My Tips for Rooftop Garden Design

Making the most of all the growing space available in cities is key to a sustainable urban existence. Rooftop gardens are proliferating as people aim to grow their own food and flowers and to make city spaces greener.

While rooftop city gardens can be a wonderful idea, there are certain considerations and things to think about to make sure that such a scheme is a success. As a garden designer, I have worked to develop a range of rooftop gardens around the world. Here are my tips for designing a garden of this type.

Determine the Load-Bearing Capacity of the Roof

Many flat roofs can be used to develop a rooftop garden. But it is important to realize that not all flat roofs will automatically be suitable for this use.

If you have a flat area of roof where you would like to create a garden, one of the first things to determine is how much weight that roof can hold. Safety is key. It is vital to check the structural integrity of the roof.

Ideally, you should consult with a structural engineer who can tell you whether the roof is currently strong enough to support the weight of people, and of a garden. The roof in question may have to be reinforced before it can be used.

Consider Access and Practicalities

A rooftop garden can potentially become a haven and boon for people. But a garden of this kind will need to be safely accessible to be used. Think about how people will access the space, and also about how easy it will be to import the materials that will be required to make and maintain the garden.

One of the main challenges when it comes to rooftop gardens are the stairs that must be navigated to reach them. It can be challenging to get materials, tools, and other things you need to create and tend the garden up and down those stairs. So you may want to think about allocating space in the garden to keep these things on site (where space allows).

You might create a storage shed or storage area for tools, for example. And you should also consider a place for composting on the rooftop itself, so you don’t have to carry bulky, heavy organic materials up and down the stairs. And when you can create your own compost for a roof garden, this can save you money and avoid the need to import materials to fill pots and containers.

Water is another thing to think carefully about as you create your design. A garden which requires you to carry watering cans up flights of stairs will not be at all practical in the long-term. So you need to incorporate water in your plans from the outset. 

Think About Specific Environmental Characteristics

Before you even begin to think about what you will grow in a rooftop garden, how you will grow it, and what will go where, you need to analyze the site.

Rooftop gardens have a range of very specific characteristics. Often, key considerations for such a space can be wind-breaking and shade creation. Rooftops tend to be exposed and windy. They also have full sun exposure and can heat up and dry up quickly. Careful consideration of water and watering, the right growing method, and plant choices is key. The solutions and plants that you choose should be suited to these specific environmental conditions.

Determine How You Will Grow, Choose Growing Method(s)

When choosing a growing method, you should remember that rooftop gardeners use a range of different options. As in other garden types, you can grow in containers, either on the ground or in vertical systems, or in larger planters or raised beds. Often, rooftop gardeners consider growing hydroponically, in water rather than soil, or even consider aquaponics systems—rearing fish in addition to plants.

As you consider the different options, do be sure to keep weight in mind, and to consider how practical the option will be in your particular rooftop space. Only when you have looked closely at the space and chosen a growing method (or methods) can you zero in on the specific plants that you will grow.

Designing for People as Well as Plants

One final basic consideration for rooftop gardens is that you should design for the enjoyment of people, as well as creating optimal environmental conditions for the plants. City rooftop gardens are often not only exposed but also overlooked. Create privacy by blocking sight lines to give a rooftop garden a private and tranquil feel. Rooftop gardens can, however, also offer amazing views. So the enjoyment of particular vistas must be balanced with the desire for a more sheltered and private area. 

These are just some basic things to think about before honing in on the details when working on a rooftop garden design.