Flat Green Roofs

IMPORTANCE AND BENEFITS OF GREEN ROOFS

A green roof is a flat roof that is partially or fully covered with vegetation and soil. It is an innovative and environmentally friendly solution that provides numerous benefits both for building owners and for the environment.

Benefits of green roofs:

• Improved thermal performance – cooling the building in summer and providing insulation in winter, reducing overall energy consumption
• Rainwater retention – slowing down runoff into the sewer system and helping prevent sewer overload
• Improved air quality – filtering dust and harmful substances and producing oxygen
• Increased biodiversity – creating space for plants and small animals

ACCESSORIES FOR FLAT AND GREEN ROOFS

In addition to waterproofing and other basic flat roof components, accessories play an important role in ensuring the functionality and appearance of flat and green roofs. Properly selected and installed roof outlets, gedge dividers, and other accessories ensure reliable rainwater drainage, roof protection, and an aesthetically pleasing finish.

Roof Outlets

A roof outlet is a key component of flat roofs, designed to drain rainwater from the roof into the sewer system. A properly functioning roof outlet prevents water accumulation on the roof, which could otherwise lead to water ingress into the building interior, damage to the roof structure, and other issues. The roof outlet must be installed at the lowest point of the roof to ensure optimal drainage. According to ČSN 73 1901, at least two roof outlets must be installed per roof area, or the drainage capacity of the outlets must be taken into account. Each roof outlet type has a defined effective drainage area in square metres. If only one roof outlet is designed for a roof area, it must be supplemented with an emergency overflow in accordance with the manufacturer’s recommendations.

An important aspect of roof outlet use is regular inspection, which should be carried out at least twice a year (as specified by ČSN 73 1901). This is necessary to clean debris from the roof outlets and prevent clogging or damage (for example, ice damage during winter). Regular inspections and maintenance also extend the service life of flat roofs. Early detection and repair of issues can prevent more serious and costly repairs later on.

Visit our product page for roof outlets and extensions, where you will find individual product types and detailed technical specifications.

Inspection Chambers for Green Roofs

In green roof systems, inspection chambers play a key role in ensuring reliable drainage of rainwater from the vegetation layer while also facilitating maintenance of the entire system. While the roof outlet performs the primary function of collecting and draining water, the inspection chamber adds several important benefits. The first is protection of the roof outlet against damage and clogging caused by root growth and intrusion of organic material. The second is easy access for inspection and cleaning of the roof outlet within the extensive green roof layer. Inspection chambers must be designed to allow rainwater to freely reach the roof outlet. This means the chamber must not be wrapped in geotextile. Instead, it must be surrounded by a gravel layer that allows water to flow to the roof outlet.

We manufacture inspection chambers for green roofs from tough polyamide PA6 in sizes 300 × 300 mm, 400 × 400 mm, and 550 × 550 mm. The size is selected primarily according to the height of the green roof layer; for thicker layers (over 500 mm), we recommend using the largest possible chamber size. The chambers can be built up to the required height of the green roof layer using TWZN extensions with heights of 50 mm and 100 mm, matching the chamber dimensions. To ensure sufficient space for roof outlet maintenance, we recommend a maximum chamber height of approximately 1,500 mm.

The cover of the protective inspection chamber is made of polypropylene and is available either as a solid cover (TWZ) or a perforated cover (TWZF). When a solid cover is used, sunlight does not enter the chamber, which can be advantageous for green roofs as it helps prevent algae growth in drainage systems. The load-bearing capacity of the chambers with both cover types (TWZ, TWZF) is 300 kg, corresponding to load class K3. The chambers are therefore walkable, but not trafficable.

Another option for protecting roof outlets in green roofs—especially roofs with gravel layers—are aluminium protective chambers, available with or without a perforated cover. These are manufactured in sizes 250 × 250 mm and 300 × 300 mm, with heights of 100 mm or 200 mm. All chamber variants are made of 1.5 mm thick aluminium with 8 mm perforations. We therefore recommend surrounding them with gravel with a fraction of 8 mm or larger.

The same approach can be used to protect through-wall outlets and emergency overflows located in green roofs or roofs with gravel layers. These are made from the same material—1.5 mm thick aluminium—and are available in heights of 100 mm or 200 mm, with an optional perforated cover. The difference lies in their dimensions (150 × 250 mm) and the fact that one side is open, creating an opening positioned at the outlet of the through-wall outlet or emergency overflow, allowing free water flow. Aluminium chambers for these applications are neither walkable nor trafficable.

Explore our complete range of inspection chambers for green roofs and choose the solution perfectly suited to your project.

Edge Dividers

On green roofs, edge dividers are used to separate vegetation layers from gravel zones or to terminate the roof edge where no parapet is present. The basic types of edge dividers include aluminium, stainless steel, or plastic-coated variants, available in a wide range of heights. Newer designs also include corner and curved edge dividers.

We manufacture edge dividers from plastic-coated sheet metal or 1.5 mm thick aluminium, with a standard length of 2,000 mm. On flat roofs, edge dividers can be anchored to the waterproofing layer using cut strips of waterproofing membrane. Grey plastic-coated edge dividers already have these membrane strips integrated. For aluminium edge dividers, holes spaced at 250 mm intervals are prepared for threading waterproofing membrane strips through. The aluminium version is more versatile, as it can be installed on roofs with various waterproofing systems (mPVC, TPO/FPO, bituminous membranes, EPDM, etc.), with membrane strips prepared according to the roof covering. The rigidity of the edge divider is ensured by a 10 mm bend at the ends of both arms. Each product includes a connecting piece for easy continuation of the divider. Both divider variants are made from plastic-coated sheet metal or aluminium with 8 mm perforations, and we therefore recommend surrounding them with gravel with a fraction of 8 mm or larger.

More information about individual edge divider variants can be found in the Other Roof Elements section.