Rainwater Leakage in Buildings : 7 Causes & Prevention

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Before starting the process of waterproofing building components, its cause should be determined.

The problems of rainwater leakage in buildings can be classified as follows:-


  A. Rainwater Leakage in Buildings  



1. Leakage in the flat roof  terrace   



The stagnation of water on a flat roof is one of the common reasons for leakage and dampness in the building. Leakage happens on a flat roof due to bad drainage also.



The slope of the roof terrace should be constructed so that the rainwater drains off before seeping into the roof.

The minimum recommended slope for a roof covered with tiles is 1 in 60.

For non-tiled rough surfaces, it is 1 in 40.


Leakage in the flat roof  terrace   



2. Leakage in shells and sloped roof



~ Lack of compaction during the construction phase due to difficulty in compaction by vibrator.

~ Use of porous concrete.



~ Always use dense concrete.

~ All the valleys should be checked for leakage and grouted at the construction stage.

Waterproofing coating in the form of a bituminous coat can also be applied. Check for the provision of the gutter, cave gutter, valley gutter, and boundary wall gutter.


Rainwater Leakage in Buildings



3. Leakage through the Junction of the wall and sunshades



Stagnation of water at the junction between the wall and sunshade.

Continuous long sunshades without joints or gaps tend to crack at interval.



Give proper slope for quick drainage of the sunshades at the construction stage. Provide a fillet or goal by plaster at the wall junction.

In the case of a sunshade crack, fill these cracks with an elastomeric compound that can accommodate the movement of joints.

All leaves collected over the sunshade should be cleaned, especially during the rainy season.




4. Leakage through cracks on External Walls



Improper curing & Improper mix of materials are the leading causes of cracks in external walls.



All the cracks formed on the external wall should be deepened to 5 mm and filled with proper sealant.


Leakage through cracks on External Walls



  5. Leakage at Junctions of outer walls with roof slab and other floor slabs  



Due to the difference in the expansion of concrete and masonry, If there is a small gap at the junction of the external face, the water that flows down the exterior wall tends to be sucked into the building.



Provide a drip course with a projection with a shaped groove, called drip, by extending the slab beyond the wall or by constructing a separate drip course in a framed building in the form of a bend at the junction.

In the case of the existing building, the joint has to be sealed with a waterproof sealant or by applying elastomeric paint with glass fiber.





  6. Leakage from external electric points  

All the external electrical points and fittings should be sealed with suitable sealants and waterproof.

Any wires and pipes taken into the building should be bent down. It should not carry water inside the building.



7. Leakage from expansion Joints of slabs or beams

Expansion or other joints provided by the designer in slab and beams should be appropriately filled with approved joint fillers.

Joint fillers are special material that allows movement of the joints.




Read Also: DPC(Damp Proof Course)



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