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Green roofs by De Boer Green are the fruit of know-how and craftsmanship.

We are rooted in De Boer, a company which has been making superior waterproofing membranes for roofs since 1922. We care about the environment, about energy awareness and about sustainability.

Xeroflor® is our premium partner for green roof vegetation. They have been developing their system of lightweight, pre-vegetated mats since 1972.

The famous architect Le Corbusier once remarked: “Isn´t it against all logic, if a whole urban surface remains unused, missing the dialogue with the stars?” With this in mind, we aim to make your roof green.

GREEN ROOFS: WHAT AND WHY?Green roofs are pretty, environmentally-friendly and economical. They create a nicer environment to live in. Sunbathing in the city, catching a breath of fresh air during work, or just generally enjoying nature even when in the center of a busy city: green roofs make it possible. Roofs protect us from the elements. While a plain roof may meet this requirement perfectly, more is possible, e.g. by going for a “green roof”.

A green roof is mostly covered with living plants. The name “green roof” may be a bit misleading, though, as the roof as such doesn’t have to be green, nor do the plants which are cultivated on it.

Vegetation cannot simply be planted on the roof. Green roofs require a proper base with an appropriate structure, a suitable growing medium and proper drainage.

In principle, you could let nature follow its course. Only, it is likely to take ten to twenty years before you get the desired effect. It’s better to give nature a hand by opting for a proper green roof with pre-vegetated mats.

ECONOMIC BENEFITS Green roofs …• improve water management (retention capacity, less risk of

flooding,...);• cool (especially during Summer, your building will remain cooler;

you will, therefore, save on air-conditioning costs);• are sound insulating;• extend the lifespan of the waterproofing membrane (thanks to

the vegetation, the membrane is less exposed to UV rays, to the weather, etc.);

• save space and use otherwise unused space;• promote recycling (good to know: most components of our green

roof systems result from recycling).

ENVIRONMENTAL BENEFITS Green roofs …• improve the air quality;• the air is much purer on a green roof. That’s normal, considering

that the vegetation produces extra oxygen and filters the fine dust particles;

• reduce the warming in built-up areas;• have you ever heard of the “urban heat island effect”? Even if you

haven’t, you will certainly have felt it: in cities, temperatures are higher and the air is dryer. That’s where the vegetation on green roofs comes in: it lowers the temperature and the evapotranspira-tion makes the air less dry. Indirectly, lower temperatures reduce the consumption of energy, the use of fossil fuels and the emission of CO2. In short: a better air-quality;

• increase biodiversity in cities;• the more green roofs there are, the more vegetation there is and

the more animal diversity there is. Green roofs bring nature back into the cities.

AESTHETIC BENEFITSGreen roofs …• make for a pretty investment;• add an extra floor to your building; • are eye-catchers which is also commercially appealing;• it’s clear that plants appeal more to people’s imagination than a

plain grey or black roof would ever do.

There are two big categories of green roofs. The German FLL (Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau e.V. or Landscape and Landscaping Development Research Society) distin-guishes green roofs based on the required level of maintenance:

• intensive greening: creates a roof garden which is comparable to a garden at ground level, both in use and in the required mainte-nance;

• extensive greening: the green roof is low-maintenance but access is limited or even ruled out

In between these two categories, there is also semi-intensive greening. One cannot say that all green roofs are roof gardens. The opposite does hold true: all roof gardens are green roofs. A “roof garden” is a green roof which has the characteristics of a garden, but which is situated on a roof. Why opt for a green roof?

• a green roof is so much prettier than a conventional roof;• environmentally-friendly: green roofs reduce the pressure on the

sewage system, they reduce the risk of flooding, they have a cool-ing effect, etc.;

economical: investing in a green roof will help you save money. Not only will the waterproofing system on your roof last twice as long, you will also benefit from government grants.

OUR SYSTEMSWhen considering which type of green roof to install, you first of all need to consider the physical and technical characteristics of your building. The maximum installation height and the maximum load of the roof structure will determine the thickness of the substrate and, thereby, the choice of vegetation.The latter also depends on the roof’s orientation and on the level of maintenance you are looking for.

OUR COMPONENTSDrainage

Our DBGS DRAIN 8 is a three-dimensional mono-filament structure which consists of two filter fleeces with a mat of polymeric entangle-ments with large cavities in between. The layers are thermally bonded to one another.

Because of its specific construction, DBGS DRAIN 8 fulfils three roles: • it drains any excess water;• it protects the underlying waterproofing membrane from mechan-

ical damage;• it filters the small substrate particles, avoiding any clogging of the

drains.

Water-retaining layer

In order to achieve sufficient water retention, we sometimes put water-retaining geotextile or mineral wool on top of the drain mat. Whether this is needed or not, depends on the chosen vegetation, on the maximum installation height and on the roof load.

Growing medium This is the layer in which the vegetation roots. As such, it is the vital component of the green roof system. It consists of either a mineral substrate or a water-retaining layer.

As the plants’ nurturing ground, the substrate most not only have the right physical, chemical and biological composition, it must also have proper ventilation and water management.We determine the thickness of this layer based on the intended vegeta-tion. The larger the plants, the thicker the substrate layer will need to be

Vegetation layer

In the case of intensive greening, there are hardly any limits: flower beds, a lawn, shrubs and even trees. Extensive greening is limited to sedum, moss and sometimes herbs.

Attention: plants which root aggressively or plants with tap-roots are not suited for green roofs.

INTENSIVE GREEN ROOFS

Wouldn’t it be wonderful to turn your roof into a real living area ?

This is perfectly feasible. Indeed, unlike extensive green roofs, intensive green roofs are meant to be walked upon. In fact, you can use them for various recreative purposes.

An intensive green roof requires maintenance similar to the mainte-nance of a traditional garden. Of course, the building’s design needs to cater for the thick substrate layer.

But, then, the “land” used for your garden comes for free. A big saving, bearing in mind the high and ever increasing price of land.

De Boer Green has developed two standard systems for intensive vege-tation. We can easily adjust them to your project’s specific requirements.

DBGS-I-HIGHRoof pitch System configuration Maximum roof load Construction height

1-6° DBGS drain 8 450 kg/m2 - ... 31cm - ...

possibly an additional water retention layer (may be indicated when extra water buffering capacity is required)

Xeroflor XF 203 (min. 30 cm) in accordance with RAL

an almost unlimited choice of plants:a range of ground cover plants, ornamen-tal grasses, perennials, higher types of shrubs, small trees or a traditional lawn.

DBGS-I-MEDIUMRoof pitch System configuration Maximum roof load Construction height

1-6° DBGS drain 8 300 - 450 kg/m2 20-30cm



a range of ground cover plants, ornamental grasses, perennials, most lower shrubs or a traditional lawn.

CONSTRUCTION1st layer : drain mat2nd layer : mineral substrate3rd layer : vegetation

EXTENSIVE GREEN ROOFSThese low-maintenance vegetation systems are suited for (low pitch) roofs (1-35°) with a normal exposure to the sun, rain and wind and which are seldom walked upon.

Advantages:• requires little maintenance;• limited choice of vegetation;• not meant to be walked upon, except for maintenance;• the least demanding from a building-technical perspective.

Functional characteristics

• aesthetic: permanent vegetation, which changes with the seasons and with the sunlight;

• florescence from May to August, depending on the species;• slow-growing plants, requiring little maintenance, pruning or

mowing;• plants which resist well to drought: watering is not needed, unless

just after planting or in the event of exceptional drought (longer than 6 weeks);

• acts as a rain water buffer (depending on the system up to 34 liters per m² and 50 % of annual rainfall); in the case of heavy rain, less water goes into the sewage system, and the water that does, does so much slower;

• protects the waterproofing membrane against UV rays, thus significantly increasing the membrane’s lifespan;

• protects the building from the sun during Summer: this natural cooling reduces the energy consumption of the air-conditioning system;

• retains the dust particles in the air;• insulates against air nose and contact noise (rain or hail);• enhances bio-diversity (birds, bees, butterflies,…);• maintenance is limited to removing unwanted vegetation, fertilising

and, if needed, extra sowing. Once or twice per year, depending on how the vegetation develops.

SEMI-INTENSIVE GREEN ROOFS

Although this “light roof garden” does not have a very thick substrate lay-er, it does offer lots of possibilities to create an aesthetic unity.

By opting for a semi-intensive system, you combine the benefits of exten-sive green roofs and the benefits of intensive green roofs:

• a wider range of plants can be used (ground cover plants and ornamental grasses);

• accessible;• requires little maintenance;• less structural demands than with intensive systems.

Regular irrigation is, of course, needed.Our range comprises species and varieties which are adapted to the specific environment of your roof:

• ornamental grasses: Festuca spp., Penisetum spp, Imperata spp., … ;• ground cover: Vinca spp., Hedera spp, Pachysandra spp., …

DBGS-I-LIGHTRoof pitch System configuration Maximum roof load Construction height

1-6° DBGS drain 8 180 - 285 kg/m2 13-20cm



range of ground cover and ornamental grasses

1st layer : drain mat2nd layer : mineral substrate3rd layer : vegetation

CONSTRUCTION

Roof pitch System configuration Weight, saturated Thickness

1-10° DBGS drain 8 90 kg 70 mm

Xeroflor XF 200 (40mm)(in accordance with RAL)

Xeroflor XF 317

PRE-VEGETATED MAT ON SUBSTRATEThis system is used when immediate result is required and when the roof can take a load of at least 90 kg/m².

CONSTRUCTION1st layer : drain mat2nd layer : mineral substrate3rd layer : pre-vegetated mats



Xeroflor XF 200 (60mm)(in accordance with RAL)

Xeroflor XF 304

SEDUM CUTTINGS SOWNON SUBSTRATEThis system is used when immediate result is not required and when the roof can take a load of at least 100 kg/m².

CONSTRUCTION1st layer : drain mat2nd layer : mineral substrate3rd layer : sedum cuttings



Xeroflor XF 107

Xeroflor XF 317

PRE-VEGETATED MAT ON WATER-RETAINING ROCKWOOLThis system is used when the roof is not very accessible or when it cannot take a high load.

CONSTRUCTION1st layer : drain mat2nd layer : water-retaining mineral wool3rd layer : pre-vegetated mats


1-35° (*) Xeroflor XF 154 / 159 30-45 kg 30 mm

Xeroflor XF 300 / 301

(*) 30° pitch only if the roof is not facing south.Depending on the pitch, the configuration may be adapted and an irrigation system may need to be considered

PRE-VEGETATED MAT ON WATER-RETAINING GEOTEXTILEThis system is used on roofs with a pitch of up to +/-35° (when not facing south or south-east).

CONSTRUCTION1st layer : one or two layers of mechanically nailed geotextile2nd layer : pre-vegetated mats

MAINTENANCESeveral factors influence the quality and the lifespan of a green roof. For instance, if certain components are wrongly selected, dominating plants may start overgrowing the green roof.

Climate conditions can be important, too. Sedum requires at least three hours of sunlight during the Summer. When periods of drought last for more than 5-6 weeks, irrigation is needed. Other species thrive better in shadowy areas or can withstand longer periods of drought.

Design and maintenance require attention, as well. Do bear in mind the following:

• choose the right substrate. A wrong choice of substrate, or the wrong composition, increases the likelihood of undesired vegeta-tion developing. The share of organic matter must be adapted to the vegetation;

• determine the water-retention capacity needed for the vegetation. Too high a water-retention may prove disastrous as undesired vegetation would develop lavishly;

• execution of roof details. You would want to minimise the risk of (unwanted) vegetation damaging roof details.

As soon as the vegetation has been put on the roof, you need to fertilise it using an organic fertiliser, and you need to irrigate it adequately.

Whatever the type, all green roofs require maintenance.

Extensive green roofs: low maintenanceContrary to other types of green roofs, extensive green roofs require only little maintenance. However, that does not mean that no mainte-nance is required at all. During the first year, we recommend to control extensive greening each quarter. From the second year onwards, one yearly inspection should suffice. In the first two years, maintenance can take place in Spring and in Autumn. Afterwards, one maintenance session per year, in Spring, should be enough.

• remove parasitic plants with roots and all;• replace dead plants and sow bare spots;• check on erosion in the substrate (on sloping roofs);• remove waste, such as dead leaves which have piled up;• in case vegetation mats would have shifted: put them back in place;• check all roof details.

Intensive green roofs: same level of maintenance as an ordinary garden

Until recently, vertical gardens were still being associated with prestigious projects in the likes of New York and Paris. But green walls and façades have gradually become more mainstream. In Belgium and Luxembourg, for instance, many vertical gardens now adorn the walls or façades of new or existing buildings.PlantDesign is market leader in Belgium and Luxembourg in the design, the execution and mainte-nance of vertical gardens. Since its creation in 2007, PlantDesign has completed already more than 200 remarkable projects, including a number of certified state-of-the-art (HQE, BREEAM, DGNB) projects which put sustainability at their heart.

CUSTOM-MADE GREEN WALLS

You decide; we will translate your creative ideas into green walls, whichever their location and which-ever their shape. Together, we will develop a solution that meets your requirements and desiderata. That may be a vertical façade which turns your building into a real eye-catcher, or it may be a green wall which turns your reception area or your living area into a haven of tranquility. Vertical gardens do not only appeal to the eye, they also create a working and living environment which is healthy to body and soul. TECHNOLOGY AND NATURE UNITED

PlantDesign uses a non-soil bound modular system called the Plantbox. Plants are put in separate modules, which are independent of the wall, the façade or the soil. We use sphagnum, a substrate which can absorb up to 20 times its own weight in water, resulting in efficient and economical water irrigation. With our long experience and knowhow about plants and about state-of-the-art automated irrigation, we put in place reliable and durable systems.

With our maintenance contract, you can always enjoy the green beauty of your vertical garden.

SHARE OUR GREEN PASSION

DE BOER GREENMetropoolstraat 33B 2900 SchotenTel. +32 3 641 08 [email protected]