Leaking Windows in Rain: Causes and Fixes

Window frame leaking: record the first wet spot

Start with a wide photograph of the opening from indoors. Then photograph the first place water appears: top corner, side, bottom track, sill or adjacent wall. Include the date and the conditions outside. A picture of a full wet sill after an hour is less useful than knowing where the first drops formed.

Use a short record: room, floor, window, time rain started, time water appeared, wind direction and affected finishes. Note whether the window was closed and latched. If the leak follows recent work, include what was done and when, without removing trims or seals yourself.

For high windows, take photographs from inside or from the ground. Our high rise glazing service provides a route for discussing difficult access as well as the affected glazing.

Window leaking when it rains or condensation?

Water that arrives during rain, particularly at one corner or along a joint, is a useful clue to external entry. Moisture on the inside face of the glass may have a different source. Note the timing, surface and pattern instead of deciding from the presence of water alone.

These observations help direct the investigation. They do not require you to take the window apart or reach outside an elevated opening.

Seals, drainage and flashings have different jobs

A weather seal around an opening, a drainage route within a frame and a flashing above it are parts of a system. A visible gap may need attention, but sealing every opening can interfere with drainage. Avoid filling frame slots or covering an unidentified gap before its purpose is clear.

The investigation should consider the window perimeter, opening joints and adjacent cladding. Water may arrive from a detail above the window and show up at the frame. This is particularly relevant where a roof-to-wall junction or balcony sits overhead.

If the concern is part of a larger building leak, our leak investigation and remediation service explains how we approach roof, facade and window interfaces together.

Why wind and heavy rain change the pattern

Wind can drive rain against the exposed face of an opening, while a longer downpour gives water more time to collect in a restricted drainage path. Compare the affected window with a sheltered opening: record which face of the building is wet, whether the track fills before the sill wets and whether the upper corner starts dripping first.

For example, a bottom track that fills before spilling indoors points the investigation towards drainage as well as seals. A drip at the head of the frame while the track remains clear calls for attention above the opening. These are clues to test, rather than reasons to seal the nearest visible gap.

What you can do before a visit

1. Keep the area around the wet opening accessible and move belongings where safe.
2. Wipe up accessible water and photograph staining before redecorating.
3. Record the first entry point during the next rain event from a safe indoor position.
4. Gather window installation records, previous repair invoices and any leak report.
5. Tell the contractor about water near electrical fittings, loose glass or unsafe finishes promptly.

Leave elevated work, dismantling and hose testing to the assessment. Uncontrolled spraying may send water into details in a way that makes the original cause harder to identify. In a rented or managed building, notify the owner or manager so access and the repair enquiry can be coordinated.

Resealing or a wider repair?

A local failed perimeter seal may call for removal of the failed material, preparation and a compatible replacement detail. A frame drainage issue, missing flashing or deteriorated adjoining material needs a different scope. Ask what evidence supports the proposed repair and which part of the water path it addresses.

Compare proposals by the junctions included, access equipment, preparation, materials, making good and checking. A quote to apply sealant is not the same scope as opening and rebuilding a defective junction. Record any work that remains outside the agreed repair.

If a leaking balcony sits above the window, mention it in the same enquiry. If the outside coating is affected, the exterior paint bubbling guide helps you separate coating preparation from unresolved moisture entry.

Keep a record after the repair

Retain the repair description and photographs, then compare the opening during similar weather. Note whether the original entry point stays dry and report any new pattern. Internal staining may need its own drying and making-good plan after the source has been dealt with.

For insurance questions, ask your insurer what evidence and approvals they require. Supply the leak timeline and contractor findings, and keep coverage decisions separate from deciding which repair the building needs.