Damp at home: what to record before investigating the cause

Identify each location so another person can find it: room, wall and position relative to a window or corner. A wider photograph establishes the position; a close-up records the mark.

Use a similar framing for subsequent photographs and note the date. Do not alter the apparent edge of staining by retouching the image. Record any drying or repainting of the area.

Record a hygrometer reading with the temperature, time and instrument location. Treat comparisons immediately after moving it to another room cautiously, allowing the stabilisation time specified by its manufacturer.

One number does not describe an entire day. Readings under comparable conditions, supplemented when the problem worsens, are more useful. Identify the instrument without claiming greater accuracy than its specification supports.

In a separate column, note rain, wind and observed external changes. A timing pattern linked to rainfall is a clue to investigate, rather than proof of a particular roof or façade defect.

Also record bathing, cooking, laundry drying and recent wet construction work. There is no need to reconstruct every occupant activity: focus on identifiable events that help compare affected and unaffected days.

Describe the ventilation type and known settings. Note whether air inlets were open and when filters were serviced. The sound of a running unit does not establish adequate air exchange in every room.

Avoid changing numerous settings together merely to obtain a different reading. If a service technician adjusts the system, keep the description and date. Subsequent comparisons should account for the changed conditions.

Include the known layer build-up, insulation product name and construction photographs. With PIR, the particular product and facing matter; simply stating that a wall is insulated does not describe the behaviour of the complete assembly.

Separate confirmed information from assumptions about concealed layers. Mark a missing drawing as unavailable information. Do not assume waterproofing, a vapour control layer or a ventilated cavity merely because a similar house has one.

Prepare a short chronology and a selection of clear photographs for the inspection. Ask which hypotheses require measurements, where investigation is needed and what evidence will support the assessment. The log alone does not conclude the investigation.

Once the cause is identified, retain the repair scope and the method for checking its effect. Compare later observations with earlier ones under similar conditions. An organised record helps assess change without guaranteeing that every concealed problem has been removed.