Layered System

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Columbia Green offers layered green roofs in four configurations, specifically designed for extensive, semi-intensive, intensive and steeply sloped green roof applications. Each situation is unique, but some common reasons to choose a layered system include:

  • Extensive green roofs are the lightest option for retrofits or new construction with limited structural capacity. They start at about 19 lbs/ft² saturated weight.
  • Layered systems are the most compatible with curvilinear or organically shaped roof layouts because they can be easily trimmed to fit any geometry.
  • Layered systems offer maximum flexibility of soil depth. We recommend anywhere from 3-inches to 24-inches+ of media depth. All areas of the green roof need not have the same depth.




Growing Media

Retention Layer





3″ – 6″


FLL blended


3 oz.


Aluminum or Stainless Steel


6″ – 12″


FLL blended


3 oz.


Aluminum or Stainless Steel


12″ or Greater


FLL blended

.5-inch (opt.)

3 oz.


Aluminum or Stainless Steel


       Suitable for slopes up to 6:12. Available growing media depths: 3.5”, 4.5”, 6.5” or 8.5”


AutoCad Details / Guide Specifications / 3D Models/ Technical Information Sheets


System Components

  • Vegetation. Custom matched and most often regionally-sourced to meet each project’s design and installation parameters.  Choose from sedum cuttings, plugs, pre-grown sedum tiles (15”x20”) and pre-grown sedum mats (4’x 6’). Select accent plants may also be available.
  • Growing Media. Project specific, FLL approved, lightweight blends of inorganic and organic components are regionally sourced and available for delivery in bulk, small bag or super sacks/totes.
  • Retention Layer. Provides supplemental moisture retention for plant available water, high porosity for root aeration, and anchorage for plant roots. Composed of 100% recycled high tensile polyester fibers, this high-loft nonwoven geo-synthetic forms a UV stable, three dimensional blanket matrix for the growing media to lie on. Available in .5-inch or 1-inch thicknesses.
  • Filter Layer. The filter layer is adhered directly to the drainage layer for ease of installation. Fabricated from 50% recycled polyester, the non-directional weave design prevents gravitational erosion of the growing media.
  • Drainage Layer. Critical for preventing ponding and moving excess water across the roof surface to the nearest drain. Installed at the drainage plane, this unique layer of entangled polypropylene monofilaments, is load bearing and provides exception air flow to the growing media and thus to the root systems.  It is UV stable and crush resistant. Available in .40-inch, .75-inch, or 1.5-inch increments.
  • Edger. Maintains perimeter stability and delineates design and layout features. Available options:
    • Extruded Aluminum Edging (supplied by Permaloc®) is available in multiple heights including 4.5”, 6”, 8.5”, etc. Contact us for additional options.
    • Custom edgers provided by Columbia Green for sizes over 8-1/2” in height.


System Weight




• When should I use a built-up, aka layered system?

– Each situation and building is unique, but some of the common reasons to choose a built-in-place system include: when the structural capability of the structure is a limiting factor, organically shaped layouts, 5” or less of growing media is desired; OR for intensive roof gardens.

• What are the components and functions of the layered system?

– The layered system is comprised of the following components (moving up from the roof):

  1. Drainage Layer: critical for preventing ponding and moving excess water across the roof surface to the nearest drain.
  2. Filter Layer: To prevent soil fines from migrating downward onto the roof membrane.
  3. Water Retention Layer: Functions to supplement the water, nutrients and anchorage available in the lightweight, engineered soil.
  4.  Growing Media: lightweight media available in a variety of blends (all meeting FLL guidelines) to suit your specific project needs. Depths can range from 3” to 24” or more.
  5.  Plants: Layered systems can be planted with sedums, bulbs and other drought-tolerant plants hardy to your region. Sedums are available as cuttings, plugs or pregrown tiles.

• Which layered system should I use?

– This is project specific but the following general rules can be followed;

Extensive Layered System: For green roofs with depths ranging from 3″ – 6″.

Semi-Intensive Layered System: For green roofs with depths ranging from 6″ – 12″.

Intensive Layered System: For green roofs with depths of 12″ or greater.

• How is the Layered System installed?

– Please see the time-lapse installation video posted on the home page.

• What type of irrigation should I specify with the layered systems?

– We recommend standard overhead spray type system be used with our layered systems.  We have seen excellent results with the use of MP Rotator heads.

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