Understanding damp

Understanding damp

Damp damage to South African houses is one of the most worrisome conditions for estate agents and potential buyers or sellers.   A HouseCheck home inspector will usually be able to diagnose the cause of the damp and place the situation in a practical cost-context.    Like most problems, once the situation has been faced and understood, it usually becomes much more manageable and less frightening.

Here are the different types of damp which your home inspector may observe.

Penetrating damp

Penetrating damp is usually caused by roof leaks or water penetrating the structure via exterior wall cracks. Other causes may be leaking plumbing, a poorly waterproofed adjacent shower or bath, a planter on an external wall, or water penetrating  through the wall as a result of incorrect exterior ground levels.

Further investigation is usually recommended. Damaged areas should only be repaired and decorated once there is certainty that the source of the moisture ingress has been repaired.

Rising damp

Damp confined to lower parts of internal walls area usually rising damp. Rising damp is caused by ground water wicking up through the masonry due to the lack of, or compromised, damp proof course (DPC) – nowadays robust PVC plastic.   High exterior ground levels can also be the cause of water penetrating the wall above the DPC and manifesting in apparent rising damp (actually penetrating damp).

In all cases of rising damp, further investigation by a reputable waterproofing company is recommended.  Possible remedies include the installation of a physical or chemical damp proof barrier, or the re-grading of the exterior ground.

Conventional DPC was not available when many older South African homes were built. Often either malthoid (flexible bitumen-coated felt) or slate (a dense rock that splits easily into thin layers) was used to prevent rising damp in the walls of these old buildings.  However, both malthoid and slate can deteriorate  over many years, causing rising damp to become active and visible low down on the walls of many old structures.

Areas damaged by rising damp should not be redecorated until the cause of the rising damp has been identified and repaired.

Efflorescence

Efflorescence is a white, powdery substance that forms on the surfaces of concrete, bricks and plaster.  Efflorescence is caused by water soluble salts migrating through the masonry via capillary action. Once these soluble salts come into contact with air, unsightly white sediment appears.   On brick, concrete, or clay tile surfaces  efflorescence can be removed by washing with water and will not  keep appearing once the bricks, mortar, concrete and tiles in the wall have fully dried.  However, if the source of the efflorescence is water ingress (either penetrating or rising damp), then efflorescence is likely to continue manifesting until the cause of the water ingress has been resolved.

Condensation

Condensation occurs when moist, warm air – usually from a shower, bath or from people’s breath in a closed -up bedroom – contacts a colder surface and the water in the moist air condenses  –  causing the cold surface to become damp.   Condensation occurs in rooms with poor ventilation and is easily visible on glass surfaces (window panes and mirrors). But condensation also occurs on smooth ceilings and wall surfaces where mould (microscopic fungal spores) is often the result.  Mould can be extremely dangerous – especially to people with allergies.   Mould can normally be removed with a mild bleach solution.  To stop condensation re-occurring it is necessary to improve ventilation by leaving windows open or by installing extractor fans.

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