Dampness in Buildings
ALL THESE SOURCES OF WATER ARE UNWANTED!!
Visual Evidence of Dampness
• Mould growth
• Deterioration of finishes, blowing/disintegrating plasterwork
• Liquid water on surfaces
• Staining of finishes
• Efflorescent salts on surfaces
• Timber decay
• Distorted timbers
• Dampness to finishes
The most common cause of damp in domestic properties remains
How are problems damp diagnosed?
Correct diagnosis is vital!
Rising Damp Visual appraisal
Reproduced from BRE Digest 245 (2007) “Rising Damp in Walls: Diagnosis and Treatment
We could define rising damp as:
The vertical movement of water up through masonry, the water originating from ground water. The water rises through a series of interconnecting pores by a process called ‘capillarity’ – broadly, porous masonry acts like a ‘wick’.
Note: ‘Capillarity’ in building materials has nothing to do with or related to water rising in plants/trees. The rise of liquids from roots to leaves in plants is a process known as ‘cohesion’, not capillarity, and involves hydrogen bonding of water.
If the ‘suction’ of the wall is greater than the suction of the ground then water will rise – if not water will not rise
Salt concentration at top of rise ‘Salt band’ – most of the salts are hygroscopic
No significant/low salt levels at base!
Soluble chlorides, nitrates, sulphates and other mineral salts/soluble materials
Rainwater in the soil is the most prevalent source of water at the base of a wall – not water table
How do we treat Rising Damp?
Barriers to damp can take a number of forms. They all work using barriers to protect the internal finishes from water entering the building.
Measuring Dampness in Buildings
Electric moisture meter
• Non destructive – quick to use
• Easy to create “moisture profiles”
• Small and portable
• Valuable aid in the right hands
• Calibrated for use on wood – not masonry
• Can give misleading readings (e.g. contaminant salts, foil-backed paper, high carbon substrate)
• Often misused in the wrong hands
Moisture Analysis (Oven Dry Method)
The presence of Capillary/Free moisture in a material indicates a source of water ingress.
Damp Created Inside
The most common form of dampness in residential properties in the UK
Misdiagnosis & misunderstanding of condensation is common
It is widely accepted that we in the UK have a “condensation season”.
This is usually between October and April but is dependant on the outside temperature.
If there are significant dampness problems outside through the summer months, it is probably not condensation.
Condensation occurs when water changes from its ‘gaseous state’ to its ‘liquid state’.
This only happens when the air reaches a relative humidity of 100%
The point at which the water changes state as saturation occurs is known as the ‘Dew Point’.
Condensation is deposited on any surface that is below the Dew Point.
Condensation can be deposited at the surface and is known as ‘surface condensation’
Or within a structure where it is called ‘interstitial condensation’
Where is the water from?
Water from rising or penetrating damp is very unlikely to contribute significantly to a condensation problem.
If condensation is occurring the walls will be relatively cold. If the walls are cold then significant evaporation is unlikely.
Pascal (Pa) of kilo Pascal (kPa) is the standard unit for measuring pressure.
1 hectopascal (hPa) = 100 Pa ≡ 1 mbar.
1 kilopascal (kPa) = 1000 Pa ≡ 10 hPa ≡ 10 mbar.
Diagnosis and Investigation
Obvious evidence of condensation problems:
• Mould Growth on walls ceilings
• Musty Smell
• Fungal Growth
• Water droplets on impervious surfaces
• Steamed up windows
• Decay to internal sections of timber window frames
Water will not condense out of the air unless temperatures are at, or below, dew point.
Mould growth can occur if high humidity levels are maintained for long periods.
To determine if condensation is happening at the time of your investigation:
Air Temperature = Thermometer
Humidity = Hygrometer
Dew Point = Calculation
Surface Temperatures = Surface Thermometer
A MMS meter can do all these things in real time
Data Logging stations
Other things to look for
• Construction types
• Placing of Insulation
• Vapour proof materials within construction
• Ventilation Systems – condition & serviceability
• Evidence of the causes of atmospheric water