Condensation Investigation in London and Surrey
Most mould complaints in flats and rented homes trace back to condensation. Proving it, and separating it from leaks and structural damp, is what makes the fix stick.
Condensation forms when warm, moist indoor air meets a surface cold enough to bring it to its dew point. It shows as black spot mould in corners, behind furniture, around window reveals and on cold external walls, often worst in winter. It is also the category most argued over between tenants and landlords, which is why an independent measurement-based report matters. Since Awaab’s Law, social landlords must investigate and act within fixed timescales, and the same standards are being applied to the private sector.
What DML measures
- Relative humidity and air temperature in affected and unaffected rooms, with dew-point calculation.
- Surface temperatures of walls, reveals and cold bridges using thermal imaging where appropriate.
- Ventilation check: extract fans, trickle vents, kitchen and bathroom extraction, and whether they actually work.
- Moisture profiling to rule out rising or penetrating damp and hidden leaks feeding the mould.
- Occupancy and heating pattern, recorded factually, because it is relevant and because reports that blame tenants without evidence do not stand up.
What the report gives you
A clear finding on whether the mould is condensation-driven, structural, or a leak; the contributing factors in order of importance; and a prioritised scope: for example a working extract fan, a positive input ventilation unit, insulating a cold bridge, or repairing a defect that has been misread as condensation. Mould treatment and fogging are specified only once the moisture source is dealt with, otherwise the mould returns. Works are quoted separately by our team or any contractor.
Who asks for condensation reports
- Landlords and agents responding to a tenant complaint or council notice
- Housing associations and councils meeting Awaab’s Law timescales
- Tenants who need independent evidence that a problem is structural
- Homeowners with recurring mould despite cleaning and heating
We investigate across Greater London and Surrey. See areas we cover.
Frequently Asked Questions
Is condensation the tenant’s fault?
Rarely in a simple sense. Lifestyle contributes, but inadequate ventilation, cold bridging, single glazing and poor insulation are building factors. Our report records the measurements and lets the facts speak.
How is condensation different from a leak?
Leaks produce wet, often localised damage that does not track with weather or season and gives high moisture readings deep in the material. Condensation is surface-led and seasonal. We test for both.
Can you test for mould spores?
Where appropriate we can arrange air or surface sampling. For most domestic cases the priority is proving and removing the moisture source, which is what stops the mould.
Does fogging get rid of mould permanently?
No treatment is permanent if the moisture source remains. Fogging and antimicrobial treatment are the final step after the cause is fixed. See mould fogging.
Do you supply reports for Awaab’s Law compliance?
Yes. Our condensation and mould reports are written to support hazard assessment, timescale compliance and the works specification.
Related services
Related reading: Black mould vs condensation: the difference and how each is treated · What affects the cost of mould removal
Prove the cause of the mould
Independent condensation and mould investigations across London and Surrey.
Last reviewed: 23 October 2026. Independent investigation and written reports. Repairs are quoted separately.