What is Dampness? Causes, Effects and Preventive Measures.

What is Dampness?

Dampness is the absorption of unwanted moisture by the process of capillary action in the structure which is responsible for various defects in structure.


What are the various causes of dampness?

Moisture rising up the wall from bottom.

Due to capillary action the water travels from the soil to the walls & floors.

☛Rain water travelling from top wall.
If the top portion of wall is not treated against the penetration of water, the rain water will enter the wall through crack & will travel down.       

☛Rain beating against the external wall.
 If the heavy rainfall strikes the wall & the wall is not treated properly.  
☛Condensation.
Due to atmospheric moisture, water is deposited on wall, floor & ceiling which may cause dampness.  
☛Poor drainage of a building.
 If the drainage work in a building is not layout properly.
☛Improper slope of roof.
  If the slope of roof is not constructed properly.



What are the various effects of dampness?

  • It give rise to breeding of mosquito & create unhealthy environment
  • Transportation of water through walls causes patches on the wall. 
  • The decoration of the walls are damage. 
  • Presence of moisture causes efflorescence in wall which disintegrate tiles, bricks, stones etc.
  • Wood furniture and components of doors & windows are damaged 
  • Moisture presence causes rust in  reinforcement steel bars, which reduce the strength of the structure.

What are the various methods of preventing dampness?

  • Damp proof course(dpc): membrane damp proofing 
  • Integral damp proofing 
  • Cavity wall construction 
  • Guniting 
  • Pressure grouting

Damp proof course(dpc): membrane damp proofing 

• It includes some flexible membrane like bitumen, mastic asphalt, polythene sheets, metal sheets, cement concrete etc. 

• applied either horizontally or vertically on floors & walls.

Integral damp proofing 

 Chalk & talc may fill up the concrete voids under mechanical action principle. 

 Alkaline silicates, aluminum sulphates, calcium chlorides react with concrete to form waterproofing compound. 

 Compound like soap, petroleum, oil & fatty acids like sodium ammonia work on water repulsion principle

Cavity wall construction 

  • Effective method of preventing dampness.     
  • primary wall of building is shielded with outer skin leaving a cavity or little gap between the two.

Guniting 

Impervious layer of rich cement mortar is deposited under pressure over the exposed surface for waterproofing over pipe, cistern etc for resistance to water pressure.

Cement mortar of 1:3 is used. Procedure:- 

By using cement gun, mortar is applied on the surface under pressure of 2-3 kg/cm².

 Nozzal is kept at 75-90cm away from surface. 

Curing shall be done for atleast 10 days to achieve the desired strength.


Pressure grouting 

  • In this method, cement grout is forced into the cracks, voids & fissure in the structure. 
  • pressure grouting can be used for crack of various size and length & for various depth.

      


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