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25 CAUSES OF DAMP IN THE HOME
Defects in roof coverings Defects in flashing Defects in valley gutters Unsuitable roof design, like inadequate roof overhang Absence of gutters and downpipes Condensation caused due to an absence of air-bricks Inadequate drainage Bad tiling or paving Cracks in floors, leaking balconies and walkways Insufficient load bearing of lintels Rising damp through a failed damp proof course (DPC) Downpipes leaking inside of columns Plumbing leaks in bathrooms and kitchens, leaking pipes and leaking geysers Tops of walls and parapets not sealed Inadequate roof timbers Unit built on rock slope Site generally
No rainwater  management in  complexes designed  for arid semi­desert  climates

Developers believe that air­bricks are  unnecessary and spoil the look of a Tuscan  Villa.  The indoor climate in many new  developments is damp and musty.  Louvred   windows can be used instead of air­bricks.

Modern developments have no gutters and  downpipes.  Rainwater runs down walls and  pools at the base of the structure.  It causes  penetrating dampness through walls and  around windows.

Gardens, sprinklers and water features laid against house walls

Water pooling on flat rooftops damages the structure

Weak plaster caused by insufficient cement or bad sand

No expansion joints or control joints, movement and subsidence causing cracks

Outlets discharging against the building create damp problems

Inadequate foundations on clay with high water table –  piled raft foundations necessary

Defects in pitched roofs Often builders neglect to place plastic sheeting under the roof covering. In the case of tiles, inadequately mortared ridge capping or broken tiles allow water penetration into the ceiling, which eventually causes the ceiling to disintegrate. Defects in flat roofs If a flat roof is not laid to fall to outlets, or if outlets are too small or too high, water eventually causes a breakdown of the waterproofing covering. The roof waterproofing is sometimes not properly done and lack of preparation of the surface or non-compliance with the manufacturer's specifications can cause damp penetration through the roof. Parapets and tops of walls must be coped or sealed to prevent damp penetration.

Defects in flashing Where roofs meet with parapets or other walls, proper flashing is essential. There should be under and cover flashing. Faulty gutters and downpipes If the gutters and downpipes are inadequate, or if the roof does not overhang the gutters and is not sealed, water builds up in the gutters and overflows into the roof cavity. Defects in valley gutters If the valley gutters under the tile intersections are too shallow, if the tiles have been hacked instead of neatly cut to a line, or the valley gutters become blocked., water overflows into the roof cavity. Damp penetrating through walls The use of poor quality porous bricks, plaster with insufficient cement, inferior paint, or inadequate surface preparation prior to painting can result in a breakdown of the surface and damp penetration. Damp penetrating around windows Windows should be sealed with silicon and there should be a damp-proof course under the windowsill. Plumbing leaks in bathrooms and kitchen These may only become evident when damp appears on the ceilings below. Bridged damp-proof course. If the ground or paving level is raised above the level of the damp-proof course, rising damp will result. A cause of damp often overlooked is through brickwork. This occurs if the plaster is soft and the brick joints are not property filled. Damp usually penetrates through the mortar and not through the bricks. An adequate roof overhang prevents soft continuous rain accompanied by light winds from precipitating against the walls. Not only does water deface the interior wall finish, but it can also weaken the thermal properties of the wall. Changing rainfall patterns caused by climate change may also create damp problems in buildings that previously had no signs of damp.

Copyright © 2010

Dampproofing & Waterproofing Association of South Africa

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