Waterproofing activity perhaps is practiced ever since the man moved out of caves and started living in buildings built by him. Several water proofing methods have been evolved over the years depending on the materials used in the construction, weather condition and architectural designs.
India is a unique country in the sense that it sees four different weather conditions during the year – extremes of hot and cold climate and heavy rainfall during Monsoon. A building surface has to cope with all these weather extremes which requires construction quality of highest order. However, in many cases seepages and leakages are common scenes in Indian buildings.
Also, India is a vast country with different parts of the country experiencing different weather conditions at the same time. Also, construction practices and materials used vary from region to region within the country. Traditionally various types of waterproofing methods have evolved to suit the different weather conditions, building materials, affordability and durability.
Some of the traditional waterproofing methods are as follows
Mud Phuska is a common type of waterproofing method used in hot and arid regions such as in the states of Punjab, Uttar Pradesh and other regions where the rainfall is not heavy. It also acts as thermal insulation for maintaining relatively comfortable temperature in the interior.
In this method, the surface is first cleared of dust and loose material. Then, a layer of hot bitumen is spread over the surface. Immediately thereafter, a layer of coarse sand is spread over the hot coat of bitumen. Then Mud Phuska is prepared for which selection of soil is of utmost importance. Usually soil used in brick making is used for Mud Phuska, which will be cleared of all foreign matter like stones, grass roots, etc. Water is added in sufficient quantity to make it damp and applied on the surface above the sand-bitumen layer. It is then plastered with a coat of mud-cow-dung mortar. Tile bricks are laid flat on plastered surface with joints grouted.
It is inexpensive compared to some of the other methods of waterproofing and provides relatively durable solution. However, it requires labour with special skill sets having knowledge and experience of laying Mud Phuska, which is hard to find now-a-days.
Brick Bat Coba
Brick Bat Coba is another conventional method of waterproofing that gives slope to terrace to drain away the water accumulated on terrace.
Before applying Brick Bat Coba, the terrace surface need to be cleansed off all foreign materials including waterproofing materials previously used, if any. This is usually done by cleaning the surface with hard wired brush. Also, measures need to be taken to fill all structural cracks as per standard practice.
After getting rid of the cracks, a layer of brick bats, soaked overnight in water, is laid. The gaps between the brick bats are filled with cement sand mortar, admixed with waterproofer. Immediately after this, the surface should be covered with wet gunny bags and curing should be continued for minimum seven days. Finally, the cured surface is finished with cement sand mortar, admixed with waterproofer.
This method is usually adopted for waterproofing of terrace, roofs and basements. However, this method has some drawbacks. This method puts unnecessary load on the roof. Also, finding a skilled labour to do this type of waterproofing is difficult. Quality of work done by inexperienced labour will always be suspect.
Lime Surki Method
This method has been in use since time immemorial. This treatment is, however, most successful where temperature variation is less since the lime concrete itself cracks under wide temperature variations.
Various proportion of brick aggregate, Lime Surki and sand mixed to make a lime concrete of thickness 75 to 100 mm, which is rammed and subsequently beaten with wooden thappies for three to four days as it slowly sets. While beating the surface, it is liberally sprinkled with a mixture of gur and boiled bael fruit in water.
This method was popular with the Indian Railways in the past.
Hessian based tar felt is the most common product for water proofing on the new Roofs. These felts use hessian as the barrier medium for bitumen and bituminous Compound. There are different grades of bitumen felt and these grades refer to minimum weight of bitumen felt.
However, short life of the bitumen felt is its main disadvantage as the contents of a factory finished felts are not viscous enough to retain the shape and intended characteristics of roofing felt. also, Hessian being organic in nature is subject to decay within a short time, resulting in decrease in tensile strength and life of tar felt. Further, defective lap joints often allow seepage of water.
Box Type Water Proofing
To start with the surface need to be cleaned with wire brush and all foreign matter should be removed. If there are any cracks on the surface, the same should be filled with cement mortar. Fix the rough Shahabad tiles on reasonably thick cement mortar rendering. Tiles are placed in staggered pattern by keeping 20 mm joint in between the tiles. Then gaps are filled with medium size aggregates mixed with cement mortar with admixtures. Finally, the surface need to be cured for 15 days before being ready for use.