Elevated Green Roof Systems
Green roofs have become increasingly popular in recent years, and in some locations have become mandatory, with rooftop plantings reducing energy costs, improving air quality, increasing biodiversity and reducing storm water runoff. One of the easiest methods of creating an instant green roof is to use plastic planter trays pre-filled with growing medium and plants
‘Extensive’ green roofs are typically defined as having growing media less than 8″ deep, use small, low-growing plant species such as succulents, require minimal maintenance and relatively low water needs.
A modular tray system filled with 4″-6” of growing media and plantings is generally the simplest and most versatile means of creating an ‘extensive’ green roof . But in many cases there’s a need to elevate the planter trays to cover service pipes, electrical conduits and surface irregularities, to raise the plantings to match the height of paved areas, or to correct for the slope on the rooftop.
For more information on green roof decks using planter trays, see our article on the Expert Insights page of GB&D magazine.
Fiberglass grating panels supported by adjustable height pedestals undoubtedly offer the most effective and versatile means of supporting raised planter trays. The fiberglass panels not only provide a solid base for the planter trays, but can provide support for pavers set among the plantings – porcelain, stone or concrete. Expanded polystyrene (EPS) foam is combustible and labor intensive to install while concrete pavers are extremely heavy and may exceed roof loadings with filled planter trays.
Some of the other benefits of using fiberglass grating panels to elevate and support an extensive green roof tray system include:
- less pedestals needed c.f. concrete pavers
- large panel size (typically 4′ x 8′) ensures much faster installation
- superior wind uplift protection – interconnected panels create a continuous surface
- allows space for irrigation pipes under the plantings
- water drains freely via the open grid structure
- minimizes weight loading – just 2.5 – 4 lb/sq.ft. (depending on panel thickness)
Archatrak Extensive Green Roof System
Archatrak has partnered with Columbia Green Technologies to supply a complete, elevated extensive green roof system – the patented interlocking and overlapping green planter trays are supported by a fiberglass grid laid over adjustable height pedestals, allowing porcelain, concrete or stone pavers to be easily incorporated in the overall design and set to any desired height relative to the planter trays.
Both planted-in-place and pre-grown options are available with the Columbia Green Technologies tray system. Pre-grown trays are pre-filled with media and established sedum plantings appropriately/ regionally sourced to ensure quick adaptation to the project climate zone. Planted trays arrive onsite palletized, are easily hoisted to the roof with a crane, ready to install and irrigate. If preferred, plant trays can be delivered empty with super sacks of growing media and with tiles or rolls of sedum (plantings) shipped separately, to be filled onsite.
Each function of a layered green roof system is incorporated in the trays, eliminating the need for separate drainage mats, water retention mats, root barriers, and filter fabric, but ensuring superior stormwater management and ease of installation.
- Stormwater management. Ridges and troughs at the base, capture and slowly release peak stormwater flows via a specific pattern of small drain orifices.
- Healthy, thriving plants. The ridge and trough design promotes the air flow necessary for plant growth and root health by preventing overly saturated media. The metered release of water allows plants ample time to uptake water and nutrients from the growing media without sitting in standing water.
- Interlocking edges. Tray edges overlap, linking the individual trays, which are further secured with pins to create a fully interlocking system. This tray design delaminates lateral wind pressures, thus reducing wind uplift across the entire installation. It also prevents trays from shifting apart, and allows trays to be overfilled with soil for invisible tray lines and a flexible soil depth.
- Environmentally friendly. The Columbia Green Tray is made from 88% post-industrial recycled polypropylene.
- Integrated high efficiency drip irrigation. Can be installed in planted-in-place systems.