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Damp police say stop there!

High moisture areas such as kitchens and bathrooms can be problematic once damp starts to surface. Here’s how to identify, prevent and fix damp problems


Damp problems usually occur due to the lack of adequate waterproofing, and can pose a very real threat to the structural integrity of homes and their contents. Damp homes and buildings pose a threat to the health of its occupants as well. Damp is also unsightly and a constant source of annoyance.

The purpose of waterproofing is to protect homes and buildings, as well as their contents, against the damaging effects of water. Waterproofing can therefore be defined as a material or system that prevents or resists moisture and water seepage through the masonry components of a home or building.


Having a little knowledge of the more common damp problems will help you to prevent or remedy them, saving you great expense, time and aggravation.


Why treat damp?

Damp is usually treated for purely cosmetic reasons, to remove the obvious symptoms that people can see and smell. However, even when damp is not visible, it would be foolish to ignore its presence, since its long-term effects are damaging and can be costly.


Your home is likely to be your largest investment. If left untreated, damp can cause structural and cosmetic problems that will adversely affect the value of this investment. The fungal attack often associated with damp can be extremely damaging, especially in older houses with suspended timber floors. In addition, damp timbers are known to be more susceptible to termite attack than dry timbers.


Health effects

Damp will make a building cold, because heat within the house is absorbed in driving the moisture from the walls. Living in cold and damp conditions is known to exacerbate certain medical conditions such as bronchitis. Where the damp has caused fungi, bronchial problems can be compounded by fungal spores.


Causes of damp in the home

* Home developments

In general, developers sometimes believe that air bricks are unnecessary and spoil the look of a Tuscan villa. This causes the indoor climate in many new developments to become damp and musty. Louvered windows could be used instead of air bricks.


Also, many new and modern developments don’t have gutters and downpipes. Rainwater runs down walls and pools at the base of the structure.  This causes penetrating damp through walls and around windows.


Bad rainwater management in complexes with wrongly designed sprinkler systems and water features laid against house walls also cause problems. Another big problem is weak plaster caused by insufficient cement or bad sand, and this, together with a lack of expansion joints or control joints, can result in movement and subsidence that can cause cracks.


* 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 specific outlets, or if outlets are too small or too high, water eventually causes a breakdown of the waterproofing covering. The roof waterproofing is also 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 the top 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 silicone 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 falling 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.


In the next article about damp, we'll look at how to repair damage caused by damp.

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