What is Waterproofing?
Waterproofing in building construction is the process of making a structure water-resistant or impervious to the ingress of water. Waterproofing is essential as it prevents water from penetrating buildings and helps to keep the interior areas dry. It helps in reducing the humidity inside the building, minimizing the damage done to furniture and alike.
In areas that experience high annual rainfall and occasional flooding events, water proofing is a must. It is important for basements and foundations to be waterproof especially in areas where the ground water table is high. In the case of high water table, water in the soil is likely to exert hydrostatic pressure on the basement floor and walls. This can force the water through the cracks, which can result in structural damages along with moisture-related problems such as mold, mildew and decay.
During monsoons, we all would have come across water seepages in the ceilings and walls or dampness in the aftermath of flooding. This is due to poor waterproofing. By waterproofing your house, you can safeguard your building from damage as well as the things inside your house from humidity and water exposure.
Advantages of waterproofing
- Safeguards the structural integrity of the building
- Prevents mold, mildew and decay
- Prevents metals from rusting and wooden furniture from decay
- Prevents seepages from the ceiling and walls
- Prevents dampness inside the building
- Property value increases
Unhealthy living areas and a weak foundation can significantly reduce the property value. Waterproofing increases the resale value of a building, which is perhaps one of the biggest advantages. Investors/buyers hardly even consider houses without waterproofing. Several homeowners live in houses with damp and leaky basements, often fearing the cost of waterproofing. However, getting this essential exercise done with fetches noteworthy rate of return. A waterproofed basement increases the utilizable square footage in a house, simultaneously ruling out the possibility of a looming structural failure.
Waterproofing Methods & Techniques
Brick Bat Coba Method
RCC slabs sometimes develop cracks, which allows for a passage of rainwater. It is therefore important to develop water-proof roof slabs, which can provide leak-proof environment to the interiors of the building. This method requires a roof surface slope for quick drainage and sealing of all cracks and joints. Flat type roof with RRC is used in climates with moderate to low rainfall. Coba treatment can be carried out directly on RCC or stone slabs.
- The surface of the roof slab should be cleaned and washed with water before laying the first course
- A fresh slurry is prepared by mixing cement with 1-2% super seal powder (acrylic based acrylintryl chemical)
- The slurry is first mixed dry and then water is added until it reaches a uniform consistency
- This freshly prepared slurry is spread on the cleaned roof surface to create a smooth thin layer
- Cement sand mortar is prepared by adding 1-2% super seal powder in a 1:5 cement sand dry mix (1 part cement, 5 part sand)
- Water is added to obtain a plastic mortar
- This cement mortar is spread on top of the thin slurry layer to obtain a 20mm thick cement mortar layer
- Brick bats are inserted in the 20mm cement mortar layer to create a 100-150 mm brick bat later layer
- The cement sand mortar is then used for grouting the previously laid brick bat layer. All voids and joints are filled. Ensure a smooth slope surface over the brick bat layer
- Freshly prepared plastic cement sand mortar is further spread on the grouted brick bat layer
- The grouted surface is allowed to cure for 2-3 days to avoid surface cracks.
- Another cement sand mortar is prepared (1 part cement, 5 part sand) with 1-2% super seal powder. Water is added until the mixture is consistent.
- 20mm thick layer of this mortar is spread over the brick bat mortar layer
- A trowel is used for finishing. Square markings can be made by string or trowel. This is to prevent surface cracking due to expansion or contraction in response to temperature change.
- Curing is continued for 2 weeks
A water-proof membrane is a thin layer of water tight material that is laid over the surface. Stagnated water is likely to seep into the structural slab overtime. In flat roofed terrace, the membrane is laid over a filler material that is sloped to ensure that water is drained away by drainage pipes.
Sheet Based Membranes
Sheet based membranes come in the form of rolls. These are unrolled and laid on the firm surface. One of the most common sheet based membrane is the bituminous waterproofing membrane.
Liquid Applied Waterproofing Membranes
These are the kind of membranes that come in the form of liquid that can be sprayed or brushed onto the surface. By spraying, the liquid forms a monolithic membrane, with no laps, welds or seams.
To read more about waterproofing techniques using membranes see this article.
Polyurethane Waterproofing Treatment
Polyurethane is made up of two components, base and reactor. Polyol acts as the base, while isocyanide is the reactor component. The combination of both these in a specific design ratio creates a liquid coating for waterproofing applications. Polyurethane is a rather popular choice due to its ease of installation.
To read more about waterproofing techniques using Polyurethane treatment see this article.
Concrete joints are most liable to seepage. Waterstops are elements of a concrete structure that prevent the passage of water through concrete joints. They are designed as fluid tight diaphragm embedded in or running along the joints.
Apart from all these methods explained here, basement waterproofing demands skilled and expert procedures. You can read more on basement waterproofing here.