Intensive and Extensive Green Roofs: A Comprehensive Overview

Green roofs are becoming increasingly popular, and for good reason - they provide numerous benefits for the environment, buildings, and the people who inhabit them. Both intensive and extensive green roofs have their own unique characteristics.

Intensive green roofs are designed to support a wide range of plant species and can be quite heavy. They require a significant amount of soil and maintenance, and are often used in urban areas to create habitats for wildlife.

Extensive green roofs, on the other hand, are lightweight and require minimal maintenance. They are often used on large buildings or commercial properties where a cost-effective solution is needed.

The weight of intensive green roofs can be a concern, with some systems weighing as much as 100 pounds per square foot. This can put additional stress on the building's structure and foundation.

Green roofs come in two main types: extensive and intensive. Extensive green roofs have shallow growing media, typically between 4 and 6 inches deep, which allows for low-growing plants to thrive.

The expectation for extensive green roofs is that they will be low-growing and low-maintenance, but they still require regular stewardship to protect plants and maintain the environment. Plants on extensive green roofs usually top out at 16 inches tall, as any taller and the roots can't support the height.

Intensive green roofs, on the other hand, have deeper growing media, often up to 2 feet or more, which allows for taller plants, shrubs, and even trees to grow.

Intensive green roofs are the ultimate rooftop gardens, with depths ranging up to 2 feet or more.

Their extra depth allows for taller plants, shrubs, and even trees to thrive, making them perfect for creating a lush oasis in the sky.

You can expect to see a wide variety of plants on intensive green roofs, including herbs, grasses, and flowering plants.

Their water-holding capacity is significantly expanded compared to extensive roofs, making them a great choice for areas with limited rainfall.

Intensive green roofs are essentially rooftop gardens, lending perennial beauty to formerly bare roofs and decks.

Extensive roofs are a great option for those looking to add some greenery to their building without breaking the bank. They're designed to be low-maintenance and can store up to 80 percent of summer storm water, making them a great choice for areas prone to flooding.

Extensive green roofs typically use between 4 and 6 inches of growing media, with some professionals even growing plants in as little as 2 inches of media. This shallow depth means plants usually top out at 16 inches tall.

The expectation for extensive green roofs is that they will be low-growing and low-maintenance, but this doesn't mean they don't require regular care. A green roof does need regular stewardship to protect plants, add nutrition, and keep the environment balanced.

Extensive green roofs can be constructed with various layers of materials, including an insulating layer, waterproof membrane, drainage layer, filter fabric, gravel, another filter layer, substrate/growing medium, and plants. Not all layers are needed in every roof, so it's essential to liaise carefully with the architect.

There are three main types of extensive green roofs: Sedum Mat/Seed, which is the simplest and cheapest method of installing an existing or proposed roof. Sedum mats can even be rolled out like turf to instantly green an extensive green roof.

Extensive systems are simpler and lighter weight than intensive systems, ranging in thickness from 2-6 inches and weighing approximately 15-30lbs per sq ft. They require less structural support and can be used on roofs with a slope of 30° and higher.

Sedums are most commonly used in extensive systems because they're low maintenance and drought resistant, meaning they require minimal nutrients and irrigation. They're shallow, rooting self-generating plants that spread rapidly to quickly create a dense, vegetative cover with minimal soil.

A typical extensive green roof is made up of various layers of materials, including an insulating layer, a waterproof membrane, a drainage layer, a filter fabric, gravel, and another filter layer.

These layers work together to create a healthy environment for plants to grow. The insulating layer helps to regulate temperature, while the waterproof membrane prevents water from seeping into the building.

A drainage layer is crucial to prevent waterlogged soil, and a filter fabric helps to keep the substrate clean. Gravel is often used to improve drainage and prevent erosion.

The substrate or growing medium is the layer where plants actually grow, and it's typically between 4 and 6 inches deep. Some green roof professionals can even grow plants in as little as 2 inches of media.

Extensive green roofs typically use between 4 and 6 inches of growing media, and some professionals can even grow plants in as little as 2 inches of media.

Plants on extensive green roofs usually top out at 16 inches tall, due to the shallow growing media.

Extensive green roofs are designed to be low-growing and low-maintenance, but they still require regular stewardship to protect plants, add nutrition, and keep the environment balanced.

Low-maintenance doesn't mean no-maintenance, so be prepared to put in some work to keep your extensive green roof thriving.

The primary goals of extensive green roofs are environmental benefits, such as cooling and stormwater management, over creating human amenity space.

Increasing the planting depth by a foot or two can open up a whole new realm of possibility for your green roof.