How do I evidence damp and mould for a housing disrepair claim?

What this usually means

A housing disrepair claim turns on whether the property is in disrepair that the landlord is obliged to remedy, and whether that disrepair is causing the damp and mould you are experiencing. Mould itself is a symptom; the claim needs to show what is producing it and that the cause is a building failing rather than, say, normal occupation. Landlords frequently attribute damp and mould to 'lifestyle' — cooking, drying washing, not ventilating — so evidence that simply shows mould is present can be countered by that argument. What advances a claim is objective evidence of the underlying cause and its link to a defect or inadequacy in the building.

That evidence is gathered by a proper diagnostic survey, ideally by an independent expert with no interest in the outcome. It records indoor temperature and humidity over time to establish whether the home is at condensation risk and whether the ventilation provided is adequate; it uses thermal imaging to reveal cold surfaces, thermal bridges and missing or failed insulation that cause condensation; and it inspects the fabric for penetrating-damp defects such as failed pointing, render, flashings or guttering, and for rising-damp indicators. By distinguishing the mechanism and identifying the building feature responsible — a cold, uninsulated wall, an absent or broken extractor, a leaking defect — it connects the damp to a disrepair rather than to occupancy.

The result should be a clear, independent expert report that a landlord, solicitor or court can rely on: stating the measured findings, the diagnosed cause, the building defect or inadequacy responsible, and the remedy required. Crucially, an independent building-physics assessment carries weight precisely because it is not selling a treatment and is not the tenant's or landlord's word — it is documented measurement and reasoning. The same report also makes clear what must be put right, which both supports the claim and helps ensure any works actually resolve the problem. Knowing this is what the evidence needs to contain lets you commission the right survey rather than relying on photographs that a landlord can dispute.

Common causes

Signs and symptoms

Establishing responsibility for damp and mould requires separating the contribution of the building from that of occupancy, which is a quantitative question. Every household generates moisture; whether that moisture causes mould depends on the surface temperatures and the ventilation the building provides. If surfaces are cold because walls are uninsulated or bridged, and if the ventilation falls short of what is needed to remove normal moisture, then condensation and mould will occur under ordinary use — making the building the cause. Measurement is what demonstrates this: temperature and relative-humidity logging shows whether surfaces reach the dew point under reasonable conditions, and thermal imaging shows whether the cold surfaces arise from fabric defects rather than from the occupant's behaviour.

The diagnostic distinctions are the same as in any damp survey but the documentation requirement is higher. Condensation is identified from cold surfaces, elevated surface humidity and inadequate ventilation; penetrating damp from rainfall correlation and an identifiable external defect; rising damp from its limited height and salt banding, confirmed rather than presumed. Because the conductance damp meter can mislead, robust evidence rests on logged environmental data, thermal mapping, comparative moisture measurement and fabric inspection, interpreted together. An independent assessment records these objectively and reasons from them to the cause, which is far harder to dispute than a tenant's photographs or a landlord's assertion of lifestyle.

The report's value in a claim lies in its independence and its chain of reasoning: measured findings, diagnosed mechanism, the specific building defect or inadequacy responsible, and the remedy required to resolve it. This converts a contested symptom into documented cause-and-responsibility, the basis on which a disrepair claim proceeds. It also defines the correct remediation — warming and insulating cold surfaces and providing adequate ventilation for condensation, repairing the defect for penetrating damp, addressing the damp-proof course for genuine rising damp — so that, whatever the legal outcome, the work that follows actually fixes the home. A measured, independent building-physics report is therefore the practical foundation of both a credible claim and a genuine resolution.

How to build the evidence for a damp and mould claim

Commission an independent, measured survey that diagnoses the cause, links it to a building defect or inadequacy, and sets it out in a clear expert report — not just a set of photographs.

1. 01

   Document the conditions

   Log the indoor temperature and humidity over time to show whether the home is at condensation risk.

2. 02

   Map the cold surfaces

   Use thermal imaging to reveal cold surfaces, bridges and missing or failed insulation.

3. 03

   Inspect for defects and ventilation

   Check for penetrating-damp defects and whether the ventilation provided is adequate.

4. 04

   Diagnose the cause

   Establish whether it is condensation, penetrating or rising damp and what building feature is responsible.

5. 05

   Produce an independent report

   Set out the measured findings, the cause, the responsibility and the remedy clearly.

6. 06

   Use it to support the claim

   Provide the report to the landlord, solicitor or court as objective expert evidence.

How to prevent it coming back

• Rely on independent, measured evidence rather than photographs alone.
• Document the cause and the building defect, not just the mould.
• Use logged data and thermal imaging that a landlord cannot easily dispute.
• Ensure the report states the remedy required.