Excessive moisture or water content in the building structure is called damp. There are many causes of damp in buildings, we will discuss thoroughly the causes of dampness in buildings, types of damp, and how to prevent dampness in buildings.
Causes of Dampness in buildings:
- The use of inappropriate building material is one of the major causes of dampness in the buildings. If the material used in the construction of buildings has a patchy surface or the finishing of structural components is gritty, then it will absorb moisture.
- Moisture finds easy access through chapped surfaces or from the ground and is aided by capillary action to let the moisture travel in different directions through voids.
- If the design of the building is faulty, or the structure is built with bad workmanship, moisture may find easy access to cause dampness in the building.
- If the building drainage is not functioning properly, rainwater may penetrate from the top of the building. this will cause dampness in the building.
- Condensation is another major cause of dampness, during this process, moist air cools below its usual dew point.
Effects of Dampness in Building;
Building life cycle and looks greatly affected by dampness in the building, it reduces the life cycle of building and finishes used. There are some other effects of damp in building listed below:
- Damp in building promotes the growth of termites which is very harmful to wooden elements installed, such as wooden doors, kitchen shelves, etc.
- Dampness in the building creates an unhealthy atmosphere for the residents and promotes the breeding of mosquitoes.
- Due to the dampness, corrosion of metals in the building may take place.
- Formation of ugly patches on walls and ceilings.
- Softening and collapsing of plaster.
- Efflorescence may be caused by the disintegration of tiles, marbles, and paint.
- Damp may cause bleaching of paint to result in discolored patches of painted surfaces.
Damp Prevention Methods:
There are few damp prevention methods used in the construction industry effectively, by applying these techniques we can overcome dampness in buildings.
- DPC ( damp proof Course)
- Waterproofing Treatments
- Integral Damp Proofing Method
- Construction of Cavity Walls
- Shotcrete or Guniting
- Waterproof Grouting
1.Damp Proof Course ( DPC) Layer
The damp proof course is ideally provided +15 cm above the plinth level in horizontal and vertical directions. DPC layer consists of water-resistant materials such as Bitumen Membrane felts, mastic asphalt, cement concrete, plastics, etc. this layer is provided above the plinth level in either whole building or wherever water incursion is suspected. DPC layer restricts moisture movement and prevents dampness in building.
In normal conditions M15 concrete (1:2:4 ratio) is used in the thickness of 40mm to 50 mm. However, if the conditions are humid and wet, then a more dense concrete layer must be used aided by waterproofing materials such as waterlock or pudlo and finished with a hot bitumen layer.
Waterproofing treatments are an in-depth treatment for structures below ground such as basements and foundations, and also used for above-ground damp proofing. There are various materials used for waterproofing listed below:
- Cold Bitumen / Bitumen Sheet installation
- Damp Proof Paint
- Cementitious Waterproofing
Cold Bitumen / bitumen sheet installation
In this treatment, any vertical or horizontal surfaces are cleaned from all kinds of obstructions such as nails, and any cavity filled properly. Then two coats of cold bitumen are applied either with the help of a paint roller or most commonly with a spray machine and let dry. Once the surface is dry, then the bitumen sheet is available in various thicknesses fixed after heating the sheet and fixing.
Damp Proof Paint
Damp-proof paint is specially formulated paint to prevent dampness in buildings. It is usually applied in three coats on structural elements. It can be used on internal and external walls as a primer, we must remember that damp proof paint is not a solution to an underlying existing problem rather it can be used on newly constructed structural elements to prevent incoming moisture.
To apply damp proof paint, the area must be free from fungus, mold, or any other existed paint. It can be applied with a brush, roller, or spray machine. Damp-proof paint usually takes an hour to dry. It is available in black and white shades depends on the country of origin.
Cementitious waterproofing is another suitable type of waterproofing treatment for structures buried below ground level. Cementitious waterproofing is a unique type of breathable positive or negative side waterproofing. It prevents mold and mildew, keeps moisture out, and stops water infiltration.
There are many benefits of using cementitious waterproofing, as it is very easy to mix and apply as compared to other waterproofing solutions. It became more durable if admixtures such as acrylic are mixed with cementitious waterproofing. It is also suitable for bathroom waterproofing.
3.Integral Damp Proofing Method.
The integral damp proofing method is based on adding certain compounds to mortar or concrete during the mixing process. When used and cured completely, it acts as a complete moisture barrier and prevents moisture penetration and dampness in the building.
Compounds such as chalks, or fallers fill the pores in plaster or concrete by mechanical action principle process. This makes the mortar or concrete denser and waterproof.
Some chemical compounds such as sulfates and calcium chloride make the mortar waterproof by chemical action process. Once mixed, they react chemically to fill the pores and provides a moisture barrier.
There are some admixtures also used as waterproofing compounds such as oil, petroleum, and fatty acids, and sodium ammonium provides a waterproof barrier by repulsion action principle. Once mixed in mortar they act as water repellent.
4.Construction of Cavity Wall
Cavity walls consist of two parallel walls with no immediate contact and a gap in between the two wall sections. The gap is called a cavity. The construction of a cavity wall effectively prevents the dampness in the building and damp transmit to the internal walls.
There are some benefits of cavity walls listed below:
- Cavity wall provides good insulation against heat and sound.
- The cavity wall prevents dampness and moisture.
- Cavity wall reduces the risks of efflorescence.
- Cavity wall provides better hygienic conditions and environment.
5.Shotcrete or Guniting
Shotcreting or guniting is a method of application of dense cement mortar (1:3) overexposed concrete surface to prevent moisture and dampness in the building and others structures. The Shotcreting method is suitable for water supply and drawing pipes and cisterns to prevent leakage. By this method, a high impervious layer obtains with compressive strength of 700-800 kg/cm2. This method is also suitable for repairing old concrete works.
This method is suitable if there are cracks developed in vertical or horizontal elements of the building. In this method, waterproofing grout is injected into the cracks to seal the cracks and prevent any moisture and water leakage through them. This technique is suitable to form a barrier to prevent water leakage and repair cracks in the structure.