External Waterproofing can be classified into 3 major groups-
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- Weatherproofing of external walls,
- External Crack Rectification and,
- Expansion Joint Treatment.
It is very critical to take care of the exterior for any building as these forms the primary barrier to stop/ block water from its entry into any structure.
Due to degrading construction quality, cracks and joints are a big concern. It needs to be treated with great care otherwise even a good waterproofing system can fail. By thumb rule, for any crack/gap the Width: Depth ratio is 2:1 and general coverage is
600 ml/120 RM/ mm (RM-Running meter)
1. Weatherproofing of External Walls–The external walls face the direct brunt of rain and other changes in weather. Therefore, it is not enough to just decorate the building but also waterproof it.
2. External Cracks- can be rectified by using sealants in case of cracks larger than 1mm by opening the crack all along its length to a certain degree of width and depth followed by filling the created groove using an elastic sealant such as an acrylic paste, PU sealant etc. depending on the crack size followed by protecting the system using a waterproof coating or in case of minor cracks up to 1mm, a non-shrink grout can be used. Grout is basically a filler material used to seal a gap.
These sealants are available under the brand name of several companies e.g., Asian Paints, Dr. Fixit, Alchimica, FOSROC etc.
3. Expansion joints– Due to the low tensile strength of PCC and reinforced concrete, some cracking is unavoidable. Hence expansion joints in RCC and control joints in PCC are introduced. These joints allow thermally induced movements to occur with a minimum build-up of stress. In order to provide a cushioning effect that can absorb the stress, a rubbery waterproof material is used as filler in the joints.
In case the joint is deep, a backer rod can be placed followed by application of PU Sealant followed by coating the system with appropriate material. Also, in case of expansion joints, aluminum plates can be added for protection where there is heavy movement.