Dampness in Buildings Causes

Dampness is the presence of hygroscopic moisture in the buildings. Ground water contains soluble salts, the most significant of which are chlorides, nitrates and sulphates. When dampness occurs, these pass with the water up the wall and are left behind when the water evaporates. Over many years of active dampness, large quantities of these salts accumulate within the masonry and decorative surface,

 most becoming concentrated in a general 'salt band'. Both chlorides and nitrates are usually hygroscopic, (i.e. they can absorb moisture from the surrounding environment) and, in general, the greater the amount of salts the greater the absorption of moisture - especially under humid conditions. 

 It leads to unhygienic conditions affecting badly the health and comfort of the inhabitants and deteriorating the buildings. Protection against dampness should form an essential feature for any type of construction.
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 to cause secondary damage to a building. The unwanted moisture enables the growth of various fungi in wood, causing rot. Plaster and paint deteriorate and wallpaper loosens. Stains, from the water, salts and from mould, mar surfaces. Floor coverings loose their bond with floor bases. 

Externally, mortar may crumble and salt stains may appear on the walls. Steel and iron fasteners rust. Electrical installations get damaged. It may also cause respiratory illness to the occupants. In extreme cases, mortar or plaster may fall away from the affected wall. 

Dampness in buildings can generally be divided into three main catagories, each caused by a different phenominum. The categories are rising damp, penetrating damp and condensation. 
Dampness is a major source of disrepair in a building and can be caused by several 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