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Landscape green roof

13 min read
Landscape green roof

A beautiful park landscaped on the top of the roof can really delight our eyes and souls. This kind of intensive green roof is spectacular indeed, has a high decorative value and can incorporate all landscaping elements (aisles, streams, alpine gardens etc.). These gardens beautify the environment, add value to everyday life, offering not only visual satisfaction and physical relaxation but bringing lots of benefits too.

In urban areas, a landscape garden is like a small paradise above a busy, noisy and polluted city. In such a landscape project, we can have multiple possibilities: we can build Japanese gardens, English gardens, places mirroring nature in its own wildness, using native plants along tinkling streams, so everything is possible if some important criteria are considered before the landscape starts.

For our own safety, some technical and legal issues must be taken into account:
In case of new constructions, the design of the structure must comply with the regulations in force.

For existing buildings is necessary a technical expertise in order to evaluate the existing safety level and after the green roof is installed. The expertise regarding earthquake safety must be performed according to the terms of Code P1003/2009 by inclosing the building in one of the four seismic risk classes.

If the construction meets the required parameters, as these systems can reach even 700 kg/m² because of the thickness of the substrate, we can start planning our landscape roof.

At this stage we can also follow the client’s preferences regarding the landscape elements, and the role of our intensive green roof in the whole architecture of the building. For example, vegetation can also offer certain privacy to neighbouring constructions by planting perennials, shrubs or trees at the edges. This kind of vegetation can also provide some soundproofing.

The most important role of a landscape roof is to provide a space for recreation, relaxation, and why not for entertainment. So, an adequate maintenance must be ensured (possibilities for irrigation and a long-term budget).

What is your dream about a perfect landscape garden? Everything is possible; the limit is only our imagination and the budget we can allow! 7 m high trees, ponds, ornamental rocks with vegetation, different species of plants and flowers adapted to climatic changes: all these can offer a colourful show all year. We can also include garden furniture, pergolas, swings, and the list could continue…

The technology used for a landscape roof is similar to a standard green roof, especially the intensive one. Drainage and moisture retention must be effective in order to ensure the high humidity need of such vegetation.

Every project has its own characteristics depending on the microclimate, emplacement and the landscape project, still we can enumerate some general steps:

The protection and closing layer is at the basis of the living roof and is made of a membrane against roof penetration.
Another protection layer follows, which is a geomembrane of polyester fibres or a mixture of mechanically consolidated fibres, polyester and regenerated polypropylene, and a water retention capacity of 3-6 l/m², depending on the product.
The next layer of drainage boards is for water retention, having the same role as the gravel course, but with superior properties (the gravel does not have water retention capacity because of its high weight, etc.). These boards are 50-80 mm high, retain water and direct excess water toward overflow gutters. Depending on the model, drainage boards can retain 10-21 l water per m², having just 2-4 kg/m². The intensive green roof bears pedestrian traffic too, drainage boards are resistant to compression between 25 kN/m² and 35 kN/m².

A 1-2 mm thick polyethylene cover which forms the filtration layer and prevents clogging or filling of drainage layer with fine particles from the substrate or the vegetation layer.
In some cases, the irrigation system and the lighting system wiring is installed.
The vegetation layer, the space for roots is essential to the survival of plants. In case of landscape roofs, the thickness of the vegetation substrate is about 400-1000 mm, according to weather conditions and the vegetation type. It is composed of recycled and organic materials, like split face natural tiles, perlite, pumice, volcanic clay, peat fibre, biodegradable fibres, in granule forms of 1-40 mm. The most important features in case of the substrate are: the water retention capacity, which can vary between 25 and 40 %, the permeability and the stability of the structure.

In fact, the vegetation layer is similar to one on the ground, for example rich in plant species. Of course climate and microclimate, plants’ annual growth rate are very important and must be considered. It’s recommended to use native species of perennials or annuals, shrubs, vegetable plants, fruit-bearing shrubs etc. In case of woody plants, conifers and hardwoods, some features must be followed: undergrowth and shrubs, maximum height of 5-7 m; creeping or erect stems; to be adapted to drought (xerophile, xero­-mezophile species) and to be resistant to frost. Trees must be suitably anchored, so that their centre of gravity to be placed as low as it’s possible, without risking their displacement by a strong wind (there exist special anchoring devices – see section Elements of green roof systems). The landscape project must be realized in accordance with the project of the green roof’s structure. For example, a common formula is: height growth/10 = constructive thickness of the substrate. Such an intensive green roof is higher than 45-150 cm, its water retention capacity is about 30­-150 l/m, and its surface weight is between 300­-700 kg/m². Of course, these values are only indicative, they can be influenced by the conditions of the landscape project.

Maintenance of an intensive green roof is performed in two stages:
Maintenance after plantation, which can last about 2 years. This period is actually the consolidation of the vegetation.
Maintenance during service time of the green garden. This includes all steps which would be done in a garden on the ground level with the same landscape structure. It’s very important to ensure the continuous moisty of rooftop gardens, to use fertilizers with slow release and to keep them compact, especially plants with high growth rate.

Building an intensive landscape roof can last a few days, but also a few weeks. Its maturing may take one-two years, which needs a bigger initial investment and a certain budget for the continuous maintenance. But the satisfaction brought by this floral micro universe is peerless… and it’s possible to achieve.

Our expert team offers consultancy to build green roofs and terraces, landscape roofs, parks on the top of buildings, green projects that please the eye. Intensive green roofs are really spectacular, have high decorative value and can include all elements of a landscape project.

We are at your disposal with turnkey projects and long-term maintenance. We use reliable building materials, plants especially developed for rooftop gardens and high quality vegetation rolls. Every landscape work offers the best cost/effectiveness/safety balance and every project is adapted to our customers’ aims.

We are able to landscape green terraces, intensive or extensive green roofs on the top of industrial halls, inside or outside vertical gardens for office buildings, and intensive green gardens with special relaxing zones, landscape green roofs with pedestrian traffic for shopping malls and many other ecological constructions.

To increase the ecological value of the building, photovoltaic panels can be also installed.
We are happy to help you with green projects, system solutions, estimates, and consultancy in the field.

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