3-dampness In Buildings.ppt 1u1m1b

DAMPNESS IN BUILDINGS (Causes & 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 o Floors o Walls and o Roofs is called Dampness.  Dampness is dangerous both for o Inmates o Building  Due to dampness the building become unhygienic.  Dampness in buildings is a risk factor for health effects.

DEFINITIONS • PEELING OFF – This term is related to plaster and it means that the plaster surface get 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

CAUSES OF DAMPNESS • Following are the main causes of dampness in a building

1. 2. 3. 4. 5. 6. 7. 8. 9.

Rain penetration Level of site Permeability of the Soil Climatic conditions Defective Orientation Entrapped moisture in the building Defective construction material Defective construction Moisture originates in the building.

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 ts, cracks and porous bricks or stones. 1. LEVEL OF SITE Low laying building sites are effected by the depositing surface water and underground water. 1. PERMEABILITY OF THE SOIL Course grained soils like Sandy or gravely soils provides good permeability conditions and fine grained soils like clay retain water and cause dampness.

Causes of Dampness 2. Climatic conditions • In cold climatic condition dampness causes due to condensation of water vapors.

3. Defective Orientation • If building is exposed to direct rain showers and less sun rays then it cause dampness.

4. Entrapped moisture in the building 1. 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 ts of parapet,

copping and masonry ts 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 cause dry Rot to the wooden 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

Damp proofing material • Classification of Damp proofing

material • Qualities of a good Damp proofing Material • Important places for Damp proofing materials.

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/m2 – 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 or fat cement mortar CS(!: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

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Dampness in buildings is a risk factor for Associations found with cough, health effects asthma, tiredness, airway infection

– Increased relative risk 1.4-2.2

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Typical section of Wall

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DPC at different locations 3- At Window Sills 1- At Plinth Level 4- Basements & Under Ground Floors

2- At Parapet Walls

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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 oC in a distillation column.

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) Vent clothes dryer to the outside 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. * Mold in My Home: What Do I Do?, CHDS 2004