Executive summary
A moisture survey was carried out at a top-floor flat in south-west London in July 2026. The property is generally in satisfactory condition in relation to damp and moisture. No significant elevated moisture readings or evidence of active dampness were identified in the entrance hallway, living room, bedrooms or kitchen.
The principal defect is moderate mould growth within the bathroom, affecting the ceiling and window areas. Moisture readings within the bathroom were within satisfactory dry parameters at the time of inspection. The mould pattern is consistent with condensation and inadequate ventilation rather than a structural leak. A blocked air vent in the kitchen was also identified and should be cleared to improve background ventilation.
Environmental conditions at inspection
Weather at the time of inspection was dry and clear.
Equipment used
- Protimeter MMS3: comparative electronic moisture readings (pin and non-invasive modes), air temperature, relative humidity and dew point.
- FLIR E4 thermal imaging camera: thermal assessment of surfaces and potential thermal bridges (IR sensor 320 x 240, spectral range 7.5 to 14 micrometres).
Basis and methodology
Non-destructive visual inspection of accessible rooms and surfaces; comparative electronic moisture readings to walls, floors and ceilings; inspection for staining, peeling paint, defective finishes and mould growth; assessment of internal ventilation; measurement of internal air temperature and relative humidity; recording of internal dew point; inspection of accessible chimney breast areas.
Carried out in accordance with the principles of BS 5250:2021 (Management of moisture in buildings) and the Property Care Association Code of Practice for Damp Investigations. No opening of ceilings, walls or floors was undertaken.
Findings summary
| Area | Defect | Likely cause | Status |
|---|---|---|---|
| Entrance hallway | None identified | N/A | Dry |
| Living room | None identified | N/A | Dry |
| Bedroom one | None identified | N/A | Dry |
| Bedroom two | Small historic damp mark to ceiling | Previous roof leak, since repaired | Historic, dry |
| Bathroom | Moderate mould contamination on ceiling and window areas | Condensation due to inadequate ventilation, no mechanical extractor fan installed | Active |
| Kitchen | Air vent blocked or obstructed | Obstruction restricting background ventilation | Active |
Moisture readings
All rooms recorded within satisfactory dry parameters (threshold 200 REL or below) across accessible walls, floors and ceilings, including accessible chimney breasts. The historic ceiling stain in Bedroom two and the stained bathroom ceiling area both read within satisfactory dry parameters at the time of inspection.
Diagnosis
Condensation-related mould growth due to inadequate bathroom ventilation; no active structural damp or leaks.
During bathing or showering, large quantities of water vapour are released into the bathroom. Without adequate mechanical extraction, the warm moisture-laden air remains in the room and meets colder surfaces such as window glass, frames, external walls, ceiling surfaces and corners with limited air movement. When those surfaces fall to or below the dew point (16.6°C during the inspection), condensation forms.
Repeated condensation provides the moisture mould needs to grow, even though the underlying wall or ceiling may read dry during a daytime inspection. The absence of a mechanical extractor fan is a significant contributing factor.
Differential diagnosis
Causes considered and ruled out during the investigation:
| Cause | Why ruled out |
|---|---|
| Penetrating damp or water ingress | Readings within dry parameters; no pattern of active ingress; mould localised to bathroom ceiling and windows. |
| Rising damp | Top-floor flat with no ground-level moisture contact; no elevated readings at skirting or wall bases. |
| Active plumbing leak | No leak pattern in bathroom readings; all accessible areas within dry parameters. |
| Widespread structural dampness | Hallway, living room, bedrooms and kitchen all dry; only localised bathroom mould. |
Risk ratings
Recommendations
A suitably sized mechanical extractor fan ducted directly to the external atmosphere (not into a roof or ceiling void), with a timer or humidity sensor and an overrun of roughly 15 to 30 minutes after use. Ensure adequate replacement airflow (for example a gap beneath the door). Installation to comply with electrical and ventilation building regulations.
Maintain consistent heating in cold periods. Use the extractor during and after bathing. Ventilate briefly where safe. Avoid drying large amounts of laundry indoors without ventilation. Wipe persistent condensation from windows. Keep airflow around external walls and corners. Keep window vents unobstructed.
A follow-up inspection once remediation, the extractor fan, the cleared kitchen vent and any window or ventilation improvements are complete, to confirm no mould regrowth and effective ventilation.
Full window replacement solely on the basis of the bathroom mould. Windows should be assessed on confirmed defects, and improved extraction may resolve the mould without replacement.
Conclusion
The property is dry and in satisfactory condition in relation to structural damp and water ingress. No evidence of widespread active dampness, rising damp, penetrating damp or plumbing leaks was identified.
The principal defect is moderate mould contamination in the bathroom, concentrated on the ceiling and window areas, attributed to condensation from the absence of mechanical extraction combined with moisture generated during bathing. A blocked kitchen air vent should be cleared to restore background ventilation.
With professional bathroom mould remediation, a suitably ducted extractor fan, the kitchen vent cleared, and improved heating and ventilation, the property will remain in good condition. A post-remediation review is advised to confirm effectiveness.
The result
Following professional mould remediation and the installation of a mechanical extractor fan, the bathroom ceiling was fully treated and restored to a clean, mould-free finish. The photographs below show the same ceiling from this survey, before and after the completed work.
Limitations
- Non-intrusive inspection only.
- No removal of plaster, plasterboard or finishes.
- No opening of ceiling voids, cavities or window frames.
- No roof access.
- No inspection of concealed plumbing.
- No air or surface mould sampling.
- Areas concealed by furniture, fittings and fixed finishes could not be fully assessed.
- Environmental readings represent conditions at the time of attendance.
Surveyor sign-off
Surveyor name and certification number redacted in this public sample. Every survey is carried out and signed off by an IICRC-certified surveyor.
Want a report like this for your own property?
This sample shows exactly what you get from a real D&M damp survey: proper moisture readings, thermal imaging, a clear diagnosis and recommendations you can act on. No guesswork, no upsell.
Book a Damp and Mould Survey