What Is the Difference Between An Extensive and An Intensive Green Roof?

As sustainability and urban greening continue to gain momentum across the UK construction and landscaping sectors, green roofing is becoming an increasingly popular solution for both commercial and residential projects. With the dual benefit of aesthetic appeal and environmental impact, green roofs are a powerful way to enhance biodiversity, improve thermal performance, and manage stormwater runoff.

At the heart of green roofing systems lies a critical distinction – extensive versus intensive green roofs. Understanding the differences between these two types is essential for architects, developers, contractors, and property owners looking to integrate living roofs into their designs.

In this guide, we’ll explore what defines each type, their construction requirements, benefits, and how to determine the right system for your project. If you’re looking for professional-grade solutions and expert advice, Wallbarn offers an exceptional range of green roof systems tailored for various applications.

What Is a Green Roof?

A green roof – also known as a living roof – involves the addition of vegetation layers over a waterproofed roof structure. These systems consist of several key layers including a waterproof membrane, root barrier, drainage layer, filter fleece, growing medium (substrate), and vegetation.

The two main types of green roof systems are:

• Extensive green roofs

• Intensive green roofs

Each serves a different purpose and is constructed with different performance expectations and design considerations in mind.

What Is an Extensive Green Roof?

Extensive green roofs are designed to be lightweight, low-maintenance, and relatively shallow in depth. Typically featuring a substrate layer of around 60mm to 150mm, these systems support low-growing, drought-resistant vegetation such as sedum, grasses, and mosses.

They are ideally suited for buildings where load-bearing capacity is limited or where minimal maintenance is preferred. Commonly seen on residential properties, garages, commercial buildings, and retrofitted roof spaces, extensive green roofs offer an effective and cost-efficient way to introduce greenery into urban environments.

Key Characteristics of Extensive Green Roofs:

• Lightweight construction – usually between 60-150 kg/m² when fully saturated

• Low maintenance – generally does not require irrigation or frequent upkeep

• Biodiverse planting – ideal for hardy species such as sedum and wildflowers

• Shallow substrate depth – allows for quicker installation and fewer structural modifications

• Cost-effective – lower initial installation and long-term maintenance costs

• Environmentally beneficial – improves insulation, reduces stormwater runoff, and supports local wildlife

Wallbarn’s green roof options include extensive systems that are pre-grown and supplied in modular trays, allowing for fast, efficient installation with minimal disruption.

What Is an Intensive Green Roof?

Intensive green roofs, on the other hand, resemble traditional gardens. With substrate depths of 150mm to over 1,000mm, they can accommodate a wide variety of plants, including shrubs, perennials, small trees, and even lawns.

These systems require greater structural support and regular maintenance, including irrigation, weeding, pruning, and fertilising. However, they offer immense design flexibility and can transform rooftops into functional outdoor spaces such as terraces, recreational gardens, or rooftop parks.

Key Characteristics of Intensive Green Roofs:

• Heavier load – often 180-500+ kg/m² depending on soil depth and planting

• Greater planting variety – supports diverse landscaping elements including trees, lawns, and flower beds

• High maintenance – needs consistent gardening and irrigation systems

• Increased structural demands – often requires reinforcement or specific design during construction phase

• Architectural integration – becomes part of the usable living or leisure space

Wallbarn’s advanced intensive green roof systems are engineered for robust, long-lasting performance and can be tailored to meet complex project specifications.

How to Choose Between Extensive and Intensive Green Roof Systems

The right choice between an extensive and intensive green roof depends on several factors:

1. Building Structure and Load Capacity

Extensive systems are lighter and better suited to buildings with limited structural strength or existing roofs requiring retrofit. Intensive systems, due to their weight and complexity, are typically installed on new builds or heavily reinforced structures.

2. Desired Aesthetic and Function

If your goal is to improve biodiversity or provide thermal insulation without regular maintenance, extensive green roofs are ideal. However, if you wish to create a rooftop space that people can walk on, entertain in, or cultivate, an intensive system will be the better fit.

3. Budget Constraints

Extensive systems are more economical to install and maintain. Intensive systems offer greater design flexibility and functionality but require a larger upfront investment and ongoing care.

4. Maintenance Commitment

If minimal maintenance is important to you or the end user, extensive green roofing is preferable. Intensive roofs require regular landscaping and upkeep, making them more suitable for managed or communal buildings.

5. Environmental Goals

Both systems contribute positively to the environment. Extensive roofs provide excellent ecological benefits with minimal inputs. Intensive roofs go a step further, offering a broader habitat range and even potential food production in the case of rooftop vegetable gardens.

Hybrid or Semi-Intensive Green Roofs

It’s worth noting that some projects incorporate semi-intensive green roofs, which combine characteristics of both extensive and intensive systems. These typically feature a substrate depth between 150mm and 250mm and can support a broader variety of plants while still maintaining a relatively low profile and load.

This hybrid approach offers a balance of visual interest, biodiversity, and reduced maintenance demands. Wallbarn’s expert team can help guide your decision based on bespoke project requirements.

Sustainable Green Roofing with Wallbarn

Whether you’re interested in a low-maintenance sedum system or a vibrant rooftop garden, Wallbarn provides premium, modular solutions for every green roof requirement.

We offer a comprehensive range of modular green roof systems designed to simplify installation, reduce long-term costs, and enhance sustainability outcomes for buildings across the UK.

Our systems are expertly engineered to ensure optimal drainage, root protection, and plant vitality. As a leader in green infrastructure, Wallbarn also provides technical support and tailored advice to ensure successful project delivery from start to finish.

Final Thoughts

The difference between extensive and intensive green roofs is more than just depth – it’s about the purpose, scale, and vision of your green space. Whether your focus is ecological enhancement, visual appeal, or functional outdoor living, understanding the characteristics of each system will help you make the right choice.

With decades of experience and a firm commitment to sustainable innovation, Wallbarn is your trusted partner for cutting-edge green roof solutions in the UK.

To explore our full range of high-performance systems, visit Wallbarn’s green roof page and discover how we can bring your rooftop to life.