What might be happening here?
Different causes can look similar. These are possibilities to investigate, not a diagnosis of your property.
Mould around a window or outside corner
Record the exact location and pattern. Ask whether glazing, window seals, external defects, heating and cold surfaces need checking together. A photograph identifies the affected area but does not establish why it is happening.
A problem behind furniture
Ask the inspection to include accessible areas around and behind furnishings, with help where moving them would be unsafe. A cold wall and limited airflow are questions to investigate, not grounds for automatically blaming the resident.
A room that stays cold or becomes too hot
Describe when the room is uncomfortable, whether it is usable for sleeping and whether the heating or window controls work. Request investigation of the building and services, alongside any support needed to use them.
A patch beneath the roof or next to a bathroom
Include adjoining spaces and earlier leaks in the history. Do not assume that every bedroom patch is condensation; the position of the roof, pipework or neighbouring accommodation may matter.
What monitoring can—and cannot—tell you
Start with the question. Record where a device is installed, whether it is working and the period its readings cover.
Room temperature and relative humidity
Useful for
Time-series readings can help describe night-time and daytime conditions. Record the position of the device, the period covered and any gaps; avoid a spot dominated by a radiator, direct sun or a draught.
What it cannot establish
These are air measurements at a particular location. They do not measure mould species, diagnose illness or prove the condition of a colder wall.
Surface-temperature assessment
Useful for
A competent assessor can compare an affected surface with the room conditions and inspect the construction. Thermal images may help locate differences that warrant further investigation.
What it cannot establish
An image is not a moisture or mould test. Interpretation depends on conditions and the construction; a colour alone does not identify the defect.
CO₂ where ventilation is a question
Useful for
In an occupied room, a suitable CO₂ monitor may help explore ventilation patterns. Use manufacturer instructions and record enough context to interpret the readings.
What it cannot establish
CO₂ is not carbon monoxide. A CO₂ monitor is neither a CO alarm nor a comprehensive air-quality, mould or occupancy assessment.
After the repair
Ask what has changed physically, rather than accepting a fresh finish as the whole repair.
Include the resident’s account at follow-up: can the room be used, have the marks returned, and are heating and ventilation usable?
Escalate continuing or worsening problems through the landlord’s repairs and complaints routes. Use the nation guidance for the applicable process.
Your evidence checklist
Tick the records you already have. Unticked items are prompts—not a reason to delay reporting.
0 of 5 records marked available
Useful details to put in your report
- Where in the bedroom is the problem?
- How is sleep or use of the room affected?
- What has been reported or repaired before?
- What access or communication support would help?
Notes stay in this page; they are not sent to us or your landlord. Download or copy them before leaving. Avoid including names, addresses or sensitive information.
Sources behind this guide
Knowledge Centre practical guidance, informed by the sources below. Technical advice is not the same as legislation; each source’s scope is shown.
- UK GovernmentUnderstanding and addressing the health risks of damp and mould in the home ↗
England guidance. Technical sections on sources of moisture, inspection, ventilation and follow-up; not a UK-wide repair timetable.
- Royal Institution of Chartered SurveyorsDamp and mould: consumer guide ↗
Professional-body advice on moisture sources and building investigation. Not legislation.
- Health and Safety ExecutiveUsing CO₂ monitors ↗
Workplace guidance used only for measurement principles and limitations. Its workplace figures are not presented as domestic legal limits.
- Housing OmbudsmanDamp and mould learning resource ↗
England: resident impact and landlord learning. Technical monitoring is not a substitute for responding to reports.
Guide sources checked .