After heavy rain: what an owner should check before everything dries.

Why this matters

A strong rain event can reveal information that disappears within hours. Water lines dry. stains fade. drains empty. staff clean the floor. A photograph taken the next day may show almost nothing.

The purpose of this check is not to diagnose a leak. It is to preserve the condition before evidence is lost and to identify where specialist investigation should begin.

First rule: protect people and electrical systems

Do not inspect a roof, wet ceiling, flooded plant room or live electrical area when conditions are unsafe. Isolate the affected zone and use the appropriate responsible contractor or specialist.

Record the event before cleaning

Capture:

• date and approximate time;
• when the rain started and stopped;
• whether wind direction was unusual;
• which doors and windows were open;
• whether AC, pumps and extraction were operating;
• photographs and short video before drying or cleaning;
• the first visible location and the later spread;
• whether the condition had occurred before.

A simple marked-up floor plan is more useful than twenty unlabelled close-ups.

Walk the exterior while the water route is still visible

Ground and landscape

Check whether water:

• falls toward or away from the building;
• collects beside external walls;
• crosses door thresholds;
• overflows from planters;
• emerges from retaining walls;
• bypasses channels or drains;
• has nowhere visible to discharge.

Terraces and pool edges

Look for:

• ponding at doors;
• water trapped between tile falls;
• channels filled with leaves or construction debris;
• drains higher than the surrounding finish;
• overflowing balance tanks or pool routes;
• water moving under external doors.

Roofs and gutters

From a safe location, observe:

• standing water after rain has reduced;
• blocked strainers;
• water overtopping gutters;
• overflow paths;
• discharge against walls or foundations;
• staining below parapets, outlets and penetrations.

Do not walk onto a wet roof without safe access and authorisation.

Walk the interior by room and height

Record whether the first sign appears:

• at the bottom of a wall;
• below a window or door;
• at a ceiling junction;
• around a penetration;
• below a bathroom or terrace;
• inside a wardrobe or fixed joinery;
• close to an AC drain or plumbing route;
• at a floor joint or skirting.

The height and timing matter. A mark at the base of a wall does not automatically prove capillary rise. A ceiling stain does not automatically prove that the entry point sits directly above it.

Do not erase the sequence

Avoid immediate cosmetic repair. Before repainting, resealing or cutting open a wall, retain:

• the event record;
• photographs with room and orientation;
• affected materials;
• visible water path;
• relevant roof, terrace, bathroom or landscape condition;
• recent contractor work;
• previous repairs;
• weather relation.

A targeted temporary measure may be needed to limit damage. It should not destroy the evidence required to understand the source.

What different observations may suggest

These are investigation prompts, not diagnoses.

Appears only during wind-driven rain

Review exposed walls, openings, façade joints, parapets and penetrations on the windward side.

Appears after rain has stopped

Review stored water, saturated assemblies, drainage backup and water travelling within cavities.

Appears during bathroom use but not rain

Review wet-room and plumbing routes before assuming an envelope problem.

Appears in a cooled room during humid weather

Review condensation, surface temperature, air leakage and AC operation as well as bulk-water sources.

Appears at lower walls throughout the year

Review ground moisture, lateral water, landscaping, plumbing and wall construction. Do not assume one cause from the stain pattern alone.

What the owner should request next

For a recurring or material condition, request a written investigation plan that states:

• the working hypotheses;
• the sequence of non-destructive checks;
• any controlled water testing;
• areas to isolate;
• conditions under which opening-up is justified;
• how repairs will be tested;
• how performance will be observed during the next comparable rain event.

Reality Check

Drying is not the same as resolution.

If the mark disappears but the water path remains, the next rain event starts the same sequence again.