AN ANALYSIS OF THE CAUSES, PREVENTION AND TREATMENT OF DAMPNESS IN BUILDINGS (A CASE STUDY OF MAKOKO, LAGOS STATE)
Dampness can be defined as water penetration through the walls and certain elements of a building (Halim et al., 2012). Dampness can also be defined as an excessive quantity of moisture contained in building materials and components which causes adverse movements or deterioration and results in unacceptable internal environmental conditions (Briffet, 1994).
Burkinshaw and Parrett (2004) defined dampness as the amount of moisture content present in a material and can be classified as capillary moisture content, equilibrium moisture content, hygroscopic moisture content, total moisture content and potential moisture content. Dampness is the most frequent and main problem in buildings and contributes more than 50% of all known building failures (Halim et al., 2012; Trotman, 2004).
According to Hollis (2000), dampness is inextricably linked to most building deterioration. A source of water close to a building will also be one of the problems associated with dampness. These problems include symptoms such as dirty spots on the building, biological plants like the growth of fungi, mosses and creeping plants, paint flaking, blistering etc. (Halim et al., 2012). In order to successfully diagnose and make appropriate recommendations for remedial actions, one should understand dampness and its impact on buildings.
The ultimate objective of any dampness study is to identify the lead source of moisture in order to recommend actions to remedy the problem (Halim et al., 2012). According to Hollis (2000), sources of dampness can be classified as rising dampness, penetrating dampness, condensation and pipe leakages. According to Burkinshaw and Parrett (2004), dampness can be classified as air moisture condensation, penetrating dampness, internal plumbing leaks, below ground moisture or building specific sources.
Rising dampness occurs as a result of capillary suction of moisture from the ground into porous masonry building materials such as stone, brick, blocks, earth and mortar (Halim & Halim, 2010; Ahmed & Rahman, 2010; Riley & Cotgrave, 2005; Trotman et al., 2004; New South Wales Heritage Office, NSWHO, 2005). The moisture evaporates from either face of the wall (inside or outside), allowing more to be drawn from below. The height to which the moisture will rise is determined by the evaporation rate and the nature of the wall (Halim & Halim, 2010; Ahmed & Rahman, 2010; Trotman et al., 2004; Riley & Cotgrave, 2005; NSWHO, 2005). The normal limit for rising dampness ranges from 0.5 m to 1.5 m above ground level (Halim & Halim, 2010; Ahmed & Rahman, 2010; Trotman et al., 2004; Riley & Cotgrave, 2005; NSWHO, 2005). Rising dampness may show as a high-tide-like stain on wall paper and other interior finishes, and, when it is severe, as blistering of paint and loss of plaster. Damp walls encourage the growth of mold which in conjunction with high humidity, can lead to health problems to occupants (Halim & Halim, 2010; Ahmed & Rahman, 2010; Trotman et al., 2004; Riley & Cotgrave, 2005; NSWHO, 2005).
Water penetration through a building enclosure depends on the simultaneous occurrence of three things: the presence of water; an opening through which water can enter and a physical force to move the water (Beall, 2000). Water can be present as rain, melting snow and soil moisture. Several forces such as gravity, air currents, capillary suction, surface tension, kinetic energy, air pressure and hydrostatic pressure influence the penetration of water into buildings (Beall, 2000). Drips from air conditioning or hot water system overflows, rain water, pipe leakages, water from horizontal directions, etc. can also cause penetration dampness in buildings (NSWHO, 2005). These sources tend to produce small, localized patches of dampness and decay, whereas rising dampness may affect the base of a whole building (NSWHO, 2005).
According to Curtis (2007), dampness resulting from condensation occurs where water in the air inside a building condenses on a cooler surface. This is usually indicative of cold spots in the building, sometimes called cold bridges (Curtis, 2007). It can also occur where there is poor ventilation or where short intense heating cycles do not allow the walls to fully warm up (Curtis, 2007). This situation allows the heated air to hold more water, which condenses when the temperature drops (Curtis, 2007). Excessive condensation frequently results in severe mould growth which can in turn create health hazards. Condensation is one of the most common forms of dampness in residential buildings, mainly caused by warm moist air formed from cooking, washing, bathing or even by just breathing, condensing onto colder surfaces in the homes (Burns, 2010). Damp patches can appear on plaster walls in odd places, particularly on outside walls, often appearing and disappearing on a regular basis (Burns, 2010). Condensation is mostly accompanied by mold which is black in colour but can virtually be of any colour and is very common on walls and ceiling, underneath bay windows, etc. (Burns, 2010). According to the British Research Establishment (BRE), 80-85% of dampness problems in the United Kingdom arise due to condensation or manmade moisture (Ryan, 2002).
There are many visual signs to look out for when diagnosing any damp situation (South Northamptonshire Council, SNC, 2012). In Denmark, rising dampness in the walls of buildings is associated with symptoms such as salt efflorescence, deterioration of rendering and plastering mortar, deterioration of wooden parts of buildings, etc. Condensation is associated with mold growth, usually on top of walls and ceilings (Burns, 2010). Rising dampness may show as a high-tide-like stain on wall paper and other interior finishes, and, when it is severe, as blistering of paint and loss of plaster (Halim & Halim, 2010; Ahmed & Rahman, 2010; Burns, 2010; Curtis, 2007; Trotman et al., 2004; Riley & Cotgrave, 2005; NSWHO, 2005). Mold growth may also be associated with rising and penetration dampness in buildings (Burns, 2010). The 1991 House Condition Survey found that 10.4million homes were affected by mold growth (Ryan, 2002; Wheeler & Critchley, 1998) and the Northern Ireland House Condition Survey in 1996 also found that 16% of homes experienced some form of mold growth (Ryan, 2002).