Green roofs are an extremely practical and beautiful concept. Not only does it allow the use of unusable space. For roof gardens add value to your property and surroundings in many ways. When designing a green roof, you are only limited by your imagination. A roof garden in the form of a lawn is not enough? How about a mesmerising plant composition? Decide for yourself!!

What is a green roof?

A green roof is a layer of vegetation on top of a building's waterproofing system. Vegetation can overgrow the entire roof surface or only a selected part of it. Green roofs, also known as vegetated roofs or eco-roofs, are classified according to the type of greenery used, the degree of slope, the thermal insulation layer and the adaptation method.

Where a rooftop garden can be installed?

A green roof is the solution that is most often used where a classic single-storey garden cannot be arranged due to lack of space. In principle, a roof garden can be created anywhere: on the roof of a detached house, a garage, a summerhouse, a public building or even a dumpster. However, it's worth paying attention to the important elements already at the design stage. First and foremost, the roof structure must be strong enough to bear the weight of the plants, soil and insulation.

Green roofs - types - breakdown by type of greenery used

The basic division of green roofs into extensive and intensive green roofs, in terms of the type of green used, refers to the thickness of the substrate layer, which determines the applicability of the cultivation. This has a bearing on the strength of the entire building structure and its ability to take up the loads involved;
✔️ extensive green roofs - also referred to as eco roofs or green floors - are characterised by shallow green roots, with a substrate layer of 2 to 20 cm. The total additional load on the building structure is relatively low and can range from 50 to 170 kg/m². Extensive roof cultivation with a small substrate layer thickness determines the selection of low-demanding plant species and a shallow root system;
✔️ intensive green roofs - known as roof gardens by design - are intended to resemble a traditional garden and are a more demanding and labour-intensive green roof technology. The roof structure for an intensive roof must be able to withstand significant loads, which can reach from 200 to as much as 970 kg/m². Intensive roofs are also utility roofs. This is because they can house the entire garden infrastructure with fountains, pond, benches, gazebos and even swimming pools. The costs for this type of roof are necessarily higher than for an extensive roof. However, the functional and visual qualities effectively compensate for this, adding to its attractiveness.

Which plants for a green roof?

The choice of plants for a green roof depends on many factors. First and foremost, whether the established roof is intensive or extensive. The climate, the composition and depth of the substrate, the surface area, height and pitch of the roof, the load-bearing capacity, the presence or absence of an irrigation system and our expectations regarding maintenance are also among the defining criteria. For light extensive roofs, it is advisable to use species that are easy to grow, drought resistant, do not require special maintenance and that generate a root system that is not too deep. Seed mixes that include grass and herb seeds or sedum stems in their composition will therefore work perfectly. An extensive roof garden can also be created using flowering plants (camomile, thyme) as well as plants such as mosses, yarrow, dioecious yarrow, Caucasian dogwood, woolly purple loosestrife or cephalopod. When it comes to the selection of plants for roofs in intensive culture, there are no major restrictions. Ornamental grasses, perennials, herbs and low shrubs are recommended for low-intensity greening. Intensive high vegetation is mainly used on the roofs of public buildings and modern blocks of flats and is mainly trees and shrubs.

Green roof structure

A properly constructed roof garden consists of several layers:
✔️base - depends on the type of property on which the garden is being established. This is most often a floor slab or wooden structure;
✔️ waterproofing layer - is a guarantee of waterproofing and resistance to root penetration;
✔️ protective layer - additional protection of the waterproofing against damage (mechanical, roots and damage caused during use);
✔️ drainage layer - responsible for draining and storing water. It is also an additional space for plant roots;
✔️ filter layer - protects the drainage layer and deeper layers from contaminants, and is resistant to rot;
✔️ vegetation layer - a substrate that is selected to suit the plants that will be planted on the roof, yet is lightweight and unencumbered by the structure;
✔️ plants

Roof garden - benefits

Green roofs have a wealth of positive features. The most important benefits of a building with a roof garden include:
✔️improving the ambient microclimate - by reducing carbon dioxide and releasing oxygen;
✔️purifying the air from dust, fumes and pollutants;
✔️ building attenuation - green roofs are excellent at attenuating noise, especially low frequency sounds - visual attractiveness of the surroundings;
✔️ rainwater management - green roofs can retain up to 90% of rainwater during the summer season;
✔️ thermal insulation of the building - vegetation on the roof is a natural yet effective barrier against overheating and excessive cooling of the building.