Damp / mould / condensation / mould
Why is mould growing around my windows?
Start with the observable symptom. This page explains possible causes; it is not a diagnosis. It covers both “mould” and “mold” wording for the same intent.
Mould around a window often follows repeated condensation on the glass, frame or reveal, but it can also indicate a failed seal or water entering from outside. Clean only a small hard-surface spot safely and address the moisture source so it does not return.
Start with the pattern.
Dark or coloured mould appears on the frame, sealant, sill or wall around a window.
Possible causes, not a diagnosis.
- Condensation is repeatedly wetting the coldest parts of the window area.
- A failed seal, cracked joint or blocked external drainage is allowing water in.
- Cold bridging or poor ventilation is keeping the reveal damp.
Check what is safe to observe.
- 01
Map the mould location and photograph it before cleaning.
- 02
Check whether the area is wet after rain or mainly after sleeping and bathing.
- 03
Look for damaged sealant, soft plaster, staining or mould between double-glazed panes.
Take the smallest useful step.
- For a small hard-surface spot, use an appropriate mould product exactly as labelled and ventilate.
- Dry the frame and improve normal ventilation.
- Keep a record if the mould returns or expands.
- Do not dry-brush a large mould area or mix cleaning products.
- Do not paint over mould before the cause and surface are dry.
- Ask a landlord or housing provider to investigate recurring mould and repair defects promptly.
- Use qualified help for extensive mould, porous materials, water ingress or health concerns.
Professional requirements and rental responsibilities vary by location. Use the qualified local professional or housing authority that applies where you live.
UK example: GOV.UK repairs guidanceWhy this page says that.
This page separates an observable symptom from possible causes and keeps the recommended action within a safe household boundary.