When executing a flat roof, one of the tests to ensure its correct execution is watertightness. Of all the elements that make up a building, it is undoubtedly the roof that can present the most pathologies. It does not matter whether the roof is flat or inclined, in both cases the pathologies are usually similar and serious. First of all, today we will clarify what a cover is, and what does not seem like it, we must be clear about what it is. One of the biggest problems that a cover can present is its lack of watertightness. Therefore, in the execution process, tests are carried out for verification.
The roof of a building
Three elements make up the construction of any building or house, the structure, the enclosure and the roof. In the structure We already include the necessary foundation. It is the skeleton of our building, the entire construction is based on it. Composed of vertical and horizontal elements, the latter form the different heights of the construction. The enclosure They are the vertical walls that close the walls of our building. In the case of our prefabricated homes, concrete is the material of this enclosure. Added to this are the exterior carpentry and the glass that completes the enclosure.
As for the the cover, we can have it of two fundamental types. Sloped roofs or flat roofs. After each of them there are more sub-types depending on the material used or the way of executing them. The flat roof, specifically its watertightness tests, is what we are going to deal with today.
Tightness tests, flat roof
It is virtually impossible to eliminate the possibility of defects in the workmanship of a deck with a visual inspection. We are referring, of course, to defects that affect its waterproofing. At first glance, there are no defects that could be the source of water leaks. To check and consider the roof waterproof, it is necessary to use tests or watertightness tests.
On flat roofs, the test is carried out by flooding the roof. For twenty-four hours it should be left flooded and under observation. What should be observed? Once the test is finished we must look for signs of leaks under the cover. The correct thing to do is to proceed with this leak test twice. A first time on the waterproofing fabric, before the drainage holes are drilled on it and before the placement of the final roof package. The second phase of the tightness test is with the cover completely finished. There are a couple of exceptions to this premise. For example in green roofs or that have floating flooring as a finish. In these cases, the second test is carried out with the drains executed but without the placement of those final elements.
How to take the test
The first thing we must do is plug the different deck water evacuation points. With this we ensure that the flooding is constant without losses. These losses could deceive us and make us see that there are leaks, when what happens is that the cover displaces the water. Then we fill the deck with a hose, how far is a good question. We call the limit to which we must fill the logical limit. This is the one that does not allow overflow above the vertical delivery of our waterproofing. It is necessary to comply, as it cannot be otherwise, with current regulations and with what is designed in the execution project with regard to the length of this vertical delivery. If we flood above it, it is easy for water to pass behind the waterproofing sheet.
A good system is to fill in units of five centimeters, and leave that safety distance before reaching the lowest point of the sheet delivery. Sometimes the design of the cover, the slopes of the panels can prevent complete flooding of all the panels. Something acceptable in this type of essay. Speaking of cloths, what cannot be assumed is the test carried out on cloths and not with the entire cover. Water can easily overcome the joints between these cloths. Another point to control is the access holes to the roof. In these accesses, the vertical level of delivery of the waterproofing must be respected in the same way. An execution error in these gaps can deceive us about the tightness of the cover.
Finishing the test
Once the twenty-four hours of the test have passed, we have to empty the cover. It has to be done progressively. This will prevent water hammer in the downspouts. It is a perfect time to check the status of the vertical roof water evacuation network. Looking for defects in the bends that form the conduit and even in the inclined sections parallel to the slab. A fact that, if normal, is almost anecdotal is that the water level is maintained throughout the test. Obviously, if this level has decreased drastically before the deadline expires, it could be a sign that something is going wrong. But minimal variations should not be attributed to the tightness of the cover. The season of the year, the temperature of the environment, the degree of humidity, are factors that vary this level. All of them unrelated to the execution of our cover.
When the cover does not have the appearance of a cover
A very common mistake is not treating what a cover is as what it is. We explain, there are horizontal sections of the construction that, although they do not crown it, are still roof elements. The roof has a very clear purpose to close the upper part of the building. That's why we all understand that a roof is the roof of the house. But so is a terrace. The terraces must be waterproofed in the same way as the upper deck. They have the clear mission of not letting water pass through, in any case of evacuating it through the systems implemented to do so. It is also a roof that covers a basement but is outside the volume of the house. On top of this horizontal panel it is easy to have urbanization areas such as gardens. They are not above our house but in the latter case, their poor execution can bring humidity to the garage or basement areas.
A very common mistake in traditional construction frequently occurs in underground parking. Waters are closed with the horizontal slab, and on top of this, a park, a sidewalk is developed, etc. Streetlights and other elements are placed that end up perforating the waterproofing sheet. This way we can enjoy those underground parking lots that look more like caves, due to the existing humidity.
