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What Is the Difference Between Extensive and Intensive Green Roofs?

February 21st, 2025

Green roofs have become an essential feature in modern architecture, offering a range of environmental, aesthetic, and economic benefits. Whether integrated into new builds or retrofitted onto existing structures, green roofs help to improve biodiversity, enhance insulation, and reduce urban heat. However, when planning a green roof installation, it’s crucial to understand the difference between extensive and intensive green roofs.

At Wallbarn, we specialise in high-quality green roofing solutions, including our innovative M-Tray® modular green roof system, which simplifies installation and maintenance for a wide range of buildings. In this blog, we’ll explore the key differences between extensive and intensive green roofs, their benefits, and how to choose the right system for your project.

What Is an Extensive Green Roof?

An extensive green roof is a lightweight, low-maintenance system designed primarily for environmental benefits rather than recreational use. These roofs typically feature shallow substrates and a selection of hardy, drought-resistant plants, such as sedum, moss, and low-growing wildflowers.

Key Characteristics of Extensive Green Roofs

✔ Lightweight – Generally, the substrate depth is between 60mm and 150mm, keeping the overall roof weight low.
✔ Low-Maintenance – Requires minimal upkeep, with occasional weeding and fertilisation.
✔ Drought-Resistant Planting – Typically features sedum, grasses, and small wildflowers that thrive in limited soil.
✔ Biodiversity Benefits – Encourages pollinators and improves local ecology.
✔ Excellent Water Retention – Reduces rainwater runoff and helps with stormwater management.
✔ Cost-Effective – Lower installation and maintenance costs compared to intensive systems.

Extensive green roofs are ideal for flat or slightly sloped rooftops and are commonly used on residential buildings, office blocks, and commercial properties where accessibility is not a priority.

Ideal Applications for Extensive Green Roofs

New-build residential projects
Commercial buildings and office blocks
Industrial warehouses and distribution centres
Small outbuildings, such as sheds and garages
Retrofitting projects where weight restrictions apply

Wallbarn’s M-Tray® modular green roof system is a perfect example of an extensive green roof, providing an instant, low-maintenance solution that is easy to install and long-lasting.

What Is an Intensive Green Roof?

An intensive green roof, often referred to as a roof garden, is a more complex system designed to support a wide variety of plants, including shrubs, perennials, and even trees. These roofs require a deeper soil substrate and more structural support due to their weight. Unlike extensive green roofs, intensive systems are fully accessible and can be used as recreational spaces.

Key Characteristics of Intensive Green Roofs

✔ Deeper Soil Depth – Typically 150mm to 1,000mm, allowing for a diverse range of planting.
✔ High Maintenance Requirements – Requires irrigation, fertilisation, and ongoing upkeep.
✔ Supports a Variety of Vegetation – Includes lawns, shrubs, flowers, and even small trees.
✔ Increased Weight Load – Heavier than extensive green roofs, requiring additional structural reinforcement.
✔ Creates Usable Outdoor Space – Designed for public access, recreational areas, and social spaces.
✔ Higher Cost – Due to increased structural requirements and ongoing maintenance needs.

Because of their higher weight and maintenance demands, intensive green roofs are often found on hotels, commercial developments, and urban residential projects where outdoor space is a key feature.

Ideal Applications for Intensive Green Roofs

Public buildings, hotels, and retail centres
High-end residential developments
Office buildings with recreational areas
Hospitals and healthcare facilities
Educational institutions and community spaces

Extensive vs Intensive Green Roofs: A Side-by-Side Comparison

Feature	Extensive Green Roof	Intensive Green Roof
Substrate Depth	60mm – 150mm	150mm – 1,000mm+
Weight Load	Lightweight	Heavy, requires additional structural support
Maintenance	Low, occasional weeding and fertilisation	High, requires irrigation and regular upkeep
Plant Selection	Sedum, grasses, moss, and wildflowers	Shrubs, perennials, trees, and lawns
Biodiversity	Supports pollinators and small wildlife	Can provide full-scale habitats for larger wildlife
Cost	Lower installation and maintenance costs	Higher cost due to soil depth and plant variety
Accessibility	Not designed for public access	Fully usable space for recreation and socialising
Stormwater Management	Good water retention and runoff reduction	Superior water absorption, reducing urban flooding
Lifespan	Long-lasting with minimal upkeep	Dependent on maintenance quality

Both types of green roofs offer significant benefits, but the right choice depends on the building’s structure, intended use, and maintenance capacity.

Why Choose Wallbarn’s M-Tray® for Extensive Green Roofs?

For those looking for a hassle-free and lightweight green roofing solution, Wallbarn’s M-Tray® modular green roof system is one of the best extensive green roof options available.

Key Benefits of M-Tray®:

✔ Pre-Grown Modules – Ready-to-install trays with established vegetation.
✔ Lightweight & Low-Maintenance – Perfect for retrofitting projects and new builds.
✔ Quick & Simple Installation – Modular trays slot together without the need for roll-out layers.
✔ Easy to Maintain – Individual trays can be removed for inspection without disturbing the whole roof.
✔ Sustainable & Biodiverse – Designed to enhance urban biodiversity and support local ecosystems.

M-Tray® provides an instant green roof solution, making it ideal for residential properties, commercial buildings, and industrial units where weight and maintenance constraints must be considered.

Choosing the Right Green Roof for Your Project

When deciding between an extensive or intensive green roof, it’s essential to consider:

Building load capacity – Can the roof support the additional weight?
Maintenance level – How much upkeep is required?
Biodiversity goals – Is the priority low-maintenance planting or a fully landscaped garden?
Budget constraints – How much is available for installation and ongoing care?
Accessibility requirements – Will the roof be used as a functional outdoor space?

For most residential and lightweight commercial projects, an extensive green roof like M-Tray® is the most practical choice. However, for urban developments, hotels, and community buildings, an intensive green roof may offer greater long-term benefits.

Find Out More About Green Roofs with Wallbarn

At Wallbarn, we specialise in high-quality green roof solutions designed for UK buildings. Whether you’re looking for a modular extensive green roof like M-Tray® or need advice on intensive green roof installations, our team is here to help.

📞 Contact us today to discuss your project and discover the best green roof system for your building.