A green roof, also known as a living roof, is a roof covered with vegetation planted over a waterproofing system. A green roof system can refer to a number of different systems, each with their own features and benefits.
As global urbanisation continues to strip our cities of green spaces, architects, contractors, and proprietors have a huge responsibility to find more sustainable, and renewable approaches to the design, construction, and operation of commercial buildings.
Sustainable infrastructure such as green roof systems are a popular solution. Green roof systems, also known as living roofs, are roof instalments that are often installed on commercial buildings and are either partially or completely covered with plant life and vegetation.
Green roof systems can have a variety of benefits such as reducing the overall impact buildings have on the environment, restoring eco-systems in our cities, improving health and well-being, and providing long-term structural support to buildings.
In this article, we will be looking into the four main types of green roof systems: extensive, intensive, semi-intensive, and brown (or biodiverse).
What are the four different types of green roof systems?
The Extensive green roof system
An extensive green roof is a green roof that is designed with a thin layer of soil, typically supporting drought-tolerant plants like sedums, mosses and grasses. They are lightweight and require minimal maintenance once installed. Their main goal is to provide visual or ecological benefits.
The biodiversity value differs according to the soil depth, but as they are often pre-planted with sedums (small, hardy succulents), moss, herbs and grasses, extensive living roofs tend to have lower biodiverse value. As they come with minimal maintenance and can be a DIY install, they are often used domestically. Key features include:
- Shallow substrate depth (2-6 inches)
- Typically pre-planted
- Modular or component
- Lower biodiverse value
- Zero to low maintenance
Extensive green roofs are particularly great for:
- Small residential projects such as sheds, garages and small extensions
- Retrofits and new builds
- Parks and gardens, where the focus is on creating a green space with minimal maintenance.
The Intensive green roof system
Differing from an extensive green roof, an intensive green roof, also known as a roof garden, is designed to support a wider variety of plants and features. It is the most 'involved' roof type which can be designed to be like a garden environment.An intensive green roof could include trees, shrubs and even water features.
Key features include:
- Roof garden.
- Deep substrate (1ft).
- Wide range of plants to choose from.
- Typically component build-up.
- Huge scope for design.
- Regular maintenance is required.
Small trees can be planted to add dimension and built structures such as seating or pergolas can be added to give this green roof system more usability.
Intensive green roofs are perfect for:
- Larger commercial projects, such as hotels, offices or shopping centres
- Recreational spaces, such as roof gardens or parks
The Semi-intensive green roof system
A semi-intensive green roof sits between the more extensive and intensive green roof types. It uses a thicker layer of growing medium than extensive roofs. This allows for a wider variety of plants, such as herbs, flowering plants, grasses and small shrubs.
This type of green roof requires a little more maintenance and occasional irrigation compared to other green roofs.
A semi-intensive green roof bridges the gap between extensive and intensive systems. It offers greater plant diversity, visual appeal and design flexibility while maintaining lower weight and maintenance than a full garden-style intensive roof. Key features include:
- Deeper substrate (4-8 inches).
- Typically component build-up.
- Ideal for designed roofs (aesthetics).
- Lower biodiverse value if for recreational use.
- Periodical maintenance.
Similar to intensive, semi-intensive green roofs are well-suited for:
- Visible, commercial buildings where it will enhance the overall aesthetic
- Spaces such as roof terraces and small gardens
- Buildings in busy areas to absorb noise pollution
The Brown/ biodiverse green roof system
Commonly known as 'brown roof', this type of living roof replicates biodiverse brownfield habitats with an intensive organic substrate. These are usually for the purpose of improving biodiversity or meeting environmental standards with a roof that is not overlooked, and your client requires minimal maintenance. Key features:
- Shallow soil layer of at least 2 inches.
- Pre-planted or left to naturally seed (colonisation).
- Log revetments.
- Recycled aggregates to provide additional micro-habitats.
- Modular or component.
- Zero to low maintenance.
A brown or biodiverse green roof is ideal for:
- Urban areas to help enhance biodiversity
- Rooftops, terraces and balconies to add visual interest and promote wildlife
- Commercial buildings to effectively seal and waterproof the space, while also enhancing the aesthetic
What plants are best for each type of green roof system?
As the soil depth and design ability differ between each roof system, plant and vegetation options are not one-size-fits-all. To ensure the vegetation takes to the green roof system and provides the best solution possible for your specific needs, it is important you select the appropriate plant life.
Plants for extensive, semi-intensive and biodiverse green roofs
- Armeria
- Thymus
- Oregano
- Sedum
- Saxifraga
Suitable plants for intensive green roofs
- Escallonia
- Carex
- Erigeron
- Alliums
- Lavender
- Rosmarinus
- Blechnum spicant
- Cosmos
- Verbena
To learn more about these plants and to help you select which plants to go for, you can find a detailed list in our blog titled “What are the best plants for green roof systems?”.
Green Roofs by Viritopia
As you can tell, we’re huge fans of green roof systems at Viritopia. From small-scale residential sheds to large commercial developments, our team has delivered green roofs that are as practical as they are beautiful.
Whether you are designing a residential green roof project, planning a community space or developing a commercial building that needs to meet green credentials, we are here to help bring your vision to life.
If you are curious about the benefits of green roof systems or would like to discuss your project requirements with an expert, contact us at Viritopia today.
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