Exploring dampness

Water leak from pipes etc.

Profile of a leak from inside. Meter readings are high near the point of source and radiating out. The leak may affect external surfaces as well.

• Requires urgent work relatively quickly.
• Soaks walls from the point of source.
• Pipe leaks will keep walls damp in dry weather.
• Dangerous if left unattended.
• Sometimes accompanied by foul smells.
• Can have multiple sources.
• Complaints arise out of disputes between neighbours or contractors.
• Accomplices: the wick and the fence.
• Remedy principle: stop the cause of the leak.
• Can be mistaken for rising damp if the cause of the leak is from underground or low down.
• Not always easy to find the exact location of the leak.
• Will cause walls to become cold, and so cause condensation.

Penetrating damp

Profile of water penetration. Moisture arrives at the inner surface directly from outside. The control measure needs to come from another room. Check for presence of sulphates and carbonates and the absence of nitrates and chlorides.

• Likes continuous materials, such as solid walls and solid floors; also porous materials, like poor-quality bricks, mortars and soft stones.
• Needs a link from outside to inside, but does not always appear opposite the source.
• Needs time to percolate into the building.
• Hangs around in timber, making it comparatively damp and prone to rot.
• Looks for the easiest route to evaporate out of the structure and migrates to that area.
• Spreads gradually and saturates locally.
• Carries soluble contaminates like sulphates and carbonates.
• Dangerous if left unattended in still air conditions.
• Accomplices: The wick, the meter, the smoke screen.
• Remedy principle: rebalance the wall to allow it to cope, and give time for signs to diminish.
• Will cause walls to become cold and so cause condensation.
• Remedies applied in the wrong place will simply move the staining elsewhere, even if this takes several years to manifest.
• Can be mistaken for rising damp if the cause is low down the wall and wicking is prolific.

Condensation

• Water vapour held in the air.
• Mould will only grow on condensate or due to rainwater penetration.
• Causes mould marks in still areas like cupboards and behind furniture placed against walls.
• Needs cold(er) surfaces to form water –where surface temperatures are below the dew point temperature of the internal air (or in much warmer climates, below the external air).
• Does not contain contaminates.
• Likes kitchens and bathrooms, bedrooms and small flats.
• Gets everywhere and moves around the house.
• Likes cold homes where lots of moisture is created.
• Not usually present during an inspection.
• Can form inside walls and roofs.
• Reduces efficiency of insulation.
• Disappears as quickly as it forms.
• Makes all other damp causes worse.
• Disguises other causes.
• Not easy to monitor if the remedies are working.
• Dangerous (to susceptible people) if mould is left unchecked.
• Accomplices: the fence, the meter, the unreliable witness.
• Remedy principle: warm up cold surfaces and improve ventilation. Re-set the balance between the amount of moisture in the air and the air temperature.
• Can be overlooked when evaluating other causes, particularly on hot days.
• Can come back even after remedial works.
• Killing mould growth will not stop it forming, as the spores are everywhere.