Any structure, such as a house, has to deal with the forces of mother nature: wind, sun, rain, and snow. Their combination affects the integrity of the structure.
As such, the structure is constructed with an exposed terrace or top level. This is where it endures the maximum direct impact of the sun and rain. The external facade of the building i.e. the principal front of a building that faces on to a street or open space also sustains varying degrees of wind, sun, and rain.
Due to the behavioural difference of action of these weather phenomena on the ground floor and at terrace level, some kind of i.e. movement always takes place in the overall structure. Generally, they are within acceptable limits for most of the structure as designed. However, it is a common observation that weather damage is more toward the top of the structure as compared to the bottom.
Now, the construction of any structure requires the use of a wide variety of materials. Each one has different properties. Depending on its basic build-quality and the manner in which it is constructed and maintained, the variation of properties leads to separation cracking between different surfaces of the building. Such cracking is a common occurrence in present-day construction.
There are three stages where action needs to be taken:
Pre-Construction Stage
Meticulous planning and designing by the architect and structural engineer with detailed working drawings, specifications, and estimates for inviting tenders is a must. Engineers/design consultants prepare various service systems including designing building facades in such a way so as to repel water and facilitate easy flow.
Technical investigation of underground soil, site survey/levels, and past data of stagnation of water on low lying area need to be done prior to commencing design.
Construction Stage
Proper management, supervision, monitoring, and total quality control is required during construction. All this can be done by prudently selecting a reputed contractor who ensures the application of project management and best quality control practices. Additionally, the waterproofing contractor also ensures that everything goes as per approved architectural drawings, engineering details, and specifications.
Post-Construction Stage
After the construction is complete, it is time to rectify defective works. Besides, efficient maintenance works including special repairs should never be ignored.
Construction of a building is a joint effort by numerous people. Waterproofing is the ultimate test of their work done by all of them. Any mistake in the design or faults made during the construction process will come to light in the form of leakage.
Waterproofing work should be done with the utmost attention to every single detail. Vigilance is key.
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Reasons for Roof Waterproofing Failure
Without further ado, let’s discuss the most common reasons for waterproofing disasters.
01. Incorrect Diagnosis of the Leakage Problem
The source of leakage is not always located near the visual marks of it. After entering the body mass, water flows in all possible directions. The source might not be where you see dampness. It might originate from somewhere else. Thus, careful and studied manual inspection is required to identify the true source of leakage.
A study of construction sequence and activities will help in arriving at the conclusion. The information provided by the people making use of the premises may also help in detecting the root cause.
Electronic probing instruments often prove useful in the detection of an underlying water source.
On the collection of data from different sources, a conclusion should be drawn and accordingly the material and the method to be used for the treatment should be decided. Any mistake in judgment here may result in the failure of waterproofing.
02. Faulty External Plastering
During waterproofing of punctures after repairs or modifications of walls, plaster or any part of a building, the envelope is left carelessly without cover treatment on it. For example, during external plastering, the holes provided in the walls for scaffolding are never filled properly nor corrected after filling.
Moreover, waterproofing treatment cannot be carried out in patches. It has to be all over on the exposed surface of the structure. Dependence on local or partial treatment should be avoided.
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03. Improper Selection of Waterproofing Material
Wrong selection of material will certainly result in the failure of the treatment. In the market, many waterproofing chemicals are available. However, each one has a specific use case.
When these waterproofing chemicals are used in the wrong way at a wrong place, the treatment is bound to fail, sooner or later.
In larger structures, when expansion joints are provided with the waterproofing material to cover the gap, they should be flexible enough to stretch along with the bodies. It should also come back to its original state when required. If the material does not keep pace with the movement of the structure, then it will fail eventually. So, the filler material has to be flexible. Application of rigid compounds won’t work here.A point where two or three different types of building materials form a joint is termed as a composite joint. At such places, the waterproofing material used has to be compatible with all the surrounding materials or else the treatment will fail. For example, waterproofing of aluminium or wooden window frame fitted in the wall.
Epoxy is formulated in part A and B. The proportion differs with every manufacturer. When they are mixed in the right quantity, they form a third product which is completely different from the first two. Same way, certain products in polyurethane require the catalyst to initiate the chemical reaction. Till then, the product is not effective. And if the manufacturer’s instructions are not followed thoroughly then the product will not perform and will malfunction, resulting in failure of the system and hence purpose.
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04. Not Carrying Out Proper Preparatory Work
Before commencing waterproofing treatment, it is essential to do preliminary work, such as:
- Cleaning the surface to remove dust
- Filling all the holes, cracks and cavities
- Repairing the damaged sections
- Relocating the embedded pipes
- Removing the residual waterproofing material from the earlier treatment
- Applying recommended primer
- Core cutting in concrete made for the pipe fitting needs to be properly finished.
Any lapses in systematic preparatory work will lead to the failure of the system.
05. Use of Incompatible Materials
Various integrated systems and products are used together to achieve the required waterproofing effect. The products used may be solvent based, oil based, or water soluble. These products do not always complement with other materials when used in combination. Certain products might have to be used early or at a later stage. They will not form one monolithic treatment.
Tar with its characteristics does not have good bonding with certain polymeric or rubberized products. If such products are used in combination, the system inevitably fails.
06. Design Flaws
When large-sized unprotected openings are constructed in the direction of the rain, then water can easily enter the building. The designer has to consider the junctions carefully and take into account the terminations that coming across.
The provision of flashings, mouldings, drops and slopes needs scrupulous planning. Staircase landings should be well protected from spilling of rainwater through the ventilation openings.
The members of the R.C.C grid designed with joints and junctions need to be properly covered. Such places are critical for water to get into the body mass. The designer should visualise these areas and provide remedial solutions to such impending problems.
Old palaces and monumental buildings are often decorated with intricate designs. The ornamental design is not just for aesthetic purposes, but also to channelize free-flowing water into the direction of the terminal drainage system. This proves that waterproofing can be achieved by cleverly devised design systems too.
07. Lapse in Supervision by Architects, Engineers, Contractors, and Owners
Any mistakes in the detailing of the drawings or during the execution of the job will lead to the failure of the system. Careful supervision of the work being done should be top priority.
When large size coating material is applied on extremely porous surfaces, it does not penetrate. The surface gets heated due to continuous exposure to the sun. The air trapped in the cavities causes the hairline cracks to expand and form blisters on the surface which, in turn, delaminates the film.
08. Blunder in Detailing of Junctions and Terminations
An uniform treatment cannot be used at all spots on the surface. Treatment at the junction and the transition of the plane needs to be different than the one given on the plain surface.
The drops, openings, and flat surfaces should be properly safeguarded by providing flashing, moulding, slopes, and so on. Areas with large span typically require treatment with a breaking of continuity and tolerance for movement, failure of which will crack the surface. A mistake in locating critical areas will again result in the failure of the system.
09. Not Adhering to the Manufacturer’s Instructions
Last but not least, it is important to follow to the manufacturer’s guidelines. Most of the modern waterproofing materials have polymer as a base. These chemicals are designed to perform different tasks for which they are specially made, and therefore the manner of their application becomes pivotal.
Many waterproofing chemicals have a pot life or shell life i.e. they need to be used within a certain time after opening the container. They lose their efficacy after expiry. Likewise, if they are not mixed properly, they may not work as desired.
When all is said and done, there is not much scope for correction. Simply put, rectification is a waste of money, time, material, and labour. Therefore, it is imperative that all the supervisory level personnel are attentive in carrying out their duties carefully, during every stage of the work.
10. Final Words on Roof Waterproofing
Discussed in this post are some of the most common reasons for the failure of waterproofing systems. But the list is not exhaustive.
Concerted efforts are required in overcoming such failures. A lot more can be accomplished when everyone is devoted to the project as a team rather than mere individuals.