Waterproofing in buildings is the formation of an impervious barrier over surfaces of foundations, roofs, walls and other structural members of building to prevent water penetrations through these surfaces. The building surfaces are made water-resistant and sometimes waterproof.

Commonly used materials for waterproofing in building is cementitious material, bituminous material, liquid waterproofing membrane and polyurethane liquid membrane etc.

Waterproofing in buildings and structures are generally required for basement of structure, walls, bathrooms and kitchen, balconies, decks, terrace or roofs, green roofs, water tanks and swimming pools etc.

The following waterproofing methods are commonly used in construction:

a. Cementitious Waterproofing:

• Cementitious waterproofing is the easiest method of waterproofing in construction. The materials for cementitious waterproofing is easily available from suppliers of masonry products, and they’re easy to mix and apply.
• This method is often used in the internal wet areas such as toilets. This method is usually a rigid or semi-flexible type waterproofing, but since it is used in internal areas such as toilets, it is not exposed to sunlight and weathering. Thus cementitious waterproofing does not go through contract and expansion process.

Liquid Waterproofing Membrane

• Liquid membrane is a thin coating which consists of usually a primer coat and two coats of top coats which are applied by spray, roller, or trowel. It offers more flexibility than the cementitious types of waterproofing.
• The liquid cures into a rubbery coating on the wall. The elongation properties of the coating can reach as high as 280%. The durability of the waterproofing coating depends on what type of polymer the manufacturer use for the making of the liquid waterproofing.
• Liquid waterproofing membrane can be of spray-applied liquid membrane composed of polymer-modified asphalt. Polyurethane liquid membranes in separate grades for trowel, roller, or spray are also available from various manufacturers.

Bituminous Membrane

• Bituminous membrane waterproofing is a popular method used for low-sloped roofs due to their proven performance. Bituminous waterproofing membrane have torch on membrane and self-adhesive membrane.
• Self-adhesive compounds comprise asphalt, polymers and filler; additionally, certain resins and oils may be added to improve adhesion characteristics. The self-adhesive type has low shelf life as bonding properties of the membrane reduces with time.
• Torch on membrane have exposed and covered types. Exposed membrane often has mineral granular aggregate to withstand the wear and tear of the weathering and the other types of membrane, contractor need to apply one protective screed to prevent the puncture of the membrane.

Bituminous Coating

• Bituminous coating is a type of coating used for waterproofing and flexible protective coat in accordance with its formulation and polymerization grade. Its flexibility and protection against water can be influenced by the polymer grade as well as reinforcement of fiber.
• Bituminous coating is also called as asphalt coating. The most common applications of bituminous coatings include areas that are beneath screed wet. It is an excellent protective coating and waterproofing agent, especially on surfaces such as concrete foundations.
• Bituminous coating is made of bitumen based materials and it is not suitable for expose to sunlight. It becomes very brittle and fragile when long exposure to the sunlight unless it is modified with more flexible material such as polyurethane or acrylic based polymers.
• The flexibility of the finished products always depends on the solid content of the polymer added to the bitumen.

Polyurethane Liquid Membrane

• Polyurethane liquid membrane method of waterproofing is used for the flat roof area and exposed to weathering. This waterproofing method is expensive.
• Polyurethane Liquid Membrane can offer higher flexibility. Polyurethane is very sensitive to moisture content present, therefore before application, one has to be very careful evaluating the moisture content of the concrete slab, otherwise peeling or de-bonding of membranes may happen after some time