Landscaping on Top of the House

Green Roofs

Thought of landscaping your roof? Now you can. You can have a roof garden or a greenroof. Both have been around for centuries, though modern technology has made the green roof a viable option where it was not before. A roof garden usually consists of container of plants of various sizes placed on top of a roof.

What is a greenroof?—essentially it is a vegetated roof system that is placed over a waterproof roofing
membrane on new construction or an existing building. The growing media and plants take the place of conventional roof coverings to protect the roof membrane. The number of layers and the layer placement vary, but at the very least all greenroofs include a single to multi-ply waterproofing layer, drainage, growing media and the plants, covering the entire landscaping deck surface of the roof.

Greenroofs generally fill into one of two categories: intensive or extensive--

An intensive or high profile greenroof requires a minimum of one foot of soil depth. These systems can support a wide variety of plants, from flowers to small trees, and can be used to achieve a landscaped surrounding. They look like traditional roof gardens because a much wider variety of plant material can be included since growing media depths are increased.

Architectural accents such as waterfalls, ponds, etc. are possible and these greenroofs provide recreation spaces and encourage interaction between people and nature. Of course, these roofs are relatively flat and depending on the plants used, the maintenance requirements can be high.

Extensive roofs – also referred to as eco-roofs, and low-profile – have thinner and fewer layers, so therefore they are lighter, less expensive and very low maintenance.

Extensive greenroofs are built when the key landscape desire is for an ecological roof cover with limited human access. The minimum growing media starts at about 2 1/2” to 6”. These greenroofs can be placed on slopes of up to 30 degrees, and steeper ones can be installed with raised grids to hold plants and growing media in place.

Greenroofs provide a myriad of benefits—

Provide new wildlife habitats

Lower the urban heat island effect by insulating and shading buildings and improving air quality.

Reduce the immediate water run-off greatly reducing flow rates. This also enables the outlets, downpipes, ground drains, sewer pipes, etc. to be reduced in capacity thereby lowering construction costs.

Alleviate pollutants through a garden roof's natural absorption and reuse of precipitation, eliminating overflow to the waterways, flooding streets and overflowing sewers

Provide sound insulation, reducing indoor noise pollution

Create aesthetically pleasing usable space that can generate more revenue for building owners

Convert normally unused roof areas for recreational use which saves the cost of purchasing additional land and can even aid in planning consent

Another large benefit is that garden roofs can save you – the building owner - money. Because of their insulating properties, garden roofs have been proven to reduce heating and cooling costs, and significantly slow a building's heat gain and loss. In addition, they protect roofing membranes against ultraviolet radiation, extreme temperature fluctuations and puncture or other physical damage, significantly increasing a building’s system's life expectancy.   So a green roof eventually pays for itself, while you enjoy.