Table of Contents
As per our experience, many customers have frequently asked, why is it necessary to do the waterproofing of the parapet wall. Here we have tried to explain the importance of parapet wall waterproofing.
These days we have observed that many of the waterproofing applicators & vendors have adopted shortcuts to get the project or complete the work early. Also, it has been observed that such vendors/applicators try to take advantage of the lack of technical knowledge of the customers. This is definitely not the long-term waterproofing solution as they are focusing on terrace waterproofing while neglecting an important area of the terrace i.e., the parapet wall.
As we are already aware that concrete is formed through the combination of different materials like cement, fine aggregate (sand), coarse aggregate (stone), and water. One of the vulnerable properties of concrete in terms of waterproofing is that concrete has a lot of air gaps between its molecules which makes concrete porous in nature, hence easily exposed to water seepage.
The image above is a microscopic image of the concrete, showing air gaps within the molecules of concrete. These air gaps are prone to water ingress.
The next section, explains parapet wall waterproofing in detail.
Parapet Wall Waterproofing
The parapet wall is also made of concrete and with due course of time, there are always a few cracks formed on it. During rain, the water enters the parapet wall through these cracks or by directly getting absorbed by the concrete surface. This seeped-in water then travels down in a vertical direction due to gravity and inside the horizontal slab surface resulting in seepage.
We have formulated three different cases for easy understanding of the concept:
Surface without waterproofing – With due course of time, the terrace and the parapet wall both develop cracks because of which the water seeps inside the building resulting in seepage/dampness.
In the above image, it can be seen that cracks have formed on both the parapet wall as well as the terrace/roof horizontal slab resulting in seepage of water
The water has entered into the terrace slab through the cracks formed in the parapet wall and on the horizontal surface resulting in the seepage.
- Waterproofing on horizontal surfaces only – This method is generally adopted by local waterproofing vendors in order to reduce their quotation, claiming that the work has been done by them at a lower cost. If the waterproofing is done only on the terrace slab and not on the parapet wall, it still results in the failure of the waterproofing.
In the above figure, the waterproofing has been done only on the horizontal surface of the terrace.
In the above figure, it can be seen that though the crack on the horizontal surface has been filed as well as the waterproofing is done on the terrace slab, the waterproofing still fails. The reason of the waterproofing failure is:
- The cracks on the parapet wall are left unattended
- The water is absorbed by the parapet wall as there is no waterproofing layer to obstruct it.
It means, that even if the crack filling is done on the parapet wall, seepage will still take place, as the water will be getting absorbed by the parapet wall due to the unavailability of any barrier.
- Proposed Solution: This case includes a solution for terrace/roof waterproofing wherein waterproofing of the parapet wall is done from both directions – internal and external faces, along with the terrace slab, to ensure that the terrace is waterproofed from all sides.
In the above figure, the waterproofing is done on the horizontal terrace surface as well as on the parapet wall’s internal and external faces.
In the above figure, the crack filling, as well as the waterproofing, has been done on the parapet wall and the horizontal surface as a result no seepage has been observed. This has happened due to a strong waterproofing barrier across the terrace.
As per our experience, the proposed solution is long-term and most durable. The initial cost of installing waterproofing on the parapet and horizontal surface will be slightly higher. It has been observed that the solution results in a maintenance-free terrace or roof for a much longer period of time when compared with waterproofing done only on the terrace or horizontal surfaces which requires frequent maintenance.