Many people have reservations about vegetative roofing with one of the main fears that they can easily leak. However, a properly designed green roof system will not necessarily leak. For example, a waterproofing layer is usually installed between the planting medium and the rest of the roof structures to prevent leakage. There are also tests you can use to confirm whether your vegetative roof will leak. Here are two examples of such tests:
In this test, a continuous flow of water is sprayed on the roof's surface for a short while. The spraying is designed to mimic natural precipitation, such as rainfall. The test results indicate your roof's risk of failing under heavy rain. It is suitable both for flat roofs and pitched roofs. For it to work best, the test must be started on the lower parts of the roof. If you start by spraying the upper parts of the roof, then the water may flow down the roof and mask any leaks that may appear on the lower parts.
Since it is controlled spraying, you don't have to worry about having too much weight of water on your roof at a time. This means you can use it on a weak roof that cannot handle the weight of standing water. Also, it is relatively fast, and you don't have to block the drainage outlets during the test. Unfortunately, it does not help you to understand the effect of hydrostatic pressure on the roof, such as would occur after prolonged rain.
Just like the name suggests, it involves flooding the roof with water and monitoring it for possible leaks. The drains are plugged, and the roof is flooded with adequate water; this is followed by close monitoring for several hours. During the testing period, the underside of the roof is examined for any possible leaks. The drains are then unplugged and then the water is drained off. Care must be taken to ensure that the roof structure can bear the weight of the flood water without damage.
One of the best things about this method is that it tests the entire roof at once. However, it is time-consuming and tricky. For example, you can easily overload the roof, damage it and cause a leak – the very thing you were trying to test in the first place. These are just two examples, but there may be other tests that your roof contractor may suggest. Don't forget that they should be carried out before the vegetative matter is added to the roof so that leaking parts of the roof can be fixed conveniently.
When roofing contractors from a company like Roofs by Rodger are installing your vegetative roof, you can ask about how they will test the waterproofing layer to ensure that your roof will not leak.