The state of green roofs: past, present and future

Green roofs aren’t a modern invention. They’ve been used for centuries as a building technique. But, in the last few decades, they’ve reached new heights of popularity thanks to the environmental and structural benefits they deliver. 

At Permagard, we’ve supported hundreds of green roof projects by supplying systems and impartial advice for trade professionals and homeowners. We work hard to stay at the cutting edge of technology and developments within the industry, ensuring we offer the best service to our clients. That’s why we’re exploring the state of green roofs in 2025 and what lies ahead.

The state of green roofs

The green roof as we know it today, with individual drainage, storage and protection membranes, was developed in Germany in the 1960s. This lightweight, multi-layer system made them suitable for urban areas - unlocking their potential to green built-up areas.

Fast forward sixty years, and they’ve never been more popular. Around the world, more and more new buildings are being designed to incorporate them, utilising big and small spaces. The California Academy of Sciences covers acres and uses an estimated 1.7 million plants, while bus shelters in Bristol have been adapted to support tiny green roofs. Examples like these, along with their widespread adoption on domestic buildings, show that projects of every scale are being developed.

Given it’s where modern green roofs originated, it’s not surprising that Germany is leading the way in uptake. Stuttgart, specifically, is known as the green roof capital of Europe. The city has been actively promoting the inclusion of living roofs in new developments for almost forty years, resulting in more than 300,000 square metres of green roofs.

Part of the reason for an increased uptake globally has been financial incentives and tax breaks. Builders in Hamburg can benefit from a green roofing subsidy of up to 100,000 euros, while Stuttgart finances up to 50% of the installation up to a certain amount. Washington, DC, uses financial incentives for green roofs to combat issues with stormwater runoff, providing a rebate of $15 per square foot up to the cost of the roof.

In France, it’s a legal requirement for roofs on new commercial buildings of a certain size to be covered by green roofs or solar panels for at least 30% of the roof’s surface. For the 2024 Olympics, green roofs covered the athlete’s village in Saint-Denis. The inclusion of green roofs on buildings that were a focal point of the international community was no coincidence, it highlights the direction buildings will take in the future. 

There are also financial incentives available in the UK. Many councils offer grants for green infrastructure projects, and there are government grants for both residential and business properties. This has translated into some large projects, like New Providence Wharf, which has 3,000m2 of intensive green roofs. Although an accurate number isn’t tracked, by 2014, there were approximately 700 green roofs in central London, covering an area of around 175,000 m2. 

But it’s not just financial incentives that are making people decide to install green roofs. Thanks to a greater understanding and new technologies becoming available, it’s a practical choice for almost any building scenario.

Current green roof technology

Green roof technology has come a long way from its early iterations. A range of options is available that make green roofs viable on surfaces of any size.

Commercial green roofs

With the examples above of the enormous green roofs that are now installed, it’s clear green roofs are now a popular choice for new builds and professional installations, no matter their size. As their popularity has increased, materials and technologies have developed to make them more resilient and efficient, with features including:

High compressive strength

As walkable and driveable green roofs have become more popular and widespread in public spaces, the need for reliable membranes that can function under high compressive pressures has increased. 

Our PermaSEAL PRO 11 Geodrain has a high compressive strength of 500kN/m². It can withstand vehicle loads while continuing to provide effective drainage.

Fast drainage and water storage

As functional spaces, intensive green roofs need to remain usable even in poor weather conditions. Equally, rooftop gardens or podium decks may not be easy to irrigate and need to be able to withstand periods with no rain. Membranes now have the ability to store and drain large amounts of water to ensure spaces can withstand heavy rain and also dry periods. 

Our PermaSEAL PRO 60P Green Roof Drainage & Storage Membrane has 60mm deep cavities with a water storage capacity of around 20 l/m². Perforations allow water to move to the drainage space at the bottom of the membrane. This prevents too much water from being retained and damaging roots or saturating the growing medium. 

Bonded membranes

As walkable and drivable green roofs are subjected to a lot of pressure, many membranes now feature bonded filter or protection layers. This removes the need for multiple membranes but also prevents the layers from slipping and increases their compressive strength and drainage functions. 

Recycled materials

Green roofs are a green technology, and to enhance their sustainable credentials, many membranes are now made from recycled materials. At Permagard, we produce a range made with 100% recycled HDPE. By using recycled plastic, we save resources and reduce emissions. As HDPE can be used up to 10 times, these membranes can also be recycled again.

Domestic green roofs

There are more choices than ever for domestic green roofs. A variety of systems has made it a realistic option for the average home, allowing more people to take advantage of the environmental and aesthetic benefits. 

We’ve already seen products develop that make the installation process easier. Green roof kits contain all the essentials for establishing a green roof and just need the addition of a growing medium. Sedum trays are the latest development - they are self-contained trays that can be placed on top of a roof and come with established sedum plants.

Kits

Establish your green roof with high-quality components with our PermaSEAL Green Roof Starter Kit. This convenient kit contains a root barrier membrane, a drainage membrane and jointing tape. All you need to add is a growing medium and wildflower seed mix.

We also sell a range of separate components, ranging from membranes and protection fleece to wildflower seeds, edging pebbles, fertiliser and roofing trim so you can create a living roof of almost any dimensions or scope.

Trays

We’ve seen our PermaSEAL Sedum Trays grow in popularity among DIY and smaller commercial projects. They’re one of the quickest and easiest ways to establish a green roof. They just need to be placed on top of a Protection Fleece on a suitable primary waterproofing layer and clipped together, and the trays will act as a uniform green roof.

We predict these will continue to increase in popularity. Given the ease of installation and the modular nature that allows roofs of almost any size to be created with an instant, cohesive system.

Climate risk and sustainability

Green roofs are known for their environmental benefits. These include:

• Reducing pollution
• Providing a habitat for wildlife
• Retaining water
• Absorbing air pollution
• Reducing the urban heat island effect
• Dampening sounds

But is it all good news?

Although green roofs (in their modern form) have been around for decades, they are still relatively new compared to traditional roofs, and there are still questions about their functionality. Such as:

Fire safety

If a green roof is operating correctly and has enough water, it does not present a fire risk. As we’ve already discussed, membranes are now available with a storage capacity. So, even in the event of no irrigation, they can maintain themselves. However, should this fail or in the case of a poorly constructed roof without a suitable membrane, a green roof could dry out and be at risk of catching fire. Ultimately, the concern is that there hasn’t been enough testing to provide an accurate benchmark, but with the more recent introduction of the GRO Fire Risk Guidance Document, every effort is being made in the UK green roof industry to mitigate risks. It’s now recommended that all vertical elements of the green roof have a 500mm wide pebble or paving slab border around them. 

Ability to offset carbon

While their benefits aren’t in doubt, there are questions about whether their inclusion in large new buildings is tokenistic. If the average tree absorbs around 10kg of CO2 per year and building a skyscraper can produce hundreds or thousands of tonnes, the impact of a green roof will be minimal in offsetting this. However, this ignores the other benefits they provide.

Maintenance

Green roofs require maintenance. And that’s true whether it’s a small construction on top of a shed or a large-scale roof garden on top of an office building. This can involve irrigation, weeding out invasive plants or applying fertilisers. For large-scale living roofs, this can require a lot of work. Maintenance of the border fire breaks is also essential for the overall safety of the green roof. As a general rule of thumb, inspection twice a year is a good starting point. 

Beyond green roofs

As green roofs have developed, variations have emerged that perform specific functions or represent a key difference in construction. The two most popular varieties are blue roofs and brown roofs.

What is a blue roof?

The purpose of a blue roof is to hold rainwater so it can be released gradually. They do not necessarily have a green element and can just be formed of a waterproof membrane and a drainage layer. But adding a growing medium makes perfect sense, improving their functionality and delivering many of the benefits associated with a standard green roof.

How does a blue roof work?

A blue roof can use plants to capture and hold water, but the most important element is an outlet that restricts how much water can flow off the roof. This is set according to a flow rate that determines how quickly the roof can drain, preventing flooding. The addition of a living medium, like a green roof, can help improve their functionality and increase the benefits that they deliver.

If you’re interested in constructing a blue roof, get in touch to find out how we can support you.

What is a brown roof?

Brown roofs are very similar to green roofs in construction, but instead of being installed with a specific mix of plants, they’re allowed to self-seed with seeds that are windblown or carried by wildlife.

How does a brown roof work?

A brown roof has the same protective base as a green roof. A suitable membrane is laid, but then it’s left to develop in a way that mimics the natural space surrounding it. This can produce a more suitable habitat for local wildlife, as it more accurately reflects the spaces that they have adapted to.

What’s next for green roofs?

So, what does the future hold? The future is bright for green roofs. We’ll be seeing more and more, both in new constructions and retrofitted on existing buildings. With a projected 17% increase each year, it’s set to be a big industry with plenty of demand for those who can install effective green roofs.

We may see more legislation in the future that makes it a requirement to include green roof elements in new constructions. As of 2024, new developments and small sites need to deliver a 10% biodiversity net gain. One way to do this is to incorporate a green roof, but we may see them being explicitly required.

Green roofs themselves are likely to continue to evolve. We’re already seeing biosolar or PV green roofs becoming more popular. This dual technology incorporates solar panels and green roofs, delivering the benefits of both when installed properly. It’s a great way to maximise green technology in a single space. 

Other technologies and innovations are sure to emerge, as well as a reduction in costs for green roof materials as they continue to become more widespread.

Permagard: Green roof experts

Whether you’re a professional looking to install an intensive roof or a homeowner who wants to put a green roof on top of your shed, we have the expertise and products to make your project a success.

• PermaSEAL PRO 40P
  • Made from 100% recycled HDPE
  • Drainage and water storage capacity of approximately 15 l/m2
• PermaSEAL PRO 60P
  • Made from 100% recycled HDPE
  • Water storage capacity of approximately 20 l/m2 - making it suited to stormwater attenuation.
• PermaSEAL PRO 11 Geodrain
  • Dual drainage and protection membrane
  • Compressive strength of 500kN/m2
• PermaSEAL PRO 8
  • Has a high compressive strength and provides fast drainage.
  • Fully bonded with a high-quality geotextile filter fabric for easy installation
• PermaSEAL PRO 20P
  • Features an all-in-one drainage, storage and filter later with a fully-bonded, high-quality geotextile filter fabric to make installation quick and easy.
• PermaSEAL Sedum Roof Trays
  • ‘Instant’ green roof
  • Easy to install and maintain

For more information and to see our full range, visit our Professional Green Roof page. If you have any questions or would like more information, email [email protected] or call us on 0117 332 5824.