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Design Roof Garden Case Study Analysis

Essay by   •  June 7, 2017  •  Case Study  •  2,199 Words (9 Pages)  •  1,636 Views

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Design, operation and development plan

1.        Introduction

Since starting a roof garden is a bit more complicated than planting on the ground, it will  take us step by step through the process, including how to set it up, what to grow, and how to maintain it. A green roof generally means a carpeting of plants on a roof, which improves the energy performance of buildings, using the space of the roof, reducing temperature in the building, reduces storm water runoff and etc. In many urban areas the residents have flowerpots or container gardens on their roofs; these aren't providing effectively the energy savings that green roofs do. The company is using green roof system.

1.1 Modular green roof system

The modular green roof system is a roof system where the plants are planted in portable containers or modules which together make up the green roof cover.

2.        Design

The company uses an architect to co-ordinate the project as well as the design and detailing of the building and roof, including material specifications. A landscape architect is also used for the layout of the planting areas and the selection of the plants. A mechanical engineer may be required to calculate the heating and cooling implications of the green roof, and to discuss integration with existing and proposed rooftop mechanical equipment and drainage needs. Depending on the primary function of the green roof, specialist consultants may also include a horticulturalist; a horticultural therapist; an ecologist or biologist; a roofing consultant; a planner; an artist; and marketing / advertising professionals. For designing the garden roof the company considered the following aspects in order to make the business successful:

2.1        Safety

It is important that strict safety considerations are taken into account during the planning and construction of the roof gardening, to protect against damage to property, human injury, or possible loss of life. The company wants the garden to be safe, therefore, the plan is to install fence and securely tie down all equipment since roofs are generally windy places and the company will further consult the local department of buildings for any necessary permits and regulations about fence height. It is a requirement of the National Building Regulations that the edge of a flat roof must be designed to prevent people from falling off. A fence should therefore be erected along the perimeter of the rooftop as a preventative measure.

2.2        Roof selection

The company will prefer to select the flat slap roof with the assistance of Kgoshi Mampuru correctional services and structural engineers due to easy access of the flat roof. The company inspected the membrane to determine if it needs to be repaired or replaced before the installation. Water and space will be the key limiting factors for many green roof habitats. The location of the roof will therefore influence both the design and selection of plants.

The table below lists elements which must be considered when identifying micro-climatic zones on a roof top:

Regional climate

The general climate of the region must be considered when choosing plants for a climate green roof habitat. For example, coastal versus inland.


Sloped roofs which face south or west experience less direct sunlight and are therefore cooler and wetter.

Sloped roofs which face north or east experience more direct sunlight and are therefore warmer and drier.


Plants in exposed areas of a rooftop experience higher wind influence. Wind stresses plants by increasing evaporation off their leaves, and damaging foliage and branches.


Some areas of the rooftop may be permanently or periodically shaded by surrounding buildings.

2.3        Access and exists

Access to the green roof site is crucial - not only for installation and ongoing maintenance, but also for bringing up materials, soil and plants.  The company design internal stairs or an extra elevator stop in the planning stages which is easy and relatively inexpensive. Where an elevator does not go to the roof, material will have to be transported by hand up stairs and utility ladders, or hauled up with a crane, both of which can result in additional labour and equipment costs. An interior ladder or staircase may be safer than one attached on the outside of the building, and access through a "man door" is preferable to a small roof hatch.

2.3        Weight

The very first step towards creating a green roof habitat is to determine whether or not your existing roof can accommodate the additional weight. A structural engineer will determine the carrying capacity of the roof prior to start of construction. As you know that wet soil is heavy, the company will need to figure out the sustainable weight load of the roof by consulting a structural engineer so that the company can be able to place their plants on the correct structure which cannot cause damage. The company will also take the weight of the compost into consideration. Carrying capacity of each roof will determine the quantity and the type of the plants to be planted.

2.4        Containers

To avoid risks like moisture and roots penetration, the container is best method to use than waterproofing because it serves double purposes. The container that the company intended to use is lightweight, but allows drainage. Although the green roof will retain much of the rain that falls on it, maintaining proper drainage on the roof is still very important. So that the plant roots don't burrow into your roof membrane, the company will lines the recycled-plastic trays with a fabric weed block. The following container’s depth can carry the weights that are displayed in the table:

Types of container depth (cm)

Weight capacity (kg)







The structural engineer will determine the carrying capacity of the roof per square meter in considering the strength of the roof slap.

2.5        Watering

Access to the roof gardening site is crucial - not only for installation and ongoing maintenance, but also for bringing up materials, soil and plants. During hottest months, the plants need to be watered daily. The method of watering the plants is to run a garden hose up the side of his building, and attaching it to drip lines and a timer system. The timer will be set on certain interval for 24 hours which will allows the Kgoshi Mampuru correctional services workers to go away for several days at a time without worrying about his plants dying.



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