In there a brown stain?

Typically a brown stain results from water passing through a brick or over timber and is caused by:

  1. penetrating damp or
  2. a leak.

However, brown stains could be:

  • old and never painted over,
  • caused by rust, such as plasterer beading,
  • caused by condensation acting as a leak, 
    – such as insterstial condensation from a poorly ventilated loft.
Next steps

Check for penetrating damp >

Check for a leak >

Check for metal >

Check potential for interstitial condensation >

Where is damp located?

If it is exclusively at the base of a wall > check profile

If there is damp high up a wall or on another floor >

What is the profile of damp?

Is there a horizontal band of damp

Can you smell damp, or see mould?

Human don’t smell water. We smell mould which we associate with dampness. We sense humidity, such as when it is “close”.

When there is mould go to the next step>

Check the ventilation is working?

If you have an anemometer (windspeed tester) test the airspeed exiting the building from the bathroom, kitchen and other wet rooms.

Consider the need for ventilation in the property overall.

Has the property been damp proofed?

Find out if the property has been damp-proofed.
(Often there are tell-tale drill holes on the outside). 

If it has then walls may not reveal the event of dampness.

Are there signs of condensation?

Look for dribble marks on external walls and or windows, or window sill.

Compare data logger out put?

Data logger monitoring changes in relative humidity over time is useful for identifying condensation and mould risks, and ventilation issues.

Is there high relative humidity in the sub-floor void?

Common causes of rising damp like symptoms

There are damp patches on the rear wall. They look like hygroscopic salts. Stains are from penetrating damp.
Damp patches despite no recent rain.
Around the edges of the damp proofed wall, there are signs of brown staining.
Damp on wall, which has been damp proofed.