COMMON DAMP PROBLEMS
The lack of adequate waterproofing poses a very real threat to the structural integrity of homes and buildings. Needless to say, it poses a very real threat to their contents as well. Damp homes and buildings also pose a threat to the health of its occupants. It is unsightly and a constant source of annoyance. The purpose of waterproofing therefore 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 prevent or remedy them, saving you great expense, time and aggravation.
Rising damp occurs as a result of capillary suction of moisture from the ground into porous masonry building materials such as stone, brick, earth and mortar. It potentially occurs where there is no damp proof course (DPC) or where the DPC has been damaged or bridged. The height to which the moisture will rise is determined by the evaporation rate and the nature of the wall. The normal limit for rising damp generally ranges from 0.5 to 1.5 meters above ground level. Rising damp may show as a stain on wallpaper and other interior finishes, blistering of paint and loss of plaster. Damp walls encourage the growth of mould, which with high humidity can lead to health problems for occupants. Externally, a damp zone may be evident at the base of walls and in extreme situations, with associated fretting and crumbling of the substrate.
Falling damp is caused by downward water penetration from the top of porous masonry walls. This could be as a result of the top of a boundary wall (coping) not being adequately waterproofed, failed flashings, blocked or leaking gutters, joints that have lost their mortar and the build-up of dirt and moss on upper surfaces of stone or brickwork. Fallen leaves, bird manure, moss and dirt contain weak acids and salts, which if carried by water into masonry can promote decay.
Penetrating damp is a common form of damp. It occurs as a result of the horizontal ingress of water through gaps (sometimes tiny) in a building's substrate. Penetrating or horizontal damp can be due to leaking water pipes and unprotected plaster or brick. Air-conditioning drips and hot water system overflows can also cause problems. Penetrating damp tends to produce localised patches of dampness and decay, whereas rising damp may affect the base of a whole building.
Efflorescence is where an appreciable quantity of soluble salts is present in the masonry. It routinely occurs in masonry construction, particularly in brick and typically occurs during the initial curing of the cementitious product. Damp carries these salts up the masonry to where the damp evaporates. As the water evaporates, it leaves the salts behind as a white fluffy deposit. This deposit can normally be brushed off when dry. It usually disappears with time after rains or washing with water. Efflorescence is generally an aesthetic concern and not a structural one. However, where there is excessive efflorescence, the crystallizing salts within the pores of the masonry can disrupt even the strongest material, leading to the fretting and crumbling of the substrate.
Positive Side Waterproofing
Positive side waterproofing prevents damp problems at its source whereas negative side waterproofing is a remedial solution only. Positive side waterproofing is applied to the outside surface of a building or structure - usually to the external walls. Positive side waterproofing is also applied to the walls of showers, bathrooms, kitchens and laundries to prevent moisture penetration into adjoining rooms and cupboards. In these instances, they are the wet side of the wall. Positive side waterproofing protects against, amongst others, corrosive soils which can attack masonry and concrete and even steel reinforcing. Water seepage as a result of a high water table, rain and even garden sprinklers is also prevented. In all new construction, positive side waterproofing must form an integral part of the building specification in order to ensure a problem free structure.
Negative Side Waterproofing
The most common use of negative side waterproofing is where access to the outside face is inaccessible or where the source of the problem is impossible or difficult to reach. Examples include pits, shafts, basements, wine cellars, underground parking and retaining walls etc. Shells of ponds and pools are also susceptible to negative water seepage. Negative side waterproofing is generally a testament to poor building practices. Negative side waterproofing materials can also be applied to the positive side of a building. Membrane waterproofing systems are not suitable for negative side waterproofing as the external water pressure (hydrostatic pressure) can easily disbond the membrane from the substrate.