Photo by Bilyana Dimitrova
Gardens can weigh quite a lot—soil is heavy and wet soil is even heavier. So when you’re doing any kind of significant roof design, you must bring in a structural engineer, says Julie.
In terms of design layout, if there are no taller buildings around yours, the garden will be exposed to 360 degrees of weather 365 days a year. You’ll need a hardscape and plants that can deal with a lot of sun, wind, and freeze/thaw conditions.
How will your family use your garden? The context (that is, your specific site conditions) combined with your preferences will dictate the core of your design.
Start with a high-quality waterproof membrane that’s well sealed. And yes, you need to buy a soil mix that’s specifically designed for a roof garden.
“Spiral staircases are often used to save space, but I’m not a fan,” says Julie. “I find them dizzying, inconvenient if you’re carrying things, and troublesome for little kids."
Most roof gardens should be watered twice a day, every day during the growing season. If you can’t do that, you need to install an automatic irrigation system.
You want lighting if you plan to use your garden at night. If you’re starting from scratch, you can make your lighting system a significant (and functional) design element.
Plants on roofs are highly susceptible to the impact of extreme (and rapidly changing) weather conditions.
Plants with some transparency are ideal for a roof garden—they give a sense of privacy without blocking the view.
Julie deliberately designed a low-maintenance roof garden for her family: “Someone from Four Gardens comes over for cleanups and replanting two or three times a year."