Damp / mould / condensation / condensation
Why is condensation forming on my walls?
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.
Condensation on a wall means moisture in the indoor air is reaching a surface cold enough for water to form. It is common behind furniture and at corners, but a persistent patch may also involve a leak, penetrating damp or a cold-bridging defect.
Start with the pattern.
A wall feels clammy or shows beads of water, usually at corners, behind furniture or near windows.
Possible causes, not a diagnosis.
- Indoor humidity is high and air is not circulating.
- The wall surface is unusually cold because of insulation, layout or a thermal bridge.
- Rainwater or a plumbing leak may be entering the wall if the patch follows weather or pipework.
Check what is safe to observe.
- 01
Move furniture slightly and compare the affected area with the rest of the wall.
- 02
Look for staining, flaking paint, salt deposits or a clear vertical path.
- 03
Check whether the patch changes after cooking, bathing or heavy rain.
Take the smallest useful step.
- Improve normal ventilation and keep air moving around the affected wall.
- Photograph and date the patch before cleaning or redecorating.
- Keep the room at a reasonable, steady temperature where possible.
- Do not dry a wet wall by covering it with wallpaper or impermeable paint.
- Do not drill into a damp patch without considering hidden pipes or cables.
- Ask a landlord or housing provider or building professional to investigate recurring or spreading damp.
- Get urgent help for a wet electrical fitting, active leak or substantial water damage.
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.