As the Green Roof industry grows, we are finding more instances where people reject the idea of a green roof on their building due to a lack of information (or misinformation). So here at Sow Green, we are setting out to combat some misconceptions about green roofs with a series of articles debunking the most common myths.
Myth #1: Green Roofs Leak, and Often
Because many green roofs require irrigation and drainage, one of the most common misconceptions is that they can leak, and when they do they leak a lot. Although there are cases where vegetative roofs have leaked, especially shortly after installation, whether or not a roof will leak has nothing to do with it being a green roof. In other words, traditional roofs are just as susceptible to leaking, and there is no evidence that green roofs have more of these issues. In fact, more evidence supports just the opposite.
Because the additional layers of vegetation and soil cover the waterproofing membrane of a green roof, it is protected from UV light and therefore receives less UV damage over time. Those additional layers also protect the membrane from hail, wind, and storm damage. This is why green roofs often last up to, if not more than, twice the lifespan of a traditional roof. Also, many green roofs have an additional protective barrier that keeps roots from digging too deep.
One of the reasons why some green roofs do leak is that the membrane was damaged during construction or that the seal between the membrane and the drains are not adequate. Green roofs DO require irrigation and drainage, so it’s important to make sure that during installation, the membrane is installed correctly. Many cities with green roof legislation like Denver, require leakage tests to prove the membrane is waterproof.
When performing maintenance, it is also crucial to make sure that any digging or tilling of soil does not damage the waterproofing membrane. Often when getting a green roof installed, the first few years of maintenance (what we in the industry call the establishment period) is included in the budget and done by a professional contractor or landscaping team that is familiar with the system and won’t damage it.
So there you are! Leaking is not a problem specific to green roofs. As with any project, correct installation and maintenance are key in keeping any issues at bay. That’s one myth debunked, stay tuned for our next article in this series!