Extensive vs Intensive Green Roofs: What’s the Difference?

As sustainability and urban greening take centre stage in the UK construction and landscaping industries, green roofing has emerged as a smart, forward-thinking solution for both commercial and domestic developments. With its ability to deliver both visual charm and measurable environmental benefits, a green roof can enhance biodiversity, boost a building’s thermal performance, and manage excess rainwater effectively.

However, when it comes to choosing the right green roof system, one key distinction must be made: extensive versus intensive. These two types serve different purposes and require different structural and maintenance considerations.

This guide breaks down the differences between extensive and intensive green roofs, examining their construction, benefits, and suitability for various applications. If you’re planning a green roof and want tailored support, Wallbarn offers expert solutions and premium modular systems to meet your specific needs.

What Is a Green Roof?

A green roof – sometimes called a living roof – is a vegetation-covered roofing system built on top of a waterproofed roof structure. These systems typically include:

• A waterproof membrane

• A root barrier

• A drainage layer

• Filter fleece

• Growing medium (substrate)

• Vegetation layer

There are two primary categories of green roofs:

• Extensive green roofs

• Intensive green roofs

Each system comes with different performance characteristics and installation requirements.

What Is an Extensive Green Roof?

Extensive green roofs are lightweight, low-profile systems designed with minimal intervention in mind. With a substrate depth ranging between 60mm and 150mm, they are ideal for supporting hardy, drought-resistant plants such as sedum, mosses, and ornamental grasses.

These roofs are particularly well suited for buildings where weight load is a concern or where routine maintenance is not feasible. You’ll often find them on domestic properties, small commercial buildings, garages, or retrofitted flat roofs.

Features of Extensive Green Roofs:

• Lightweight – typically weighing between 60–150 kg/m² when fully saturated

• Low maintenance – requires minimal watering or gardening

• Biodiverse – supports insects and pollinators with wildflowers and sedum

• Shallow substrate – easier and quicker to install

• Economical – lower costs in terms of both materials and ongoing care

• Eco-friendly – helps reduce surface water run-off and provides insulation

At Wallbarn, our extensive systems are supplied in easy-to-install modular trays, pre-grown with established vegetation to simplify installation and reduce site disruption.

What Is an Intensive Green Roof?

In contrast, intensive green roofs are more akin to rooftop gardens. These systems can support a diverse range of planting, including shrubs, perennials, turf, and even small trees, thanks to substrate depths of 150mm to over a metre.

Due to their weight and the maintenance they require, intensive roofs are typically installed on purpose-built or reinforced structures. They are often used to create vibrant communal spaces, rooftop parks, or usable garden areas in residential blocks or commercial developments.

Features of Intensive Green Roofs:

• High load bearing – may weigh from 180 to 500+ kg/m² depending on depth and planting

• Versatile planting – can support lawns, flower beds, hedges, and trees

• Greater upkeep – involves regular watering, feeding, pruning, and weeding

• Structural demands – usually requires structural reinforcement or specific design planning

• Multifunctional – often designed as recreational or social spaces

Wallbarn’s intensive roof solutions are developed for longevity and resilience and can be adapted to suit even the most ambitious landscaping designs.

How to Choose Between an Extensive or Intensive Green Roof

Deciding between extensive and intensive green roofing depends on several practical and aesthetic factors:

1. Structural Capacity of the Building

Extensive systems place a lighter load on the building, making them suitable for retrofits and structures with limited load-bearing capacity. Intensive systems, being significantly heavier, are best suited for new builds or buildings designed with green roof integration in mind.

2. Intended Use of the Roof Space

If your goal is to boost thermal insulation and biodiversity without creating a usable outdoor area, extensive roofs are ideal. For a walkable garden or social space, an intensive roof offers the design scope needed.

3. Budget and Resources

Extensive roofs are more affordable to install and maintain. Intensive roofs require greater initial investment and ongoing care, but offer richer landscaping possibilities.

4. Maintenance Considerations

Those seeking a set-and-forget solution will benefit from the simplicity of extensive systems. If you’re happy to take on or outsource regular gardening, intensive roofs offer greater flexibility.

5. Environmental and Biodiversity Aims

Both options contribute positively to the environment. Extensive roofs offer efficient stormwater absorption and habitat creation. Intensive systems can be designed for food production, biodiversity corridors, or educational purposes.

Semi-Intensive Green Roofs: A Balanced Alternative

Some green roofs fall between the two categories. Known as semi-intensive systems, they offer a middle ground – typically involving a substrate depth of around 150–250mm. These roofs support a wider variety of plant life than extensive systems while remaining lighter and lower maintenance than full intensive designs.

This hybrid approach suits projects aiming to maximise biodiversity and planting variety without the structural or budgetary implications of a full garden roof. Wallbarn offers expert support in developing tailored semi-intensive solutions.

Sustainable Systems from Wallbarn

Whether you’re creating a simple sedum roof or a multi-functional garden above the city, Wallbarn delivers modular green roof systems that make sustainable landscaping achievable and efficient.

Our green roof range includes:

• Pre-grown tray systems for fast and clean installation

• Fully engineered substrate and drainage layers

• Design flexibility for both flat and pitched roofs

• Tailored support from initial concept through to completion

Each system is designed for performance, ease of use, and long-term sustainability. Our technical team is on hand to help you select the most appropriate option for your build.

Conclusion: Matching Vision to Function

Choosing between extensive and intensive green roofs isn’t simply a matter of cost or plant type – it’s about aligning the function of the roof space with the wider goals of the building. Whether you’re aiming to improve thermal efficiency, boost urban biodiversity, or create vibrant outdoor space, green roofs offer enormous potential.

With decades of hands-on expertise and a commitment to green innovation, Wallbarn is a trusted partner for green roof systems across the UK.

Explore our complete green roof range and discover how we can bring your rooftop to life – sustainably, beautifully, and professionally.