Dampness in Buildings Causes of Dampness in Buildings
Dampness in Buildings Causes of Dampness in Buildings Remedial measures
Topics • Definitions • Causes of Dampness • Effects of Dampness • Remedial measures • Classification of Damp proofing material
Definitions • Dampness – The excess entry or penetration of moisture inside a building through its – Floors – Walls and – Roofs is called Dampness is dangerous both for Inmates Building • Due to dampness the building become unhygienic. • Dampness in buildings is a risk factor for health effects.
Dampness in buildings is a risk factor for health effects Associations found with cough, asthma, tiredness, airway infection – Increased relative risk 1. 4 -2. 2
Definitions • Peeling off – This term is related to plaster and it means that the plaster surface gets disfigured. • Blistered and Bleached – These term are related to Painting • DPC (Damp proof course) – It is a continuous layer of impervious material between source of dampness and building component
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Causes of Dampness • Following are the main causes of dampness in a building 1. 2. 3. 4. 5. 6. 7. 8. Rain penetration Level of site Drainability of the Soil Climatic conditions Defective Orientation Entraped moisture in the building Defective construction material Defective construstion
Causes of Dampness 1. Rain penetration • It is the main source of dampness. Heavy rain of short duration is less dangerous. rain water enters through joints, cracks and porous bricks or stones. 2. Level of site • Low laying building sites are effected by the depositing surface water and underground water. 3. Drainability of the Soil • Course grained soils like Sandy or gravely soils provides good drainibility conditions and fine grained soils like clay retain water and cause dampness.
Causes of Dampness 4. Climatic conditions • In cold climatic condition dampness causes due to condensation of water vapors. 5. Defective Orientation • If building is exposed to direct rain showers and less sun rays then it cause dampness. 6. Entrapped moisture in the building • Due to over soaked bricks and use of salty or alkaline water results dampness in building.
Causes of Dampness 7. Defective construction material • Porous bricks, soft stones, alkaline water etc. cause dampness of building. 8. Defective construction • Through defective joints of parapet, copping and masonry joints moisture can enter in the building. 9. Moisture originates in the building. • It is due to the leakage through water supply or sanitary system of building.
Effects of Dampness • Following are the harmful effects of dampness in buildings. – Building become esthetically poor. – It causes dry Rot to the wooden members provided in the building. – It cause corrosion of metals used in building. – Plaster peels off. – Paint blistered and bleached and the surface disfigured. – Holes and pits are formed in topping of floors. – Efflorescence occurs and bricks disintegrate and turn in to powder. – Un hygienic conditions in building.
Remedial Measures • By Damp Proofing Courses (DPC) • By surface treatment • By water proofing construction • By special devices/techniques
By Damp Proofing Courses DPC
Classification of Damp proofing material • Flexible Materials • Material which do not crack and deform due to loadings. – – Bitumen Mastic (Mastic Asphalt) Bitumen felt Hot Bitumen Metal Sheets • Rigid Materials • Materials that cannot resist transverse stresses. – – Rich Concrete Mortar Bricks Stone Slabs
Flexible Materials – Bitumen Mastic (Mastic Asphalt) • Hot Bitumen or Asphalt + Sand • Applied in hot state in 1” to 2” (2 cm to 5 cm) – Bitumen felt • 6 mm thick bitumen sheet available in roll form – Hot Bitumen • It is sprayed at @ 1. 75 kg/m 2 – Metal Sheets – Lead, copper, Aluminum sheets can be used • Lead can react chemically with cement so should be laid in lime mortar. • Minimum thickness of copper sheets should be 3 mm.
Rigid Materials – Rich Concrete • 1” to 2 -1/2” thick layer of P. C. C (1: 2: 4) painted with hot bitumen is applied – Mortar • Rich cement mortar CS(1`: 3) is laid in ¾” thickness (2 cm) as vertical DPC. • Painted with bitumen – Bricks • Over burnt bricks are used in two layers in CS(1: 3) mortar – Stone Slabs • Two layers of stone slabs in lime, cement and sand mortar (1: 1: 6) is provided in areas where stone is easily available.
Qualities of a good Damp proofing Material 1. Impervious 2. Durable 3. Non disintegratable 4. Stable under the loading 5. Level finish 6. Full coverage of wall thickness 7. Availability 8. Economical
Important places for Damp proofing materials • At Plinth Level (in walls ) (external & Internal) • Parapet walls • Window sill • Basements and Under ground Floors
Difference of Bitumen and Asphalt • Bitumen can be found in Nature. • Asphalt is a manufactured product, produced by refining crude oil by heating at 300 o. C in a distillation column. • Naphthene base crude oils are suitable
Naphthene base crude oils • Crude oil containing asphaltic materials but very little or no paraffin wax. This type of oil is suitable for making gasoline, lubricating oil and asphalt. It is also called asphalt-base crude.
Practical Advice for Reducing Excessive Moisture • • Fix roof and plumbing leaks right away Check for standing water (e. g. , basement) Make sure rain drains away from house (& irrigation) Ensure adequate ventilation (from outside) and circulation (inside). Use fans that vent air to the outside when bathing, showering, and cooking • After flooding, remove any wet or damp material right away and start drying (with fans). Pull up carpets.
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