Dos and Don’ts for a Green Roof Garden

Now that spring is officially here, many homeowners are enjoying the idea of outdoor projects for their homes, new or not. A popular trend nationwide is the roof garden concept atop residential homes – especially with the growing interest in eating organic fruits and vegetables these days. A green roof enables the growth of vegetation – be it plants, succulents, grass, herbs or vegetables. The best news is that a green roof can act as an extension of the natural surroundings and be part of a balanced micro ecosystem. 

The concept of roof gardens has been around awhile, and society has accumulated many different names depending on what region of the world you live in – from eco-roofs, to green roofs to garden or vegetated roofs, to living roofs. There are some substantial environmental benefits to having a green roof, along with the economical and aesthetic factors. It matters not what we call them, the reality is, it is important to know that one does not just toss some dirt on the roof of their home and expect it to work. A green roof may not even use soil but rather perlite or other and more porous materials.

Rumor has it that garden roof environments are new, as a result of the green movement, and that they can also be high maintenance and a risk. Images of water dripping through the ceiling of a living room come to mind. The reality is that roof gardens have been around for centuries, and much like everything else in the world, they just keep getting better. Technically the green roof profiles are now thinner and lighter than ever, and when built right, are safe.

According to the International Green Roof Association one social housing green roof project was erected around 1943 in a small town called Wohldorf-Ohlstedt in Norway for former concentration camp prisoners and the needy. Later when it became an upscale neighborhood, the green roof homes were in huge demand. In the United States one can see the green roofs of Rockefeller Center in New York City installed in the 1930s.

When it comes to a new home, your green roof must meet design load requirements. In fact, any roof needs to have a waterproofing membrane – including green roofs. Just make sure your builder knows early on about your plans for a green roof – and its purpose.  There’s a difference between growing plants or vegetation and a full on garden with irrigation systems in place. But overall there should not really be any issues for your new home to meet any structural requirements.

One of The Plan Collection homes that lends itself nicely to installing a green roof is House Plan # 116-1081. Caution is duly noted, however, when you’re retrofitted a green roof. The requirements will probably depend on the region of the country you live in and what loads your home was originally designed to sustain – be that rain, wind, snow, etc. They are designed with a waterproofing layer, drainage system and root barrier, plus the growing method for the soil and plants.A home's structure will need to be analyzed tto make sure it can accomodate the load of a potentially rain-soaked green roof, so climate drainage systems and plant choices are all part of the design process.

Also did you know you can get a green building certification (tax credit) with award points for the installation of a green roof?  Green roofs include these benefits: They reduce cooling and heating costs, assist with storm water runoff, help prevent flooding, are economical (vegetable gardens), and extend commercial space for an increase the property’s market value.

Here are a few of the variations on types of green roofs:

• Intensive Roof Gardens include much larger plants and water features like pools, waterfalls, streams, or ponds.
• The Extensive Green Roof Gardens. These are lighter and thinner and appear much like a standard flat or sloped roof. And is often planted with sedum which is ground cover, otherwise known as stonecrops.
• Semi-intensive Green Roof Gardens.  These rooftop gardens can house a variety of plants from flowers to herbs or native grasses.

When designing and building a green roof there are some things to be aware of, such as the fact that they all require irrigation in the beginning for the roots of the plants to take hold, and some green roofs do not require any water once they are established, depending on where you live. Succulents are popular because they are hearty and can live through tough weather conditions on a roof – even a drought. However drought-tolerant plants require a thicker growing medium which absorbs absorb large amounts of water in the case of rain.  Many people combine native grasses and some intensive roofs even have bushes and trees. The irrigation needs of a green roof are specific not only to the plants chosen, but to your local climate.  

When it comes to paying for a green roof, you may be pleased to know that the Environmental Protection Agency has already done your homework for you, estimating most green roofs cost between $10 to $25 per square foot, with variables.

Be sure to look at plans on The Plan Collection, the  ask your contractor if a green roof will work with your house plan.  

Lead image photo credit: Ricardo Gomez Angel on Unsplash