What Is Waterproofing?
Waterproofing is a process of protecting civil structures from water. The ingress of water causes the leakage of water into the structure that deteriorates the aesthetics of the structure. The structural integrity is also threatened.
The structural elements coming into direct contact with the water are prone to water leakage. The exposure to water may be due to the rains, high water table, faulty conduits, stagnant water, etc. The roofs, kitchens, bathrooms, external walls, balconies, basements, and swimming pools are such structural elements that often require waterproofing.
Waterproofing shouldn’t be confused with damp-proofing as both the process deals with the prevention of water. The waterproofing is done where the volume of water is substantially higher whereas the damp-proofing is the prevention method for dampness or humidity.
Advantages Of Waterproofing
The various advantages of waterproofing are listed below:
- The structural integrity is protected.
- The steel rebars are protected from corrosion.
- The wooden furniture and building elements like doors, windows get longer life.
- The paint on walls/roof remains intact hence aesthetics are maintained.
- Waterproofing checks the insect infestation.
- The atmosphere inside the structure remains dry hence electronic equipment like TV, AC, computers etc. are safer from damage due to moisture.
- The plaster doesn’t swell or comes out due to water leakage.
- The property value increases due to the leak-free structure.
- The hygienic living conditions are promoted.
Types And Methods Of Waterproofing
The waterproofing can be done either at the time of construction or afterward. Both types of waterproofing have their pros and cons. Let us discuss these waterproofing types in detail.
1. Integral Waterproofing
The waterproofing done at the time of construction is called integral waterproofing. This type of waterproofing is always beneficial as it has low cost when compared to the lifetime cost of the structure. Moreover, the integral method allows the owner to live stress-free of the leakage problem.
The silica fumes or silicates are used to fill the pores to clog the water passage.
The hydrophobic polymers cover the pores and stop the water flow.
The chemical produces non-soluble crystals when it comes in contact with the water. The crystals plug the pore.
The compatibility of integral waterproofing chemicals with the concrete is checked beforehand. The percentage use of chemicals is also determined as per the requirement.
Advantages Of Integral Waterproofing
- It is a faster method.
- Cheaper as compared to non-integral waterproofing.
- More reliable.
- No skills are required to implement.
- No installation is required.
- It does not get damaged due to external works like backfilling etc.
- The integral waterproofing does not wear out.
- More convenient for deep foundations, tunnels etc.
2. Non-Integral Waterproofing
The waterproofing methods that are implemented after construction are non-integral methods. These methods are generally corrective and resolve the existing leakage problems. The non-integral waterproofing methods are of below-mentioned types.
3. Liquid-Based Waterproofing
Specialized waterproofing liquid chemicals are available on the market. These chemicals are directly applied over the surface to be treated. The liquid-based waterproofing chemicals turn elastic on drying. It has the property of stretching and coming back to its’ original position. Hence, it doesn’t develop cracks due to the expansion or swelling of concrete.
The three coats of liquid are applied as one coat primer and two top coats. The coats can be applied by roller, trowel, or spray. The coats can be applied over asphalt, bitumen, or concrete and offer a sufficiently good life of up to 20-25 years.
4. Cementitious Waterproofing
Cementitious waterproofing is an easy technique to apply. It is a cheap and helpful method for places that are always wet or underwater. As the cement doesn’t have elastic property, it cannot elongate or expand.
Hence, the dry conditions may crack the concrete and beat the overall purpose of waterproofing. Suitable chemical additives are added to the cement which improves the waterproofing performance and durability.
5. Bituminous Coating Waterproofing
Bituminous is a by-product of the petroleum industry. It softens on heating and hardens on cooling. It is the cheapest method of waterproofing. The bitumen is sprayed over the surface to provide a thin film that prevents the ingress of water.
Bitumen coating is not suitable for direct exposure to sunlight without modification with polymers. Hence, it is commonly used on foundations. It is also a good option to be used below screed. Also, it is a very reliable method for basement waterproofing. However, this practice has been mostly discontinued.
6. Bitumen Sheet Waterproofing
Bitumen sheets are prepared by jute fabric or fibreglass mats with chemically modified bitumen. The bitumen sheets are laid on the roof over a bitumen primer. The two layers are joined together by a heating torch.
The bitumen sheet is not a suitable option for the concrete roofs as they are airtight as well. Hence, the breathing property of concrete is obstructed causing blisters that affect the quality of concrete. However, they are a perfect solution for asbestos cement sheets and zinc sheets.
7. Polyurethane Waterproofing
The polyurethane waterproofing method uses two chemicals- a base and a reactor. The base is a polyol and the reactor is isocyanide. The two chemicals form a liquid coating over the surface. The application method requires acid-washing of concrete and torching it to make the surface completely dry.
The multiple stage implementation method makes it an expensive method. Also, the method has failed as it develops cracks upon direct exposure to sunlight. The stripping of the polyurethane is a common problem if the concrete has not been dried properly. Due to the disadvantages, the method has been discontinued.
Conventional Methods Of Waterproofing
Other than the above-mentioned methods, several more methods have found their extensive use in the past. These methods have been discontinued due to availability of the better and economical materials and techniques.
1. Brick Bat Coba Method
The burnt brick bats were mixed with lime mortar and laid on the roof. A gentle slope at the top was maintained to drain off the rainwater. The method was popular in India under British rule. The method was cheap and effective.
The brick bat method also kept the house interior cool. It lasted for up to 15 years if done by skilled manpower. However, it had a serious drawback. During heavy rainfall, the brick bats absorbed too much water that made the water leak. The roof also got heavy.
2. Metallic Sheet Wrapping
The thin foils of copper and aluminium were wrapped around the leaking concrete surface. The method failed due to the unavailability of a common jointing material for the thin sheets and concrete.
3. Epoxy Based Waterproofing
This method used a base resin and a reactor just like the polyurethane method. The method failed for the reason that epoxy couldn’t withstand the alkaline nature of the concrete and hence needed to be acid-washed. Also, the thermal expansion of concrete and the epoxy is different hence the method couldn’t be used on the exposed surfaces like roofs.
4. Box Type Waterproofing
The box type waterproofing method is used for underground structures. The structure is covered from all directions.
The impervious stone slabs were put into excavated pits over blinding concrete. The joints between the stone slabs were filled with rich mortar mixed with an integral waterproofing chemical. The stone base continues to the wall up to ground level and covered the entire structure.
Points To Consider For Waterproofing
There are few things that need to keep in mind when implementing a waterproofing method for homes, buildings, roofs etc. Some of them are mentioned below.
- The drains should be cleaned before monsoon so the water flow is not obstructed.
- The source of water leakage must be identified and rectified immediately be it a construction joint, leaking conduit, crack in concrete etc.
- The integral water techniques are modern, cheap, reliable and most convenient and hence during construction they should be implemented. The cost of waterproofing is about 1 % of the building cost.
- The joints in the structure should be carefully planned and treated as soon as they are made.
- Before choosing a waterproofing system, always consult with an expert for material, technique and contractor selection.
- Ensure that the packing of waterproofing materials is not tempered. The material exposed to the atmosphere may lose its waterproofing properties.
- Supervise the job and ensure the materials are used as per the specifications of their respective manufacturers.
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