City life has many delights and exciting moments, but it also comes with the peril of disconnecting you from nature. When brick and concrete dominate the landscape and outdoor space becomes a premium feature, those who wish to build their own little garden need to start getting creative. This is how roof gardens came to be such a popular option for anyone wanting an escape from pavement and curbs.
Building a garden on the roof – where plants would not typically want to grow – is a very different situation than designing a veggie patch on a land surface, where many species thrive without much human attendance.
The challenge comes with figuring out logistics such as how to get the plants up there, if your garden will survive the environment, and whether they will grow too large for the space. There are also several practical considerations for a roof garden, the most essential of which is how much weight the roof can support, but we’ll get into that very soon.
From figuring out the size of your garden to the type of plants you should choose and how to properly landscape it, this guide explores all the important things there are to know when you plan on creating your own roof garden.
But first, let’s tackle one important question:
Why go through the trouble of building a roof garden?
Rooftop gardens are stunning, provide an amazing city sight, and offer a peaceful refuge in otherwise way too urbanized areas. But, aside from their aesthetic appeal, these gardens provide a slew of other major benefits. If you’ve been wondering whether it’s worth going through the hassle of building a roof garden, these arguments are sure to sway you in the right direction.
- A roof garden can improve air quality – Rooftop gardens filter polluted air not only through the photosynthesis of the plants but also through the soil. Green roofs also keep dust from spreading, resulting in a much cleaner environment.
- Building a roof garden is an effective way to use rainwater – Rain gives us free water and energy, and rooftop gardens are ideal for making the most of it since plants utilize rainwater right away. In fact, they are able to retain up to 80 per cent of it in the summer and up to 40 per cent in the winter. Plants atop rooftops not only collect rainfall but also function as natural filters for any water that flows off the building, moderating its temperature, flow, and impact on the building’s structure.
- Roof gardens can solve the Urban Heat Island effect – The Urban Heat Island effect – increased temperatures due to cars and heat coming out of concrete and pavement – is one of the biggest issues cities are dealing with. Rooftop gardens can aid with this issue through the plants’ evaporation process, which cools down the air around. Plus, if you decide to go for slightly taller plants, they will also provide shade for when you’re lounging in your garden,
- Roof gardens are energy efficient – Rooftop gardens can help with more efficient energy consumption by being excellent insulators – preserving heat in the winter and cool air in the summer. This means less need for AC in the summer and heating in the winter, which translates to less money spent on energy bills.
- Urban agriculture – Rooftop gardens open the door to urban agriculture – an ecologically responsible and popular initiative. This means converting your rooftop into a small farm that generates fresh food. It is true that you need to pick some plants that are resilient to wind, there are many ways to build a shelter so that even some more fragile plants can thrive.
- Roof gardens welcome wildlife – While the highlight of your rooftop garden will be the plants, don’t be surprised if you’ll also start to see a bit of fauna developing. Insects such as bees, butterflies or ladybugs, as well as birds, will start finding your rooftop oasis very welcoming.
- You can build a roof garden for your personal happiness – You’d be amazed at what a breezy summer morning atop of the city can do for your mental health and level of happiness. Being out in a green environment has proven very helpful for relieving anxiety and lowering stress levels simply because you breathe less polluted air and expose yourself to sunlight.
What are the main steps to building a roof garden?
Step #1 – Assess the rooftop and building
The first thing you need to do before you start planning your above-ground oasis is to figure out how much garden you can build. This means assessing the structural health of both the building and the rooftop. A few pots here and there won’t cause much trouble, but if you’re planning to set up a garden bed, keep in mind that even the shallow ones can weigh up to 60 kilos per square meter, so you need to ensure the roof can support that.
No matter how technical you consider yourself, having a qualified professional assess the structure is much safer than doing it yourself. Consult a structural engineer or an architect to help you out. They will also be more informed on whether you need to secure a building permit for the development you’re planning and can help you obtain one.
The strength, as well as the size of your roof, will help you determine whether you can build the structure and irrigation needed for a garden plot or if you need to think on a smaller scale, with potted plants that don’t put too much stress on the building’s structure.
Step #2 – Plan for safety and easy access
To fully enjoy your garden, you need to feel safe up there. First, make sure the entry area, as well as the stairs or ladder, are visible and easily accessible. In the eventuality of bad weather or any other hazard, you’ll want to be able to get down safely and rapidly. Make sure you measure the entrance, stairwell, and corridors to make sure everything you plan to bring up there fits.
The railing should be sturdy, and the height should be in accordance with local regulations. Umbrellas are a safety concern sometimes, but there are high wind-permeability-rated models available that have additional vents built into them, enabling the air to pass through without your shade breaker taking sail, as well as models with heavy bases that will keep the umbrella grounded.
To avoid hazards, make sure plants that sit too close to the ledges or hanging over are properly secured. This can seriously harm someone or cause trouble with the authorities.
Step #3 – Think out the design of your garden
After you’ve crossed the requirements for structural stability and building authorization and ensured safe access to the premises, the following step is to actually plan the design of your rooftop garden.
When creating the layout, you will need to consider a variety of aspects, just like in a regular garden. And while the aesthetic part is all up to you, make sure you don’t overlook any of the following if you want to also enjoy the garden’s functionality:
- Shade: If you have a rooftop garden that will be exposed to direct sunshine for most of the day, consider where you will place shade for those plants that require it as well as for yourself. Heat is emitted not only by the sun but also by the roof and surrounding structures, so keep that in mind when positioning your shade breaks.
- Wind: For roofs exposed to winds, you will have to include windbreaks in your design as well. Windbreaks that alter the flow of wind rather than totally halting it will be more effective, as solid windbreaks are more prone to be pushed over in stronger currents.
- Privacy: If you live in a densely populated region, you may want a bit of privacy, so think about methods to shade you from unwanted eyes as well. Well-placed trees and sun shades are the most convenient option, but you can also incorporate some screens or fences, which are great for vertical gardening as well.
- Electricity: Electricity isn’t necessarily required for a rooftop garden but having a weatherproof power outlet put anywhere on your roof may be beneficial for power tools and gardening equipment, as well as illumination if you intend to enjoy your rooftop garden under the stars. Solar-powered lights are also a great option if you want to go a more sustainable route.
- Drainage: Because some of the rain and plant water must go someplace, make sure you have proper drainage to allow the surplus to flow out. Ideally, the water should be directed into your gutters or, better yet, saved for reuse on your rooftop garden.
- Storage: Before you use up all the space that’s left with furniture and décor, make sure you factor in a storage area. Gardening requires some tools and equipment, including fertilizer, utensils, gloves, potting mix, buckets, and hoses, so add a place to store all these items. If you’re looking to optimize space, think of some ways to incorporate storage into your rooftop furniture.
Step #4 – Choose your plants carefully
Roof weather conditions are pretty varied. Some rooftops receive direct sunlight, while nearby structures. On some roofs, temperatures can go up to 170 degrees Fahrenheit, while others are exposed to strong winds. Considering the weather conditions on your roof while picking plants for your rooftop garden will help you make the right decision.
Here are some types of plants known to thrive in rooftop gardens:
Many rooftop gardens exposed to direct sunlight and wind require deep, frequent irrigation to thrive. If you don’t have the desire or skill to build a drip system or some other form of constant irrigation, you’ll quickly start to get tired of daily watering trips, carrying as much water as you can up to the rooftop. To avoid this, choose drought-resistant plants.
There are many beautiful and low-maintenance plants often used for xeriscaping that will make perfect roof garden plants such as succulents, cacti, and many other drought-resistant plants such as snow rose, sage, or butterfly weeds. Evergreen trees and shrubs are also a great option for a low-maintenance roof garden.
Don’t cross roof gardens off your list if you have a rooftop shaded by neighbouring structures. With the right choice of plants, you can have your dream garden even when sunlight is scarce. Go for plants that thrive in partial sunlight, such as primroses, Japanese forest grass, snowdrop, and foxglove.
If you are planning to try out urban agriculture, go for salad greens (lettuce, arugula or spinach), root veggies (carrots, potatoes, beets), or brassica veggies (broccoli, cabbage, cauliflower). You can also grow a shade-resistant herb garden with options such as chives, mint, parsley, and oregano.
In situations where there are no other buildings or trees to block the wind, many roof gardens face higher wind conditions compared to ground-level gardens. If that’s the case with your rooftop, choose low-growing plants and ground cover such as decorative grasses, hydrangeas, and honeysuckle bushes if your roof gets a lot of wind.
Flowering plants such as African daisies, coreopsis, Shasta daisies, nasturtiums, marigolds, portulacas, and zinnias are also quite wind-resistant. A lemon tree can also be a great addition to your garden, and so are the aforementioned veggies such as arugula, lettuce, garlic, radishes, and potatoes. Herb lovers can choose chives, thyme, sage or rosemary for a flavorful green patch.
Sun-thriving plants are a great choice for rooftops that receive at least six hours of direct sunshine daily. If you want to have a sunny and joyful rooftop garden, plant marigolds and wildflowers. If you prefer to harvest fresh veggies and fruits in your roof garden choose tomatoes and strawberries, and, if your rooftop can support it, a Japanese maple tree will thrive in full sun and will be the highlight of your oasis.
Rooftop gardens are a blessing in the middle of a harsh urban environment, and they are also a good opportunity to make more out of unused or neglected places. If you enjoy the prospect of being up high surrounded by plants while gazing at the stars, a roof garden is exactly what you need. As long as your roof is solid enough to sustain it, the sky is the only limit to what you can build.
So, take a good look up at the sky, arm yourself with a ladder and a tape measure, and take your gardening to new heights with a rooftop garden.
Do you already have a roof garden? Let us know what type of plants you enjoy growing on your roof and what your experience has been so far!