As advancements continue in the application of green roofs and expanding environmental applications to buildings and spaces, terms have also increased which can cause some confusion. Whether roof garden, sedum roof, green roof or other term, there are two key differences everyone needs to know – intensive green roof and extensive green roof.
When determining the type of green roof design there are three key identifiers:
An intensive green roof typically involves a thicker substrate layer, allowing for a wider variety of plant types, including trees and shrubs. Typically, these roofs will in excess of a metre or more in depth.
Due to the design and application of products, plants and potentially furniture, intensive roofs require more maintenance and structural support due to its weight. Such roofs are also the most common format for roof gardens and will cover smaller spaces.
In contrast, an extensive green roof has a thinner substrate layer and mainly consists of low-growing vegetation like sedum. It’s lighter, requires less maintenance, and is more suitable for extensive coverage on larger roofs.
Roof access can help provide a visual indication whether an intensive or extensive roof. As intensive roofs can be smaller but use greater depth such as roof gardens, access will be more visible and likely more decorative as you would any garden. Extensive green roofs which require much less maintenance may still feature some access in design particularly when covering large spaces but will be more functional in design while keeping majority of space allocated to sedum or wildflower coverage and drainage.
Extensive and intensive green roofs naturally lend themselves to certain plant types.
The shallow soil of an extensive green roof is suited to ground covers, grasses, sedum and succulents. However, the plant selection will depend on the intention of the green roof, too. When the purpose of the green roof is to sustain local biodiversity, grasses, wildflowers and even areas of gravel and bark (what’s known as a ‘brown roof’) create the perfect habitat for native birds and insects.
For more performance driven green roofs designed to insulate a building from the summer heat of summer and aid heat retention in the winter, lower-level cover of sedum carpet is more beneficial. Sedum species varieties from Sedum Supply are selected to be most effective in more shallow depth environments ensuring a higher tolerance to drought conditions.
The depth of substrate on intensive green roofs lends itself to a larger range of plant species. Most plant species can be grown on an intensive green roof given the right substrate depth but, just like any garden, it pays to be conscious of how big the plants you’re selecting will grow and what conditions they will tolerate.
The purpose of the green roof will play a big part in whether it’s designed to be intensive or extensive.
Sedum Supply are specialist in all green roof designs, extensive green roof design and suppliers of market leading materials to achieve effective, lasting green roof installations. Shop the full range online or speak to a member of our expert team to help plan your green roof project.
Share this article
