Rooftop gardens and urban farms: the future of sustainability using buildings

by Ofentse Sefolo
Rooftop gardens and urban farms: the future of sustainability using buildings

From architects and clients to water proofers and contractors, the topic of rooftop gardens is on many people’s minds. Over the past 15 years, we have seen the rise of rooftop gardens in commercial buildings and larger domestic dwellings.

Rooftop gardens are filled with shrubs, bushes, soil retention systems, various plants and furniture to create a new type of ultimate backyard that can be enjoyed by building occupants and guests. The motivation for rooftop gardens range from optimising space and reducing a project’s CO2 footprint to reducing energy consumption thanks to the garden’s ability absorb heat. A rooftop garden also retains heat within the building during winter months, which benefits the client in a number of ways.

The typical construction of a rooftop garden is a suspended concrete slab that can handle the weight loading of the garden. It is important to remember that a rooftop garden is very different to tiles or pavers because you have soil and plants that are very heavy. The concrete slabs need to be designed to handle the weight loading of not only the earth and plants, but also the water that is retained within the rooftop garden.

Apart from water tanks and swimming pools, rooftop gardens are one of the most challenging structures to waterproof with a membrane because of the high volume of water and water retention that creates stresses on the underlying membrane. Once the rooftop garden is sealed and filled, you will have drainage seals, blankets, plants, and earth. If leaks emerge after the installation, they will be very costly and time-consuming to fix because everything needs to be removed to reach the waterproofing membrane. The last thing anyone wants is to be called back on a project to fix mistakes, which is why it is essential to plan your rooftop garden correctly.

5 Tips on specifying a rooftop garden that won’t fail
1. Working with landscape architects and landscapers from the conception phase of the project is key. The plants that are chosen need to have roots that won’t damage the waterproofing system, so careful consideration needs to be given to the plants that are selected.
2. Specify a waterproofing system that can handle continuously damp environments because the membrane will always be in contact with water and without sunshine.
3. It needs to be system that has anti-fracture properties. A liquid membrane system, even if it has good crack-bridging properties, will not work. The stresses on the system will likely lead to hairline movement, so the system needs to be able to handle this type of movement.
4. Specify a membrane with high abrasion and root-resistant properties. Roots like to move into soft substances and this is where the membrane system can be compromised, which is why it is crucial to choose a system that offers good root-resistance.
5. The area is designed to drain water away, so the slab should be constructed with a fall, or allowances need to be made in the design to apply a screed waterproofing system to enable the drainage of water. Geotextiles, drain seals and smart designs can help you create a system that drains the water away.

What about urban farms?
With the global population set to exceed 10-billion people by 2050, the challenge of providing enough food for everyone in a sustainable and cost-efficient way is rising in significance. By shedding the restrictions of seasonal weather patterns, overcoming transportation challenges, and significantly enhancing yields, the growing trend of urban farming could herald the future of food production.

For thousands of years, human populations have farmed the land for food, but with the sharp rise in humans on our planet over the past few centuries, the pressure on traditional farming has continually increased. While modern techniques have enabled enhanced production rates, more than 11% of the earth’s total land area is now used for crop production, creating environmental challenges that range from soil degradation to habitat clearing. As our cities expand, the distances between farmland and the populations that consume its produce are growing, raising the impact of transportation.

A potential solution is the growing trend of urban farms, also known as vertical farms, a concept that sees the sprawling crop farms of old condensed into much smaller, factory-like sites where conditions can be optimised and yields can be significantly increased. Everything from the lighting and ambient temperature to the soil conditions and nutrients that the plants receive can be carefully controlled in urban farms.

Extensive vertical racking is used to optimise space in urban farms, enabling them to be established in a smaller urban site. Such a location reduces the food haulage that is needed to transport produce to consumers, cutting CO2 emissions. Geography aside, the creation of controlled conditions delivers many benefits. The process of crop production is insulated from seasonal weather patterns that are highly susceptible to disruption because of our changing climate.

Urban farms and rooftop gardens are only some of the smart ways that designers, scientists, produce manufacturers and developers are changing the way people live, consume and use their spaces. If you are working on ground-breaking sustainability projects, be sure to let FLOORS in Africa magazine know so that we can share them with our readers!

Specialised tip: Specify a waterproofing system for a rooftop garden that can handle continuously damp environments because the membrane will always be in contact with water and without sunshine.

Full thanks and acknowledgement are given to www.theb1m.com and www.gripset.com for some of the information contained in this article.

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