This section lists common sources of moisture ingress that can be found in buildings during specialist damp proofing surveys. Any one of these sources can result in the finding of “damp” during general building surveys. The source of moisture should be correctly identified before any remedial damp proofing measures are undertaken.
Condensation occurs when air with a high water vapour content comes into contact with cool surfaces (below dew point temperature). The water condenses from the air, resulting in the formation of water droplets on the cold surfaces. Excessive condensation can lead to the rotting of window sills, dampness on walls, and mould growth. The presence of black spot mould on walls is an indication of excessive condensation.
Reducing the moisture loading in the air and/or improving the ventilation is the most effective method of dealing with condensation. Dehumidifiers are costly to run, require emptying and should only be considered as a temporary measure. Dehumidifiers and anti condensation paints just treat the effects and do not remove the cause. Whole home ventilation systems are a cost effective method of dealing with the cause of condensation and removing the effects.
The ingress of water into a building as a result of a building defect such as:
- Blocked or broken guttering
- Blocked or broken downpipes
- Defective external rendering or pointing
- Defective weatherproof seals on doors and windows
- No weatherboard on doors
- Bridged wall cavity
- Roofing defects such as loose or missing tiles/slates, damaged or missing flashings, or damaged coping.
- Overflow pipe continuous running
- Lack of drip beading on rendered walls or blocked drip grooves on cills
- Porous or cracked bricks
The movement of moisture through materials by capillary action
- Absence of physical Damp proof course (DPC) or damp proof membrane (DPM)
- Breakdown or failure of physical Damp Proof Course
- Ineffective chemical damp proofing or replastering
- Bridging of damp proof course by increase external ground levels, external render, internal solid floors, blocked cavity
Internal building defect or other source
The ingress of water through the failure of a water carrying appliance, the spillage of water or other source of moisture
- Plumbing faults such as leaking valves, leaking radiators, hot water tank, washing machines or waste pipes.
- Bath or shower overflow or splashing
- Condensation on un-insulated cold water pipes.
- Lack of adequate roof space ventilation leading to condensation and causing mould growth
- Blocked up fireplaces causing condensation to form in the void.