If you want to create an amazing garden on terrace, then it is essential for you to understand about the Terrace/Roof garden construction.
Roof garden construction can be done by three methods: First method is to make a container garden on terrace, second one is to make a lot of raised beds to grow plants, either permanent made of concrete or wooden. The last and third method is to make your whole roof or some selected part, a vegetation ground like a regular garden. This educative article is based on this third method: It has five layered structure, you’ll see below in this step by step guide.
New building’s roof construction, (*if planned to used as a garden) is usually made by invert roof system (in comparison to the conventional system where the waterproofing is laid above insulation layer), in this the waterproofing is arranged under thermal insulation.
With this arrangement, the roof waterproofing remains protected from mechanical damage and against the direct influence of external factors (temperature, UV radiation, wind suction forces etc.). In addition, the temperature on the waterproofed surface remains stable regardless of whatever the weather conditions are.
1. Waterproofing Layer
Roof must be waterproofed, durable and frost resistant, if you’re growing plants on it, whether you will grow plants on containers, raised beds or on the roof itself, roof waterproofing is must and should be the first step of terrace garden construction as it protects the roof from leaking.
Waterproofing covers up the entire surface of the roof, most importantly those spots where the plants will be planted.
2. Insulation Layer
Insulation layer (Protection Layer) makes a terrace garden resistant to moisture and temperature fluctuation and provides it sufficient mechanical strength. It is made mostly of XPS extruded polystyrene boards, PIR panels or polyurethane foam.
PIR panels are well suited as a layer of insulation on the roof garden as they have special grooves and milled edge connections that allow rainwater to pass to drainage systems easily.
3. Drainage Layer
Drainage layer on the roof garden is used to quickly discharge the rainwater from the vegetation layer into the drainage system, as well as to collect excess water.
To read more on drainage for terrace garden, read this article.
4. Geotextile Layer
Geotextile fabric layer is used to separate drainage layer and plants growing in soil. It prevents depositing of soil and other fine particles that clogs the drainage system.
It also counteracts the reduction of water rapidly from the vegetation layer by circulating the moisture.
*Geotextile should be waterproofed and vapor-permeable, chemically and biologically resistant and mechanically robust.
5. The vegetation Layer
Vegetation layer means the growing medium (soil), the surface where you’ll grow plants and greenery. Growing medium should have good air circulation and it should have to be water permeable. Soil is preparation is done according to the plants you’re growing. Generally plants require fertile and slightly acidic soil, which can be prepared by mixing garden soil, humus, farm manure or compost and organic matter.
Thickness of the growing medium depends on the type of the plants you will grow in it.
Plants you can Grow
Roof area can be used to create decorative vegetation, or edible garden or to create a low maintenance garden. The rooftop garden is sufficient to grow various forms of vegetation: shrubs, grasses, annuals, perennials, herbs, vegetables and even dwarf fruit trees depending on what you wish to grow, climate, budget, available space and the functioning of the building.