Construction aspects of green roofs

Today, in Gardenprue,  we are going to talk about a topic that is currently on the lips of many unfortunately (due to the case that we will tell you below), plant covers . A totally modern design in which “living” materials are used to define construction solutions. All very nice yes, but you also have to take into account some considerations, to avoid scares and problems. Let’s see it. 



The green roofs or roof gardens , are colonizing many terraces and coronations of the buildings that are made today, returning the green space that existed or could exist before construction. Being able to enjoy green spaces on your own rooftop is a luxury that is increasingly within our reach.

But for this we must bear in mind that not all the terraces of our buildings are prepared to support the great weight that this type of plant roof provides: the species, the substrate that is required and especially the water for irrigation increases the weight significantly. (Remember that the weight of wet earth can reach 1,700 kg / m3) and even more so on those rooftops where we find swimming pools. A good calculation is essential and essential for the success of the structure that will come to house this type of roof. It is no joke to dismiss this point since the consequences can be catastrophic in some cases: unfortunate facts of not taking this concept into account we found it recently in thecollapse of the roof of a shopping center in the Latvian capital, Riga, due to, according to the hypotheses, the extra loads to which the structure was being subjected when building a green roof for which it was not calculated; a new building barely two years old whose structure was not prepared to receive such an increase in weight collapses to the amazement of everyone.

A poorly executed green roof could be the cause of the collapse of the roof of the supermarket in Riga


The shape of the roof structure also gives rise to different and distinct perceptions of the green roof: a horizontal structure provides a walkable green roof , which allows its maintenance and the cultivation of a rich variety of vegetation that can be worked with and on which can be easily accessed; Instead, a sloping structure creates green roofs that are more for visual and aesthetic enjoyment where grass is the king of the species chosen for cultivation because it is a type of vegetation that adapts very well to green roofs and can grow easily.


Up to three types of green roofs can be distinguished according to the type of plant variety, the maintenance and the thickness of the substrate.

First, the extensive green roof requires minimal maintenance for vegetation that is planted in up to 15 cm thick topsoil, such as grass.

In second place we find the semi-intensive green roof, with a medium maintenance and with a thickness of between 15-30 cm where medium-sized shrubs can already be grown.

Finally, the intensive cover requires higher maintenance for the larger plants and shrubs found in the up to 50 cm of topsoil that it can accommodate. We have to emphasize once again the resistant capacity of the structure for these roofs in general and specifically for those of this type, for example.


Not only the green aesthetics is the attraction of this type of roof, but the insulating power that it exerts towards the interior of the building is very high, being able to equate to the insulation values ​​of a thermal insulation panel without having anything to envy in this aspect. . The only downside: the great thickness that the green roofs require compared to the panel, but yes, the enjoyment that the first one can produce and the activities that can arise in the garden roofs are unrivaled.


The basic pillars for the proper functioning of a green roof are: the waterproofing of the roof (to be taken into account in weak points such as in the encounter with a drain), the drainage and evacuation of irrigation water and, once again, the suitability of the structure. It is also recommended to use anti-puncture geotextiles under the substrate layer that allow a separation between it and the draining layer and also avoid possible fractures of the impermeable layer due to root growth, which could cause annoying leaks in the spaces located under the cover. These geotextiles are totally porous, so there is no water pocket of any kind.

In the event of a possible leak, repairs are usually more tedious due to the task of uncovering the area of ​​the damaged waterproof sheet and moving the substrate aside to be able to work on it as the repair process itself: this specific problem can be solved by superimposing a new waterproof sheet on top of the affected area and applying heat so that they work as one.

You already have more information so that, when you see some plant covers , you know all that this entails, advantages, disadvantages and the possibilities that you can find in this small world.

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