Green roof on bitumen
From an existing bitumen roof to a green roof: we assess the options and provide a suitable substructure and professional installation.
Request a quoteCan a green roof be installed on bitumen?
Yes, a green roof can be installed over existing asphalt roofing, as long as the roofing is in good condition and the structure has sufficient load-bearing capacity. Root barriers and drainage must also be properly installed. We’ll assess what preparations are needed and determine which green roof is best suited for your roof.
What you can expect from us:
Assessment of Your Roof and Existing Roofing Material
Advice on root protection and appropriate roof construction
Clear quote for preparation and installation
How is a green roof installed on a bitumen surface?
The bitumen forms the waterproof base. On top of that is a green roof system that protects the roof covering, drains excess water, and allows the vegetation to grow. The installation consists of the following components:
Inspection of roofing, load-bearing capacity, and drainage
Install additional root barriers where necessary and apply a protective layer
Installing Drainage and a Filter Layer
Applying substrate as a growing medium
Planting sedum or other suitable plants
The exact construction depends on your roof and the system you choose. Sedum is therefore not laid directly on the asphalt. Any defects in the roofing must be repaired first.
How much does a green roof on bitumen cost?
The cost depends on the surface area, accessibility, and the type of green roof chosen. The condition of the bitumen also plays a role. Can the existing roofing remain in place, or are repairs and additional root protection needed first? In our quote, we clearly specify which services are included.
Check the cost of a green roof for an initial price estimate.
From a bitumen roof to a sedum roof
A sedum roof can be a suitable solution for a home, addition, garage, or shed with asphalt roofing. Suitability depends on the structure and roof construction. Even for a small roof, we therefore check whether it can support the additional weight, including stored rainwater.
Interested in seeing a completed project? On Cees Laseurlaan in The Hague, we converted an existing bitumen roof into a 360 m² sedum roof.
Does the bitumen need to be replaced first?
Not always. If the existing roofing is watertight, in good condition, and suitable for a green roof system, it may be possible to leave it in place. We also consider its expected remaining lifespan. It’s better to address a roof that’s due for replacement soon first.
In the event of leaks, damaged seams, or concerns about the roofing material, we’ll assess what work is needed. This helps prevent a new green roof from having to be removed later to repair the underlying layer.
Learn more about our approach to installing a green roof.
Choose your type of green roof
Sedum roof
Low maintenance and lightweight green roof for flat and gently sloped roofs.
View sedum roof
Sedum herb roof
Green roof with sedum and herbs for more biodiversity and variety.
View sedum herb roof
Native rooftop flower meadow
Biodiversity green roof with native flowers and herbs.
View native rooftop flower meadow
Green roof insulation (XPS)
Green roof with XPS insulation, ideal for energy savings and a pleasant indoor climate.
View insulation green roof
Inclined Green Roof
Green roof for pitched roofs up to 45°, specially designed for stable planting on sloping surfaces.
View sloped green roof
Retention roof (blue roof)
Green roof with water buffering to reduce peak sewer load.
View retention roof
Biobased green roof
Green roof with natural, biobased materials such as cork, jute and hemp.
View biobased green roofFrequently Asked Questions About Green Roofs on Bitumen
No. A suitable system must be installed between the bitumen roofing and the vegetation, including protection, drainage, and substrate. If the roofing is not root-resistant, additional root protection may be necessary. The exact layers depend on the system chosen.
No. There are special root-resistant bitumen roofing membranes, but not every existing bitumen layer has that property. We therefore check what type of roofing is in place and what protection is needed. Regular weed barrier fabric is not automatically suitable as root protection for a roof.
Yes, provided the roofing material, load-bearing capacity, and drainage are suitable. A small roof isn’t necessarily strong enough to support a green roof. It’s especially important to have the structure of a wooden shed or garage assessed in advance.
The weight varies depending on the system, layer thickness, and vegetation. In our assessment, we consider the water-saturated weight: the green roof including the water it retains. The chosen system must be compatible with the available load-bearing capacity. When necessary, this requires an assessment by a structural engineer.
That depends on the condition and expected remaining lifespan. Age alone isn’t enough. Seams, joints, and any damage must be assessed. Does the roofing need to be replaced, or is the roof leaking? If so, that must be addressed first. A green roof won’t fix a leak.
A sedum roof is low-maintenance, but not maintenance-free. This includes removing unwanted vegetation, checking the plants, and keeping drains clear. How often maintenance is needed depends on the system and the conditions. Read more about sedum roof maintenance.
