Green Roof Gardens
The development of ‘green’ roofs is occurring more often in order to enhance the beauty of roof tops. Besides the moss-sedum roofs originating from Norway there is substantial demand for genuine roof gardens containing trees and shrubs. However, not all roofs are suitable for a roof garden construction. The roof must be able to carry the weight of the soil and plants. Fytodak Europe B.V. is introducing a lightweight roof garden system called Hydrocell® RG30 onto the market. This system may be laid-out on almost all flat roofs.
Interesting for architects, construction engineers and property developers is that it is possible to use this system on light roof structures. A roof garden creates a more pleasant living and working climate. In addition to this, a roof garden prolongs the life span of the roof covering. Hydrocell® is the ideal substrate for every roof garden laid outside or on balconies due to the large capacity to retain moisture.
Development of Hydrocell® RG30 roof garden system
Hydrocell® RG30 is a foamed aminoplastic resin. Approximately 1.6 million m2 of roof gardens have been laid out in Western Europe during the 40 years that this foam has been on the market. Furthermore, it has a very long life span. With a heavy rooting development and without maintenance the life span can reach up to 25-30 years. This is approximately the write off period maintained by property developers for the construction of a roof garden.
The advantages of Hydrocell® RG30 in a nutshell
- High compressive strength.
- Empty space percentage amounts to 80% as a result of the open cell structure.
- Very durable and solvent-proof even under extreme climate conditions.
- Hydrocell® RG30 applied in a layer of 10 cm, has a water absorption capacity of max. 80 litre/m2 (80 vol%).
- The water absorbed will be supplied gradually and completely to the plants which grow with their roots in the hard foam. This in contrast with poly-acrylamides, expanded clay or lava which are buffering quite a lot of water, but supply only a small part of it to the roots.
- A safe and suitable system for architects and developers.
- No further maintenance of the system after installation and therefore profitable.
- Self water regulating throughout the year.
The Hydrocell® RG30 layer functions in combination with the root resistant cloth as a filter, which prevents small particles seeping through towards the drainage layer. As a result of this silting up of the Fytonop slabs will be prevented.
Minimum Roof Load
Fytodak’s roof garden system is on a whole very light in comparison with other systems. Due to this roofs with a lighter structure may also be considered when planning a roof garden. The newly implemented Hydrocell® RG30 layer with a thickness of 10 cm weights approximately 11 kg/m2. This weight will be approximately 88 kg/cm2 when this layer is completely filled with water (max. 80 vol%). The soil which is building up the top layer will be mixed with foam flakes so that the specific weight decreases with 35% to 50% with respect to normal soil (depending on the mixture). Mixing soil with foam is not only advantageous for saving weight, the addition of flakes to the soil also results in an ideal air-water management which in turn will stimulate a better rooting development.
Laying out a complete package is a highly specialised job, in particular because the roof covering may not be damaged. Firstly the LDPE film is installed with the Fytonop drainage cell hereon. Secondly the root resistant cloth. Now the foaming with Hydrocell® RG30 foam can begin. After the application the foam layer has to harden for a couple of hours. The finishing touch will be the application of the lightweight soil package. The roof garden is now ready for planting.
It is often difficult to attain a good water management. Very wet periods with an abundance of rain are often followed by long periods of drought.
Generally speaking roof gardens are very sensitive for these fluctuations. However, by means of the Fytonop drainage cells, the excess rain (-water) is drained off at a rate of 20 litres water per second/m2. The required 80 litres water remains absorbed in the Hydrocell® RG30 substrate layer.
The Fytodak system is ideal as subsoil for moss-sedum, herbs and grass vegetation mats. These mats are a good alternative for e.g. gravel roofs. The great advantage of moss-sedum mats is the immediate visibility of a colourful green carpet after laying.
Everything we install in our environment has to be checked in accordance with its biodegradability. Hydrocell® RG30 foam is biodegradable because it degrades by means of hydrolysis within a period of 30 years to nitrogen which in turn functions as a fertiliser for plants. Hydrocell® RG30 foam can also be reused for thermosetting plastic products like e.g. wall sockets.
The complete package
The overall package consists of three modules:
- Fitting the roof insulation and roof covering
- Laying the entire substructure of the Hydrocell® RG30® roof garden package
- Delivery of planting schemes and soil mixtures.Many architects opt for this entire package with one central communication point. Total responsibility is put into the hands of Fytodak Europe B.V. instead of three different parties. Fytodak Europe B.V. will also advise on the different options.
Hydrocell® RG30 is the ideal substrate for every outside roof garden or balcony due to its capacity to retain moisture.
A Hydrocell® RG30 roof garden construction consists of (from up to down):
- Light weight soil packet (25 cm thick) of 40% foam flakes and 60% soil
- A Hydrocell® RG30 hard foam layer
- Root resistant cloth
- Fytonop drainage cell
- LDPE film.
Both trees and higher growing vegetation are able to root themselves in an excellent way into the Hydrocell® RG30 layer. In general trees will only be anchored during planting until they have attained a robust root system.