Designing and Installing an Intensive Vegetated Roof

Designing and installing an intensive vegetated roof requires careful consideration of several key factors. The first step is to ensure the roof can support the weight of the soil, plants, and any additional features such as irrigation systems.

A minimum depth of 4-6 inches of soil is necessary to support a wide range of plant species. This depth also allows for adequate drainage and prevents the soil from becoming waterlogged.

The roof's slope and drainage system must be designed to prevent water from accumulating and causing damage. A minimum slope of 2-3% is recommended to ensure water flows off the roof efficiently.

The choice of plants is also crucial, with native species being the most suitable for intensive vegetated roofs. These plants are adapted to local conditions and require minimal maintenance.

A different take: Intensive and Extensive Green Roofs

An intensive roof is a type of vegetated roof that's designed to thrive in rooftop landscapes with perennials, shrubs, and trees.

It's paired with a lightweight media blend to create a stunning rooftop park or terrace garden.

This system has a media depth of 8”- 48” and a saturated weight of 54 PSF+.

You'll need to contact Columbia Green for the system's weight, as it varies.

There are several types of vegetative roofs, each with its own unique characteristics. Intensive vegetative roofs are the most complex and diverse, with a deeper soil and growing medium that can sustain a wide range of plant life, including small trees.

Semi-intensive vegetative roofs offer a balance between intensive and extensive systems, with a thicker media depth that allows for a wider variety of plant materials and better biodiversity.

Extensive vegetative roofs, on the other hand, are simpler and less costly, but still offer many benefits such as stormwater retention and insulation.

Here's a brief comparison of the three types of vegetative roofs:

In terms of maintenance, intensive green roofs do require more upkeep than extensive systems, but the right plant selection and design can minimize this need.

An extensive roof is a type of vegetative roof that's perfect for buildings looking to save on energy and maintenance costs. It typically has a growing medium depth of six inches or less.

This shallow soil limits the diversity of vegetation, but it's a great trade-off because it reduces the weight load the roof must bear.

The Vancouver Convention Centre in Canada has a six-acre extensive vegetative roof, which is the largest in the country. It's home to 400,000 indigenous plants and four beehives of European Honeybees.

Extensive roofs are often inaccessible to the public, and they're usually installed solely for their energy- and cost-saving benefits.

One of the best things about extensive roofs is that they require significantly lower maintenance than intensive roofs.

Semi-intensive vegetative roofs offer a great balance between extensive and intensive roofs. They have a deeper substrate depth than extensive roofs, allowing for a greater variety of plants.

The Chicago City Hall building is a notable example of a semi-intensive vegetative roof, featuring a mix of 20,000 herbaceous plants, 112 shrubs, and two trees.

Semi-intensive roofs can be partially accessible, but they still require varying levels of maintenance. This is because they have a mix of areas with different substrate depths.

A semi-intensive green roof system has a thicker media depth, typically ranging from 6 to 8 inches, which supports a wider variety of plant materials. This includes grasses and perennials in addition to sedum.

This type of system is designed to be easy to install, with layers that can be cut to fit curves and irregular shapes.

Extensive vegetative roofs are a low-cost, low-maintenance solution that can be quickly installed and produce more immediate energy savings.

They often don't require extensive planning and can be retrofitted onto an existing building, making them a more accessible option.

Intensive vegetative roofs, on the other hand, are more expensive to install and maintain, and are best planned by an architect before a building is constructed.

This is because they require a lot of resources and have weight limits and size constraints that not all buildings can accommodate.

Extensive roofs provide a more immediate energy savings compared to intensive roofs, which typically offer more utility and greater plant diversity over time.

In contrast, extensive roofs are a good option for buildings that need a quick and easy solution for vegetative roofing.

Choosing the right plants for your intensive vegetative roof is crucial for its success. Intensive green roofs can sustain a diverse range of plant life, including small trees, perennials, grasses, shrubs, and even lawns.

The type of plants you choose will depend on factors such as the roof's slope, orientation, and climate. South-facing slopes receive more direct sunlight, requiring full-sun plants, while north-facing slopes are better suited for shade-loving plants.

For an intensive green roof, the plants should be durable and long-lasting if maintained correctly. It takes up to three years for the plants to fully establish and mature.

Some key considerations when selecting plants for your intensive green roof include:

By choosing the right plants and considering these factors, you can create a thriving and beautiful intensive vegetative roof that benefits both you and the environment.

Intensive vegetated roofs offer a range of benefits, from greater diversity of plant life to better insulation properties.

They can simulate natural areas and habitats found on the ground, making them more visually appealing than extensive vegetative roofs. This is due to their ability to sustain a much more diverse range of plant life, including small trees.

Intensive vegetated roofs can be used for a variety of purposes, such as recreation, growing food, public gathering space, and wildlife refuge. They can even be designed with the same biodiversity of a given location, restoring the entire environmental footprint of a structure.

However, intensive vegetated roofs require significantly more structural support, investment, maintenance, and irrigation compared to extensive systems. This is due to the increased weight and depth of the substrate and its vegetation.

To reduce weight loads, some planners use Geofoam, but this has negative effects on the environment, health, and stability. It's banned in many countries worldwide due to its hazards.

The maintenance of intensive green roofs without lawn is less than most people would expect, depending on plant selection and overall design. For instance, an urban rooftop forest hardly requires any maintenance other than professional trimming after every other year.

Here are some key benefits and considerations of intensive vegetated roofs:

Intensive green roofs can be designed to incorporate a wide range of plant species, including perennials, grasses, bulbs, summer flowers, shrubs, and large trees.

The installation process typically begins with a waterproof membrane, followed by a root barrier, insulation layer, protection layer, drainage layer, filter mat, growing media, and finally plants.

A well-engineered soil horizon is key to a successful intensive green roof, and can reduce water consumption by 50-80% compared to conventional systems.

Green Roof Technology's solutions often incorporate an artesian irrigation system, which operates accurately without electricity and is entirely invisible.

Here's a general overview of the installation process:

For an intensive green roof, the ideal slope range is 0:12-1:12 pitch, due to the greater weight of the roof and the deeper growing medium depth.

The steeper the slope of the roof, the more need there is for a reinforcing system and soil retention systems to prevent erosion and damage.

If your slope is south facing, it will receive more direct sunlight, requiring full-sun plants and possibly an irrigation system to ensure they thrive.

North-facing slopes, on the other hand, receive less sunlight, making them perfect for shade-loving plants.

Plants on the ridgeline will receive less water from rainfall than plants located on the eaves, so choose plants accordingly to ensure they get enough moisture.

When designing and installing a green roof, it's essential to follow a specific installation method to ensure its structural integrity and long-term success. The first step is to assess the structural capacity of the roof to support the weight of the green roof system.

The cost of the green roof system is a crucial factor to consider, as it will impact the overall budget and feasibility of the project. A well-designed and installed green roof can last for decades, but the initial cost can be substantial.

Worth a look: Roof Materials Cost

A waterproof membrane is the first layer installed on a green roof, providing a barrier against water and weathering elements. This layer is critical in preventing leaks and ensuring the roof remains dry.

A root barrier is installed below the waterproof membrane to prevent plant roots from growing into the roof's structural components. This layer helps maintain the roof's integrity and prevents costly repairs.

An insulation layer is an optional component of a green roof system, but it can provide significant energy savings and reduce heat transfer between the roof and the building. In colder climates, insulation is often a must-have.

The protection layer is installed on top of the insulation layer, providing an additional barrier against the elements and protecting the roof's components from damage. This layer can be made of various materials, including gravel or pavers.

The drainage layer is a critical component of a green roof system, responsible for removing excess water and preventing water accumulation. This layer is typically made of a porous material that allows water to pass through.

A filter mat is installed on top of the drainage layer, preventing debris and sediment from entering the drainage system. This layer helps maintain the roof's drainage efficiency and prevents clogs.

The growing media layer is the top layer of a green roof system, providing a substrate for plants to grow. This layer can be made of various materials, including soil, compost, or a combination of both.

Finally, plants are installed on top of the growing media layer, completing the green roof system. The type and variety of plants chosen will depend on the specific climate, soil conditions, and desired aesthetic.