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What are you seeing?

Condensation

Condensation is liquid water forming when humid indoor air meets a cold surface. Timing is often the strongest clue.

Diagnose this symptomCompare likely causes
Recognise the pattern

Does your condensation look like this?

Use several clues together. A single stain or reading rarely proves the cause.

01Water droplets on glazing
02Worse overnight or in the morning
03Common after showers, cooking or drying clothes
What could be behind it?

Compare the most likely cause families

The same visible symptom can have very different causes. Look for the clue that best fits timing and location.

Explore all problems
1

High indoor humidity

Compare this possibility with weather, room use, height and any nearby services before acting.

2

Insufficient extraction or background ventilation

Compare this possibility with weather, room use, height and any nearby services before acting.

3

Cold surfaces or thermal bridging

Compare this possibility with weather, room use, height and any nearby services before acting.

Do this before buying a fix

Three useful checks

1
Measure relative humidityAdd the result to the overall pattern rather than treating it as proof on its own.
2
Test bathroom/kitchen extractorsAdd the result to the overall pattern rather than treating it as proof on its own.
3
Track when droplets appearAdd the result to the overall pattern rather than treating it as proof on its own.
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DampDeck symptom guide

Condensation: what to know

What it can mean

Water droplets on the room side of glass or other cold surfaces point strongly toward humid indoor air meeting a cold surface.

Three useful questions

  • Is it mostly mornings or colder weather?
  • Is extraction working after showers/cooking?
  • What does a hygrometer show over time?

Do not choose treatment from the symptom alone

The same visible symptom can come from different moisture sources. Use timing, position and nearby building/plumbing details to narrow it down.

Evidence & reviewDampDeck reviewed this guidance on 3 September 2026. UK government guidance says damp and mould should be addressed by identifying and correcting the underlying moisture cause; surface mould removal alone does not prevent recurrence.UK Government source →
Continue the diagnosis

Related DampDeck guides

CondensationMoist indoor air forming water on colder surfaces — often windows, external walls and cold corners.Read next →VentilationRemoves moisture-laden air and is often central to condensation control.Read next →
Investigate before treating

Three questions that narrow it down

1

Is it mostly mornings or colder weather?

2

Is extraction working after showers/cooking?

3

What does a hygrometer show over time?

What can sit behind this symptom

Compare the likely moisture routes

The symptom tells you where to look. Timing and building context help identify why it is happening.

Condensation & humidityPossible causeCondensation & humidityMore likely when the surface is cold and the pattern is seasonal.Explore →Rain penetrationPossible causeRain penetrationMore likely when the patch changes during or after wet weather.Explore →Plumbing leakPossible causePlumbing leakMore likely around water services or where the weather makes no difference.Explore →
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Useful products for this stage

Only products that support the investigation or an appropriate fix are shown here. An active leak or building defect still needs repairing.

Digital hygrometerRelevant productDigital hygrometerBrowse on Amazon →Building moisture meterRelevant productBuilding moisture meterBrowse on Amazon →Protective cleaning glovesRelevant productProtective cleaning glovesBrowse on Amazon →
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Useful products for checking or controlling the conditions

Products can help measure, ventilate, dry or clean. They should not be presented as a substitute for fixing an active leak or building defect.

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Relevant to Condensation

Humidity & monitoring

DampDeck only surfaces products that make sense for this stage of the investigation. Products do not replace diagnosis or repair of an active leak.

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Professional help

Find the right specialist once the likely cause is clearer.

Search locally by town or postcode instead of choosing a treatment from the symptom alone.

Find local specialists