What are Rooftop Gardens?

Rooftop Gardens

PHOTO: Jim Banks

Rooftop gardens are cultivated green spaces on the topmost levels of industrial, commercial, and residential structures. They may be designed to grow produce, provide play space, give shade and shelter, or simply be there as a living, green area.

Intensive green roofs are the heavy-weights, literally, of the green roof world. In essence, they are parks or gardens on roofs and are commonly known as Rooftop Gardens. The word ‘intensive’ actually refers to the amount of input required to maintain a green roof. As parks and gardens, they need frequent maintenance, just as a park or garden needs to be tended on a regular basis.

Rooftop Gardens capture a great deal of water and are therefore good Sustainable Urban Drainage Systems (SUDS) for stormwater management. They also provide a good thermal barrier and depending on the planting can also be good for biodiversity.

Fillmore Rooftop Garden

Rooftop Garden

PHOTO: Jim Banks

Example of Green Roof

Green Roof

PHOTO: Boston Magazine

Grass Living Roof

Grass Roof

PHOTO: Grass Roof Company

Rooftop Farming

Rooftop Farming

PHOTO: NPR

San Francisco's Better Roofs Mandate

San Francisco’s “Better Roofs” Mandate

Only a small percentage of San Francisco’s rooftops are put to productive use. With up to 30% of the City’s total land area composed of rooftops, there is a huge potential for using these empty spaces to generate economic, social, and environmental benefits. Living roofs are one of a number of sustainable design approaches that take advantage of underutilized rooftop space.

SF Better Roofs

Frequently Asked Questions

A rooftop garden can be any type of vegetation established on the roof of a building. Apart from aesthetics, rooftop gardens serve the purpose of providing architectural enhancement, temperature control, recreational opportunities, habitats for wildlife, and even a space for growing food. The method of cultivating food on the rooftop is referred to as rooftop farming.

They include conversion of CO2 emissions, production of oxygen, reduction of heat from buildings and energy costs, creation of habitats for wildlife, reduction of ambient temperature, capture and harvesting of rainwater, reduction of storm water runoff and discharge, as well as the creation of large catchment areas.

A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems. Container gardens on roofs, where plants are maintained in pots, are not generally considered to be true green roofs, although this is debated. Rooftop gardens, on the other hand, are known as an intensive green roof where more human activity is likely to be happening–along walkways and in communal areas. Rooftop ponds are another form of green roofs which are used to treat greywater. Vegetation, soil, drainage layer, roof barrier and irrigation system constitute green roof. —Green Roof, Wikipedia

Yes, though the building must first be checked by a structural engineer to determine the weight bearing capacity. Waterproofing must be in excellent condition, typically no older than 5 years, though having a green roof installed when you need to redo your roof is the best option. Having the waterproofing replaced right before the green roof is installed ensures maximum protection for the waterproofing and a more compatible system. This is also the best time to set up a leak detection system.

Intensive green roofs are commonly used on commercial buildings where owners desire large green areas that incorporate all sizes and types of plants. These roofs will have grasses, ground covers, flowers, shrubs and even trees. They will often include paths and walkways that travel between different architectural features to provide space where people can interact with the natural surroundings. Benches, tables, planter boxes, greenhouses, ponds and fountains offer people places to relax, dine or work in park-like settings.

Extensive roofs are more often used for single family and multi-family residential buildings. They are also best suited to spaces where people are seldom going to be walking on the roof surface. People walk on them mainly for maintenance. These green roofs also fit outbuildings like sheds and garages very well. Other names include “low profile” and “performance.” The design is supposed to give high performance to water use and thermal advantages, while keeping the overall weight of the roof low.

Extensive green roofs are the simplest to install and are very often added to existing roofs. Depending on the source you look at these roofs may add 10 to 35 pounds per square foot to a roof’s load.

A properly installed and maintained green roof should extend the life of the roof 2-3 times its normal life – 30 to 50 years is not an unusual lifespan for green roofs.

Counting all the material above the waterproofing, the cost of a green roof on a flat roof typically starts around $15 a square foot, with the average around $30 per square foot, and elaborate design and setups may cost as much as $200 per square foot or more. Inexpensive green roof pricing covers a basic 4” system with sedums and hearty herbs. Growing media depth, desired water storage, and plant material, and slope determine the increase in cost from there. Green roofs generally become up to 50% cheaper by the square foot as the square footage exceeds 10,000 feet.

The maintenance of rooftop gardens is perceived as a major hindrance to their installation. However, different types of rooftop gardens require differing levels of care, not to mention the savings accrued from a longer lifespan of green roofs. All commercial buildings with a rooftop garden will require roof and gutter checks at least twice a year, but otherwise maintenance may vary from weekly checks during summer in case of an intensive roof garden to quarterly or even twice yearly checks in case of the most extensive roof garden.

If you’re looking to create a container garden for your residential property, then yes, this is something you can learn to do for yourself. If you’re looking for a genuine rooftop garden that will provide maximum benefits to the environment and your property value, then you will need the assistance of a landscape design contractor with experience in rooftop gardens. This is true for commercial properties, as well. Adding a rooftop garden to a commercial structure is a complex process and requires the expertise of a trained professional landscape designer.

The two most specific qualifications for a qualified rooftop garden contractor are direct experience and depth of knowledge of sustainability practices. You need a landscape design contractor that has a deep understanding of what’s involved, what can potentially go wrong, and knows how to design a rooftop garden that will perform well and thrive for your property’s needs and specific conditions. Particularly when it comes to commercial properties, a strong depth of knowledge and expertise will save you time and money, making the investment in a rooftop garden a wise decision.

Korotkin Associates has extensive experience in horticulture, ensuring we have the knowledge to select the perfect plants that are well suited to a building’s light and climate conditions. We carefully select high quality, acclimated foliage, exotics and flowering plants from local nurseries. Our crews and project management team are specialists in drought-tolerant green infrastructure features and wildlife habitat landscaping, including the design, installation and maintenance of green roofs and rooftop gardens.

Learn more about the services we provide from this Case Study detailing the completed project and on-going management and maintenance services for the award-winning Fillmore Heritage Center Rooftop Garden.

Our rooftop garden has become a more attractive environment for the residents who have increased the use of the space. The recovery of the garden has contributed to the improved marketability of our real estate. —GARY COATES, Board President, Fillmore Heritage Center

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