Green roof designs are becoming popular as a way of achieving a useful, environmentally friendly open space on an otherwise ‘lost’ flat roof. They can provide the following benefits:-

• Improving the local environment by providing wildlife habitats
• Improving sound and thermal insulation
• Reducing the amount and speed of rainwater runoff and forming part of a SUDS design
• Reducing the “heat island” effect in built up areas and helping to improve air quality
• Protection of the structure and waterproofing systems from UV, impact and abrasion, plant and bird infestation on the membrane
• Optimising the structural footprint by providing attractive natural areas in often high density developments, helping with the planning process and increasing values of properties

Wallbarn green roof systems are designed for extensive (low level) roof systems, some intensive (higher level) and bio-diverse (brown roof) gardens. It is essential that these areas are easy to access as they will require regular irrigation and maintenance.

Up to 50% of the rainwater can be retained in the vegetation and soil (depending on type of vegetation used and based on normal rainfall levels of up to 100mm pa) and the excess will run into the drainage system into the roof outlets at a slower rate, thereby putting less pressure on the drains.

The Protecto-drain boards hold approximately 5 litres of water per m2, and the filtration layer will prevent any particles passing through, ensuring the cups do not become blocked.

Because each component is supplied separately, access to and installation on roofs is easier than some other systems on the market. Also, due to its lightweight and flexibility, Wallbarn’s green roof system can be used for lining planters and vertical applications.

Bio-diverse roofs will have coarse substrates with lower nutrient levels and less absorption of rainwater. However, proper drainage and filtration systems still need to be installed.
Remember that landscaped podium decks have the same build up and maintenance requirements as a green roof – and offer the same potential benefits.

The System Build Up

The waterproofing membrane and insulation layer is installed, then the Wallbarn system comprises the following:-

• Wallbarn 3mm Protecto-board
• Geotextile filtration layer
• 20mm perforated Protecto-drain 20P
• Geotextile filtration and separation layer
• Growing medium (not supplied by Wallbarn)
• Pro-grass pre-seeded biotextile designed to aid the propagation of grass (to disintegrate over 3-4 months)
• Grass growth eventually covering the area (alternative vegetation can be planted)

It is advisable that lightweight, free-draining growing substrate material is used, and the roof deck is a maximum 15 ° slope.

Our system is designed for substrates up to 200mm deep. The substrate must be an absolute minimum 50mm deep and a maximum of 200mm deep. The weight of the green roof system will depend on the type of soil and vegetation chosen. Wallbarn systems will normally have a saturated weight of around 100kg per m2; but for certain soils and plants with a 200mm
substrate, the roof can have a weight of up to 250kg per m2.

IT IS ESSENTIAL TO ENSURE THAT THE ROOF STRUCTURE CAN WITHSTAND THE WEIGHT OF A SATURATED GREEN ROOF SYSTEM.

Wallbarn recommends that designers consider the factors such as roof strength and condition, access, the type of plants desired, environmental aspects and drain capacity before constructing green roofs.

Further technical details, installation instructions and alternative designs are available from Wallbarn. Please contact us to discuss your requirements in more detail.

Wallbarn provides A simple, lightweight, flexible drainage and filtration system suitable for accessed extensive and bio-diverse roof gardens