Damp and mould inspection checklist

How to use this damp and mould checklist

Work through the sections in order: background and questions first, then outside, then inside room by room, then readings and ventilation. Damp is diagnosed from a pattern of evidence, not from any single reading, so the checklist is built to collect that pattern and to record what you could not see.

Many cases have more than one cause. A leaking gutter makes a wall wet and colder, and the colder wall then attracts condensation. Keep an open mind until the external check, the readings and the conditions all point the same way.

The four types of damp and how to tell them apart

The GOV.UK guidance for rented housing providers, Damp and mould: understanding and addressing the health risks, describes four types of damp: condensation, penetrating, rising and traumatic. Mould is a fungus that grows wherever a surface stays damp for long enough, whatever the source of the moisture.

How to read a moisture meter on walls without overclaiming

A pin-type moisture meter measures electrical resistance and is calibrated for timber. In timber, with the right species setting, it gives a useful estimate of moisture content. In brick, stone, plaster and mortar it does not: the number is a relative reading, and scales such as wood moisture equivalent are not a percentage of water in the wall.

Several things raise readings without the wall being wet at depth: hygroscopic salts left by past damp or old chimney flues, carbon or foil in plaster and wallpaper, metal fixings, and condensation on the surface. Non-invasive meters are quick for mapping the extent of a damp area, but they read only near the surface and are affected by density and hidden metal.

Treat meter readings as a map. Take them in a grid, compare them with a control area you know to be dry, and look for a pattern that fits one cause. Where the diagnosis matters, for example before anyone recommends a new damp-proof course, confirm it with drilled samples tested for moisture content (by carbide or oven-drying) and for hygroscopic moisture, which separates water from the ground from moisture drawn out of the air by salts. The GOV.UK guidance says chemical testing is the most appropriate way to confirm rising damp.

How to check for condensation: temperature, humidity and dew point

Condensation forms when a surface is at or below the dew point of the air next to it. To test that on site you need three numbers: the air temperature, the relative humidity, and the temperature of the suspect surface.

For example, air at 20°C and 60% relative humidity has a dew point of about 12°C. A window reveal or external corner measuring 12°C or colder is wet now. One at 14°C is close to the line and likely to get wet overnight, when the heating goes off and the household is breathing moisture into closed bedrooms. You can check your own figures with the free DampApp Pro dew point calculator.

Mould does not need liquid water. Condensation risk standards such as BS EN ISO 13788 use a surface relative humidity of 80%, sustained over time, as the limit for avoiding mould growth. That is why cold spots grow mould even when they never look wet, and why surface temperatures matter more than the room humidity on its own.

A single visit is a snapshot. The heating may be on, the windows open, or nobody may have cooked or showered that day. Record what happened in the home that day and, for suspected condensation, leave data loggers for a week or two so you can see conditions through the night.

Ventilation checks that find the cause

Cooking, showering, washing and drying clothes all release moisture, and a home has to be able to remove it. The GOV.UK guidance is clear that it is unreasonable to blame damp and mould on tenants’ lifestyle: the fundamental causes are building deficiencies, inadequate ventilation, inadequate heating or poor energy efficiency.

So check what the home gives people to work with. Look for extract fans that are missing, switched off at an isolator, too noisy to be used, or recirculating rather than ducted outside; trickle vents painted or taped shut; internal doors with no gap beneath them; and whole-house systems on the wrong setting or with blocked filters. Where you have the equipment, measure extract flow and compare it with Approved Document F. DampApp Pro includes ventilation testing so the results sit in the same report as the readings.

What to put in a damp and mould report

A good report lets someone who was not there understand what you found, why you think it happened, and what to do first.

1. The household’s account, including any health concerns they raised, recorded rather than assessed.
2. Conditions on the day: weather, temperatures, humidity and whether the heating was on.
3. Findings room by room, with numbered, captioned photographs.
4. Readings on a plan or wall profile, with the meter type and scale stated.
5. The likely cause or causes, the evidence for each, and anything not yet confirmed.
6. Recommendations in priority order: make safe, fix the source, then prevent it coming back.
7. Limitations: what you could not access or test.
8. A re-inspection date. GOV.UK recommends inspecting at least 6 weeks after remedial work to check the damp and mould have not returned.

Keep what you measured separate from what you concluded. “High relative readings along the base of the front wall, falling away higher up, with a salt band at the tide mark” is evidence. “Rising damp” is a conclusion, and it needs that evidence, and ideally samples, behind it. You can see how a finished report sets this out in our fictional damp and timber survey example.

Damp, mould and the law for landlords

In England, damp and mould growth is one of the hazards assessed under the Housing Health and Safety Rating System, and councils must take action on Category 1 hazards. Most rented homes must also be fit for human habitation under the Landlord and Tenant Act 1985 as amended by the Homes (Fitness for Human Habitation) Act 2018, and freedom from damp is one of the matters that decides it. Social landlords must also meet Awaab’s Law timescales for damp and mould that presents a significant or emergency risk of harm.

The GOV.UK guidance tells landlords to act without waiting for medical evidence, to photograph mould before it is removed, to tackle the underlying cause rather than only cleaning the surface, and to use qualified professionals rather than assume they can diagnose damp themselves. For the social housing timescales, use our Awaab’s Law checklist; for the wider hazard assessment, see the HHSRS hazard checklist.

Staying safe on site

Mould spores and cleaning products can harm the person doing the work too. GOV.UK advises a mask, gloves and goggles when removing mould, and caution when lifting wallpaper or carpet, which can release a lot of spores at once. Take the same care when opening up to investigate, and consider the risk of asbestos before drilling or cutting into textured coatings, floor tiles or boards in older buildings.