Introduction to Roof Gardens

The concept of roof gardens, also known as green roofs, has been around for a long time, dating back to when roofs first existed. In simple terms, a roof garden refers to a green space on the top of a roof. This green space can be implemented on the roof of a building or in a courtyard. Planting beds are placed on an artificial substrate on the roof’s surface. A roof garden, also referred to as “Bagh-e Bam” in Persian, offers an opportunity to bring the beauty of a garden to your urban space, maximizing your landscape views. Today, advancements in technology have made it possible to create beautiful gardens with various plant varieties on the roofs of houses and tall buildings.

In recent years, city dwellers have sought to make use of roof gardens for planting. As a result, roof gardens or green roofs have become a relatively common idea. Regardless of the size of your space, people always crave more greenery.

Today, the construction of various types of roof gardens in unused spaces on the roofs of office buildings, commercial buildings, and residential buildings has become a common practice.

2. Intensive Green Roofs

Intensive green roofs require a minimum growing medium depth of 30 centimeters. They offer the flexibility to grow any type of plant cover. In a saturated state with water, intensive green roofs add an additional load to the structure ranging from 300 to 700 kilograms per square meter. Therefore, it’s essential to calculate the extra load on the building during the design phase. The advantages of intensive green roofs include the freedom to choose any type of plant and design flexibility. However, they come with higher installation and maintenance costs and may not be suitable for structures that are not robust.

Key considerations during implementation include:

• The choice of suitable plant cover, taking into account factors like heat tolerance, direct sunlight exposure, and root growth.
• How the rooftop green space will look, including plants, planters, and bushes.
• Automatic irrigation system, Preservation and maintenance of plants in the form of irrigation over a period of time is specific to the automatic and intelligent drip irrigation system.

The lighting design for the rooftop green space is essential, as it significantly affects the overall aesthetics. However, it can be a higher-cost element in roof garden design.

The standard roof preparation is done according to the modular method. Preparing the rooftop surface according to this method is vital.

Flooring of Rooftop Spaces Roof garden flooring can be implemented in three forms: wood, sand, and decorative stone tiles. The more extensive the surface area of the flooring, the higher the cost.

Ancillary Equipment for Rooftops Atriums, pergolas, gazebos, fountains, furniture, and other spaces such as barbecue areas and outdoor kitchens are considered part of the ancillary equipment for rooftops.

Please note that a low-cost implementation of roof garden design may imply low-quality results. Therefore, it is essential to use ideal materials in the execution of a roof garden or green roof to avoid higher costs later.

Considerations for Green Roof Implementation The methods and details of green roof implementation can vary greatly from country to country due to the competitive nature of the industry. However, a green roof typically consists of six main layers:

1. Moisture Barrier: The roof surface should be well-insulated to prevent moisture infiltration. Green roofs can be installed with any type of moisture barrier. The choice of moisture barrier does not limit the specialized team, but factors such as installation cost, barrier lifespan, and environmental concerns need to be considered. Bitumen insulation and isogam are the most commonly used moisture barriers in Iran.

2. PVC Waterproofing Membrane: PVC waterproofing membrane sheets are primarily used for waterproofing roof surfaces. This is essential in the implementation of a green roof or rooftop garden.

The main advantages of using PVC sheets include:

• • Mechanical strength (stability against environmental conditions)
  • Ease of shaping (high tensile strength and elongation)
  • Resistance to wear (high resistance to permeability)
  • Very high weldability (low flammability, self-extinguishing properties)

1. Protective Layer: It is essential to have a protective layer on top of the moisture barrier to protect the building’s insulation during the installation of the green roof, fertilization, and to prevent plant roots from penetrating the structure. The protective layer can be made from materials such as lightweight concrete, mosaic, thick plastic sheets, copper sheets, or a combination of these materials. Usually, affordable and readily available materials in each region are used.

2. Drainage Layer: This layer stores water from rainfall and irrigation, allowing it to drain and direct excess water to the building’s sewage system.

3. Growing Medium: This layer is where the plants are rooted. It can be made from lightweight soil, sand, or decorative stone chips. The choice depends on factors such as heat tolerance, direct sunlight exposure, and root growth.

4. Vegetation: The type of plants used on the green roof should be selected carefully based on factors such as heat resistance, direct sunlight exposure, and root growth.

In addition to these layers, proper waterproofing and drainage layers are crucial for the success of the project. Waterproofing of all vertical barriers on the roof and the boundaries on the sides should also be considered to prevent moisture leakage.

The use of geotextile layers, moisture drainage layers, and protective layers enhances the safety and efficiency of the insulation, drainage, and filtration system of the green roof.

Filter Layer: A filter layer is installed between the planting medium and the drainage layer. This filter layer helps to remove moisture from the roots of plants and prevents them from rotting or becoming dirty. Additionally, the filter layer acts as a separator between the soil and the drainage layer. Preventing the clogging of drainage with soil is one of the most important functions of the filter layer. Non-woven polypropylene geotextile with low gram weight can effectively perform this function.

Planting Medium: The planting medium refers to the layer where plants are grown. This space provides the necessary conditions for plant growth in a rooftop garden or green roof. Typically, the planting medium consists of fertilized soil. However, more complex types may include a mixture of mineral materials along with nutrients. It’s important to choose the type of soil based on the plant cover. The selected soil should have the ability to withstand erosion caused by irrigation or rainfall. Mixing soil with some sand and gravel can prevent it from washing away.

Plant Cover: The choice of plant cover is influenced by social, economic, and climatic factors. It’s essential to select a plant cover that suits the climate conditions. Climate conditions can vary seasonally, being very dry, very hot, very cold, or generally variable.

The resistance of the plant cover is critical, especially on extensive green roofs, as the prevailing conditions are often dry. It’s best to use drought-resistant plants on green roofs. Succulents and some species of Crassulaceae are examples of plants that can thrive in such conditions. Some succulent species are ideal for cultivation on green roofs. These plants come in various growth patterns and colors.

In this regard, sedum is the most common plant cover used on extensive green roofs. If sedum species are not suitable for cultivation, other succulent species can be used on extensive green roofs.