On November 7th, voters passed the Green Roof Initiative. This law requires ‘garden roofs’ to be installed on top of any new construction that is 25,000 square feet or greater below 50 feet. The law also requires any new roofing project on existing structures that are of similar size to include a garden roof. A commercial roofing project in must now take into account the requirements of this garden roofing mandate, and as such it is important to be aware of how this new law can affect your business.

Choosing a Garden Roof Type

First, it is important to understand what a ‘garden roof’ entails. According to the National Park Service, a garden roof is a layer of vegetation planted over a waterproofing system that is installed on top of a flat or slightly–sloped roof.


There are a variety of types of garden roofs. There is an ‘extensive garden roof’, which consists of a shallow growing medium (usually less than six inches) with less irrigation, limited plant diversity, and minimal watering requirements. The ‘intensive garden roof’ has a deeper growing medium, sometimes several feet in depth, with greater plant diversity and more heavy watering requirements. Intensive garden roofs can include things such as trees, and often come with more structural requirements as well as more intensive levels of maintenance. The ‘semi-intensive garden roof’ includes features of both the ‘extensive’ and ‘intensive’ variety, and can be more appropriate depending on your desired vegetation covering.


There are a few factors to consider when deciding which garden roof to go with. If money is the primary concern, the extensive garden roof is the more desirable option. A shallower growing medium means that there will be less materials required for the project. It will also cost less in terms of water usage, as well as labor required to keep the roof in a healthy state. Drought-tolerant and drought-resistant plants can be chosen to ensure that water is never a concern in regards to your roof-top garden. Extensive garden roofs are ideal for larger projects, and are a great option for those who are looking to comply with the law without having to hire a gardener or someone with extensive knowledge of plants.


An intensive rooftop garden may be something to consider if you want to make a statement and create an attractive environment on top of your business. Intensive garden roofs can be an impressive feature for a rooftop patio, one that lets your customers and clients understand you care deeply about your environmental impact. When considering an intensive garden roof, one must keep in mind the increased structural requirements, as well as the need for greater water usage. Intensive garden roofs will require a larger amount of maintenance and regular care, and are suited for those who are able to make a bigger commitment, both in terms of time and money.

Benefits of a garden Roof

Though this new initiative may seem like an economic burden, it is one that can be approached in manner that doesn’t create excessive financial stress upon your business. In fact, a garden roof done correctly can be great marketing material for your company, as it can highlight your business’s forward-thinking and innovative mindset. Depending on your desired design, a garden roof can be used to grow flowers that are then cut and displayed in your waiting room. Vegetables can be grown and served in company cafeterias, or donated to local food banks as a form of charitable giving and community outreach. garden roofs can be a source of inspiration for employees, as well as a way to enter an oasis on a lunch break. Studies indicate the presence of plants is a major mental health benefit, and a garden roof can increase this sense of well-being within your workforce.


The garden Roofing Ordinance requires structures that fall under the mandate to have a percentage of their roof covered with some type of vegetation, ranging from 20-60% of total roofing area of a structure. The goal of the initiative is to reduce urban heat islands, which create increased temperatures from the presence of radiating roofs and pavement. According to a 2014 study by Climate Central, ranked 3rd in the US in terms of its urban ‘heat island’ effect. By planting vegetation on roofs, the ‘heat island’ effect can be offset.


Garden roofing requirements can be offset by the presence of sustainable energy technologies, such as solar panels. A roof that falls under the new standard must be at least 30% garden roof of the total mandate amount. For instance, if a new roofing project is required to be at least 20% garden roofing, and the area of available roofing for the structure is 1,000 square feet, 200 square feet must have some form of vegetation or sustainable energy source. If a business wanted to implement as much sustainable energy as possible on this project, it would still be required to have at least 60 square feet of vegetation on the roof.


If your company is considering installing a new roof, it may be affected under the garden Roof Initiative’s new set of requirements. If your building’s structure is within the city limits, and is 25,000 square feet or greater, a new roofing project must include the same amount of garden roofing as new construction projects.

Rhino Roofing understands that this law has a tremendous impact on many future commercial roofing projects, and we want to work with your business to ensure that your roofing project complies with the new set of standards as defined by this law. We know that your business will want to comply with this law in the most economical way possible and we are more than happy to find the garden roofing solution that best fits your budget. We are confident that our vast understanding of diverse roofing projects will allow us to serve your company efficiently and effectively under the new era of garden roofing.