Quick Answers
Who is responsible for damp and mould in a block?
It depends on the type. Penetrating damp and rising damp — caused by defects in the building fabric — are the landlord's or RTM company's responsibility. Condensation mould has historically been treated as partly the occupant's issue, but the Decent Homes Standard has shifted this where the building's design or fabric creates conditions that cause mould regardless of occupant behaviour.
Is condensation mould always the tenant's fault?
No — and attributing it automatically to tenant behaviour is no longer an acceptable management response. Where poor insulation, inadequate ventilation, or cold bridging in the building's fabric predictably causes condensation regardless of how the occupant behaves, this is a structural issue. The Decent Homes Standard and the HHSRS require landlords to address these conditions as property defects.
What must an RTM company do when damp is reported?
Acknowledge in writing, inspect physically within a reasonable timeframe, commission a specialist damp survey if the cause is unclear, follow up with written findings and proposed action. Never dismiss without inspection or attribute the cause to the leaseholder without evidence. A written record of every step is essential if the matter escalates to a local authority inspection or Tribunal application.
Why this has become more legally significant: two developments have changed the legal landscape around damp and mould in residential blocks. First, the Awaab Ishak case — in which a two-year-old child died as a result of prolonged mould exposure in a social housing property — prompted statutory reform through Awaab's Law (applying currently to social housing) and a fundamental shift in how regulators and courts view damp and mould as a property management failure rather than a tenant behaviour issue. Second, the Decent Homes Standard was extended to the private rented sector under the Renters' Rights Act 2026, creating enforceable standards for property condition that include freedom from category 1 HHSRS hazards — of which damp and mould growth is one.
The practical implication: a managing agent or RTM company that dismisses a damp or mould report, attributes it to tenant lifestyle without investigation, or fails to act within a reasonable period is now exposed to local authority enforcement under the HHSRS, service charge challenge at the First-tier Tribunal, and potential Decent Homes Standard enforcement under the Renters' Rights Act. The correct response to any damp or mould report is prompt, documented investigation and a clear decision on responsibility and remediation.
Key Takeaways
The type of damp determines who is responsible — diagnosis comes first
Penetrating damp (water entering through defects in walls, roofs, or windows), rising damp (groundwater moving up through walls where the damp-proof course has failed), and condensation mould (moisture from the air condensing on cold surfaces) have different causes and different responsibility allocations. Treating all damp complaints identically — either by automatically sending a contractor to inject a damp-proof course or by attributing everything to condensation from the occupant — produces wrong answers. The first step in any damp report is diagnosis, not remediation.
Penetrating and rising damp are always the landlord's or RTM company's responsibility
Where damp is caused by a defect in the building fabric — failed pointing, cracked render, blocked or overflowing gutters, failed damp-proof course, leaking flat roof, defective window seals — the responsibility for investigation and remediation rests with the landlord or RTM company. This derives from the lease obligation to maintain the structure and exterior. A block managed by an RTM company where penetrating damp is occurring and not being addressed is in breach of the RTM company's maintenance obligations under the lease.
The condensation mould defence is no longer automatically available
The historic management response to condensation mould — "the occupant is not ventilating properly and is generating too much moisture" — is no longer an acceptable first response. Where a property's thermal performance, ventilation design, or cold bridging creates conditions in which condensation is predictable regardless of occupant behaviour, these are building defects. The key question is: would a reasonably behaving occupant in this property predictably experience condensation mould? If yes, the building has a deficiency that falls to the landlord to address.
A damp survey by a qualified specialist is often essential before any remediation
Many damp and mould problems are misdiagnosed — and misdiagnosed damp problems receive the wrong treatment. Rising damp is frequently diagnosed where the actual cause is penetrating damp or condensation; injected damp-proof courses are applied to walls where the dampness is caused by a leaking gutter above; antifungal paint is applied to mould that will return within months because the underlying cause is a cold bridge in the wall structure. A qualified damp surveyor (CSRT or CSSW qualified through the PCA) produces an impartial diagnosis. For any significant or recurring damp problem, this is money well spent before treatment costs are committed.
The Decent Homes Standard applies to private rented flats from 2026
The extension of the Decent Homes Standard to the private rented sector under the Renters' Rights Act 2026 means that private landlords and RTM companies managing rented flats must ensure their properties meet four criteria: the property must be free from category 1 HHSRS hazards, it must be in a reasonable state of repair, it must have reasonably modern facilities, and it must have efficient heating and insulation. Damp and mould growth reaching the threshold of a category 1 hazard causes the property to fail the first criterion. Local authorities can enforce compliance through improvement notices.
Communal area damp is always the RTM company's responsibility
Where damp or mould appears in communal corridors, stairwells, lobbies, or other common parts, this is unambiguously the RTM company's maintenance obligation. There is no shared responsibility question in the communal areas — the RTM company maintains them and must address any condition that makes them damp or mouldy. Communal area mould often indicates a building fabric defect (leaking roof, failed external render, blocked drainage) that will also affect individual flats if not addressed. Communal damp should be treated as an early warning signal for the building rather than as an isolated maintenance task.
The Three Types of Damp — and Why the Distinction Matters
Before any question of responsibility can be answered, the type of damp must be identified. Each type has a different cause, requires different remediation, and has a different responsibility allocation.
Penetrating damp
Water entering through defectsWater enters the building through a defect in the external fabric — failed pointing, cracked render, blocked or leaking gutters, defective flashings, failed window seals, or a leaking flat roof. It typically produces damp patches that appear on external walls or below roof lines, often after or during heavy rain. The pattern of damp follows the water's path through the building fabric.
Signs: damp patches on external walls, damp appearing after rain, tide marks, peeling paint or wallpaper on external-facing surfaces.
Landlord / RTM responsibilityRising damp
Groundwater through wallsGroundwater rises up through walls from the ground by capillary action, typically where the damp-proof course (DPC) has failed, is absent, or has been bridged by soil or paving built up against an external wall. It produces damp in the lower sections of walls, typically up to around one metre high, often with a tide mark and salt deposits. True rising damp is actually less common than often diagnosed.
Signs: damp consistently at low level on walls, tide marks, white salt deposits, not related to rainfall timing.
Landlord / RTM responsibilityCondensation mould
Moisture from air on cold surfacesWarm, moist air produced by cooking, bathing, and breathing meets cold surfaces — typically cold external walls, windows, and corners — and the moisture condenses. Mould grows where condensation is persistent. The extent to which this is the occupant's or the building's responsibility depends on whether the building's thermal performance and ventilation design make condensation predictable regardless of reasonable occupant behaviour.
Signs: black or green mould on cold surfaces, in corners, behind furniture on external walls, around windows.
Investigate cause before assigningWho Is Responsible for What
| Situation | Responsibility and Basis |
|---|---|
| Penetrating damp from failed external fabric | Landlord / RTM — defect in the structure or exterior that the lease requires the landlord to maintain. Inspect, identify the ingress point, and carry out remedial works to the external fabric as a matter of urgency. Do not treat the internal symptoms until the external cause is resolved. |
| Rising damp from failed DPC | Landlord / RTM — structural defect in the building fabric. Commission a proper damp survey before treatment; many supposed rising damp cases are actually penetrating damp or condensation and are misdiagnosed. |
| Damp from a communal pipe leak | Landlord / RTM — communal service installation is the RTM company's maintenance responsibility. Repair promptly and record the cause, remediation, and any damage caused to affected flats. Buildings insurance typically covers resulting damage to flats below. |
| Condensation mould — poor building thermal performance | Landlord / RTM — where cold bridging, poor insulation, or inadequate ventilation design predictably causes condensation regardless of occupant behaviour, this is a building defect. Improvement works to ventilation or insulation are the landlord's responsibility. |
| Condensation mould — occupant behaviour a significant factor | Shared / investigate — where the building's thermal performance is reasonable and the condensation mould is primarily driven by occupant behaviour (cooking without extractors, drying laundry indoors without opening windows), responsibility is more nuanced. Provide advice and support on ventilation, but still inspect the building fabric before concluding the building is not contributing. |
| Damp from a leaking flat above | Investigate source — if the leak originates from within the flat above (appliance failure, overflowing bath), the occupant of the flat above may bear liability. If the leak is from a communal pipe, the RTM company is responsible. Identify the source before assigning liability. Document contemporaneously and notify buildings insurance promptly. |
| Damp entirely within a leaseholder's demise, caused by their own works or conduct | Leaseholder — where damp is caused by the leaseholder's own unauthorised works (blocking a vent, removing insulation, creating a cold bridge through unauthorised removal of internal walls) the leaseholder bears responsibility for remediation. Document carefully and enforce through the lease breach process if the leaseholder does not act. |
The Decent Homes Standard and Damp and Mould
The Decent Homes Standard (DHS) was extended to the private rented sector under the Renters' Rights Act 2026. It requires that all private rented properties meet four criteria. The first criterion — and the most relevant to damp and mould — is that the property must be free from category 1 hazards as defined under the Housing Health and Safety Rating System (HHSRS).
Damp and mould growth is one of the 29 HHSRS hazard categories. Where damp and mould in a property reaches the threshold of a category 1 hazard (a serious and immediate risk to the health and safety of occupants), the property fails the DHS and the local authority can intervene.
What "category 1 hazard" means in practice for damp and mould:
- Persistent, extensive mould growth on walls and ceilings that cannot reasonably be controlled by the occupant
- Damp that affects sleeping areas and creates ongoing exposure to mould spores
- Damp that is sufficiently severe to damage the fabric of the property or the occupant's belongings
- Damp arising from a structural defect that the landlord is aware of and has not addressed
Awaab's Law — inserted into social housing legislation following the Awaab Ishak case — requires social housing providers to investigate and begin remediation of damp and mould within specific statutory timeframes (investigation within 14 days of a report, remediation begun within seven days for emergency cases). While Awaab's Law currently applies to social housing, the direction of travel in policy and regulation is clearly towards extending similar obligations to the private rented sector. Managing agents and RTM companies who are applying the same response urgency to damp reports that social housing providers must meet are ahead of the regulatory curve. Those who continue to treat damp reports as low-priority maintenance requests are increasingly out of step with the legal and regulatory environment.
HHSRS Assessment and What It Means for Blocks
The Housing Health and Safety Rating System is the methodology used by local authority environmental health officers to assess property hazards. It scores hazards based on the likelihood of harm and the severity of potential harm to the most vulnerable likely occupant.
For damp and mould in a block of flats, the HHSRS assessment considers:
- The extent and persistence of the mould growth
- The location of the mould (bedrooms and areas where occupants spend significant time are weighted more heavily)
- The cause and whether it is attributable to a building defect or to occupant behaviour
- The vulnerability of the occupants (children, elderly, immunocompromised individuals face higher risk from mould exposure)
- The evidence of the landlord's response to previous reports — a landlord who has been notified and has not acted is in a worse position than one who has not yet been informed
Where the local authority assesses a category 1 hazard under the HHSRS, they have a duty to act. They can serve an improvement notice requiring the landlord to carry out specified works within a specified period, or in urgent cases an emergency remedial action notice requiring immediate works. Where a landlord fails to comply with an improvement notice, civil penalties apply and the failure creates further exposure for the RTM company.
What to Do When a Damp or Mould Report Comes In
Acknowledge in writing immediately
Acknowledge the report on the day it is received, in writing. State that you have received the report, that you will arrange an inspection, and that you will follow up with a response within a specified number of working days. This creates a contemporaneous record of when the report was received and ensures the leaseholder or tenant knows their report has been logged. Do not make any assessment of cause or responsibility at this stage.
Arrange a physical inspection promptly
Inspect the affected area in person — ideally within five to ten working days for non-urgent cases. The inspection should assess the extent of the damp and mould, identify visible possible causes, and produce a written report with photographs. Do not rely on a description from the leaseholder or tenant without a physical inspection. The inspection is the foundation of the diagnosis, and the diagnosis determines the next steps.
Commission a specialist damp survey if the cause is unclear
Where the initial inspection does not clearly identify the cause — or where the property manager suspects the cause may be misidentified — commission a survey by a qualified damp surveyor (CSRT or CSSW qualified through the Property Care Association). A specialist survey produces an impartial, documented diagnosis that can be relied on if the matter is disputed. It also prevents the common and expensive error of treating the wrong type of damp with the wrong remedy.
Identify the cause and assign responsibility clearly
Based on the inspection (and survey if commissioned), determine the type of damp and its cause. Apply the responsibility framework from the table above. Where the cause is a building fabric defect, the RTM company is responsible for remediation. Where the cause is genuinely occupant behaviour in a building that performs to a reasonable standard, provide advice and guidance — but still document the building's condition to evidence that it is not contributing to the problem.
Act on the cause — not just the symptoms
Treating mould with antifungal paint while the underlying cause remains unaddressed is not a solution — it is deferral. The mould will return, the leaseholder will report it again, and each recurrence increases the risk of HHSRS enforcement. The correct approach is to remedy the cause first (repair the failed guttering, re-point the external wall, upgrade the ventilation) and then treat the internal symptoms once the cause is resolved. Only treating symptoms also creates significant liability if the matter escalates.
Follow up in writing and confirm resolution
After remediation works are completed, follow up with the occupant in writing to confirm the works have been carried out and ask whether the problem has resolved. At least one post-remediation check — ideally six to eight weeks after the works, when the next damp season arrives or when the next period of rain occurs — is good practice. Close the matter in writing only when the occupant confirms the problem has not recurred. Keep the full file — report, inspection notes, survey, works records, correspondence, and resolution confirmation — for a minimum of six years.
Why Documentation Is as Important as Remediation
In any damp or mould matter that escalates to a local authority inspection, a Tribunal application, or a legal claim, the quality of the RTM company's documentation is often as important as the quality of the remediation itself.
A local authority officer inspecting a property following a tenant's complaint will ask: when was the problem first reported, what did the landlord do in response, how quickly, and what was the outcome? An RTM company with a clear file showing immediate acknowledgement, prompt inspection, specialist survey, identified cause, remediation of the cause, and post-remediation follow-up is in a strong position. An RTM company with no file — or a file showing a complaint received months before any action was taken — is in a poor position regardless of how good the eventual remediation was.
For how the Decent Homes Standard applies more broadly to your block's maintenance obligations, see Decent Homes Standard: What the Private Rented Sector Rules Mean for Landlords. For how annual block inspections should capture early warning signs of damp, see Annual Block Inspections: What a Competent Managing Agent Checks Every Year. For how planned preventative maintenance reduces the likelihood of building fabric failures that cause penetrating damp, see Planned Preventative Maintenance: Why Your Block Needs a 5-Year Schedule.
Frequently Asked Questions
It depends on the type. Penetrating damp and rising damp — caused by building fabric defects — are the landlord's or RTM company's responsibility. Condensation mould has historically been treated as partly the occupant's issue, but where the building's design, insulation, or ventilation creates conditions that cause mould regardless of reasonable occupant behaviour, this is a structural defect. The Decent Homes Standard, now applying to the private rented sector, requires properties to be free from category 1 HHSRS hazards — which includes damp and mould growth at a serious level. Automatic attribution of condensation mould to tenant lifestyle without investigation is no longer an acceptable response.
The position has changed significantly. Historically, condensation mould was attributed to tenant behaviour — insufficient ventilation, excessive moisture generation. The Awaab Ishak case, Awaab's Law in social housing, and the Decent Homes Standard extension to the private rented sector have shifted this. Where the building's thermal performance, ventilation design, or cold bridging creates conditions in which condensation is predictable for a reasonably behaving occupant, the building has a deficiency that falls to the landlord. Always investigate the building's contribution before concluding the occupant is solely responsible.
The Decent Homes Standard is a set of property condition criteria now applying to the private rented sector under the Renters' Rights Act 2026. One of its four criteria requires properties to be free from category 1 HHSRS hazards. Damp and mould growth is one of the 29 HHSRS hazard categories — where it reaches a serious and immediate risk to occupants, it becomes a category 1 hazard and the property fails the DHS. Local authorities can serve improvement notices on landlords requiring remediation within specified timeframes. Failure to comply creates civil penalties and — where the block is managed by an RTM company — further exposure at the First-tier Tribunal.
Acknowledge in writing immediately. Arrange a physical inspection within five to ten working days. Commission a specialist damp survey if the cause is unclear. Identify the cause and responsibility using the type-of-damp framework. Act on the cause first, then treat the symptoms. Follow up after remediation to confirm resolution. Keep a full documented record of every step. Do not dismiss without inspection, attribute to the leaseholder without evidence, or treat symptoms only. A clear file is the RTM company's best protection if the matter escalates.
Yes. Where the landlord or RTM company has failed to address a damp or mould problem within the landlord's lease maintenance obligation, leaseholders can apply to the First-tier Tribunal. They can also refer the matter to the local authority, which has HHSRS enforcement powers. Under the Decent Homes Standard provisions of the Renters' Rights Act 2026, private sector tenants have direct enforcement rights where the landlord fails to remedy DHS failures within specified timeframes. A landlord with a clear documented response record is far better placed at a Tribunal hearing than one with none.
Managing a block where damp reports are not being resolved?
Neon manages damp and mould reports systematically — prompt inspection, specialist surveys where needed, cause-first remediation, and full documentation throughout. If your block has persistent damp issues that have never been properly investigated, talk to us about taking over management and getting them resolved.
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