frequently asked questions
Is condensation the tenant’s responsibility or the landlord’s?
Normally the landlord’s. Government guidance updated in April 2026 states that it is "totally unreasonable to blame damp and mould in the home on ‘lifestyle choices’", and that the fundamental cause will be building deficiencies, inadequate ventilation, inadequate heating or poor energy efficiency rather than tenants’ normal domestic activities. Cooking, washing and drying clothes indoors are normal domestic activities. A rented property has to cope with an ordinary household, so if it only stays dry when the occupier behaves unusually carefully, the property is the problem.
How do I tell condensation from rising damp or penetrating damp?
By pattern, height and timing. Condensation forms on the coldest surfaces, so it favours north-facing walls, external corners, window reveals and the wall behind furniture; it is seasonal, arriving with the heating season, and shows as black speckling sitting on the surface. Rising damp is confined to the bottom of the wall, typically no higher than about a metre, with a horizontal tide mark, dry wall above it and white salt deposits. Penetrating damp is patchy, appears at any height including high on the wall, and tracks the weather, worsening after driving rain. A plumbing or roof leak is localised, constant, and indifferent to both the weather and the season.
When can a landlord rely on the tenant-behaviour defence?
Section 9A(3) of the Landlord and Tenant Act 1985 removes the landlord’s liability where the unfitness is "wholly or mainly attributable to the lessee’s own breach of covenant". That is a high bar. It needs a breach of an actual term of the tenancy, such as deliberately sealing trickle vents or removing an extractor fan, and the landlord has to be able to show it. Ordinary cooking, washing and drying is not a breach of covenant and does not engage the subsection.
Does the law say a rented home must be free from damp?
Yes. Section 9A(1) of the Landlord and Tenant Act 1985 implies a covenant that the dwelling is fit for human habitation when the lease is granted and remains fit throughout the term. Section 10(1) sets out the matters that decide fitness and "freedom from damp" is the third item on that list, alongside repair, stability, ventilation and others. Section 10(2) adds any hazard prescribed under section 2 of the Housing Act 2004, which is where damp and mould growth enters as a rated hazard.
Does Awaab’s Law apply to private landlords?
Not at present. Awaab’s Law is in force in the social rented sector from 27 October 2025, with a second phase widening the range of hazards from 30 November 2026. The government has said it intends to take powers to extend the regime to the private rented sector but has announced no commencement date for it. Private landlords are already covered by section 9A and section 11 of the Landlord and Tenant Act 1985, which need no new statute to be enforced.
How high up a wall does rising damp go?
Typically no higher than about a metre, because capillary action through masonry has a limit. It presents as a horizontal tide mark with sound dry wall above it, often with a white crystalline salt bloom and deteriorating plaster or skirting below. Damp at head height is not rising damp; it is penetrating damp, a leak, or condensation.
What should a landlord do first when a tenant reports mould?
Acknowledge it and book the inspection, before deciding what caused it. Do not write "condensation" in the first reply: even where it later proves correct, it reads as a refusal and is the sentence most likely to be quoted back. Establish the cause at the visit by checking when it started and what it does, the height and pattern of the affected area, the outside of the same wall, and whether the ventilation actually works. Photograph everything with dates.