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Dampness in Buildings Causes

Dampness is the presence of hygroscopic moisture in thebuildings. Ground water contains soluble salts, the most significant of whichare chlorides, nitrates and sulphates. When dampness occurs, these pass withthe water up the wall and are left behind when the water evaporates. Over manyyears of active dampness, large quantities of these salts accumulate within themasonry and decorative surface,

 most becoming concentrated in a general ‘saltband’. Both chlorides and nitrates are usually hygroscopic, (i.e. they canabsorb moisture from the surrounding environment) and, in general, the greaterthe amount of salts the greater the absorption of moisture – especially underhumid conditions. 
 It leads to unhygienic conditions affecting badly thehealth and comfort of the inhabitants and deteriorating the buildings.Protection against dampness should form an essential feature for any type ofconstruction.
Sources of Dampness
The sources which create dampness in buildings are 

a.   
Geological and climatic conditions
  • Rain penetration
  • Ground moisture rise
  • Condensation in buildings due to moisture in the atmosphere
  • Drainage of the site
  • Orientation of the buildings
b. Structural causes
  • Water used during construction
  • Defective construction


Effects of Dampness: 
Dampness tends tocause secondary damage to a building. The unwanted moisture enables the growthof various fungi in wood, causing rot. Plaster and paint deteriorate andwallpaper loosens. Stains, from the water, salts and from mould, mar surfaces.Floor coverings loose their bond with floor bases. 
Externally, mortar maycrumble and salt stains may appear on the walls. Steel and iron fasteners rust.Electrical installations get damaged. It may also cause respiratory illness tothe occupants. In extreme cases, mortar or plaster may fall away from theaffected wall. 

Dampness in buildings can generally be divided into three main catagories, eachcaused by a different phenominum. The categories are rising damp, penetratingdamp and condensation. 
Dampness is a major source of disrepair in a building and can be caused byseveral factors such as 
  • Leaking pipes or overflows
  • Rain seeping through the roof, spilling from a blocked gutter, seeping in around windows
  • Rising damp due to a defective damp proof course or missing damp proof course
  • Condensation where moisture in the air condenses onto cold surfaces