Green roofs, also known as eco-roofs or roof gardens, are gardens that are installed on top of buildings. There are two main types - extensive green roofs use sedum plants and only require 4 inches of soil, while intensive roofs can support a wider variety of plants and deeper soil. Green roofs provide multiple benefits such as reducing energy usage, absorbing stormwater, filtering air pollution, and creating wildlife habitats. They are made up of layers including a waterproof membrane, root barrier, drainage mat, and lightweight soil mix of aggregate and organic material to support plants. Green roofs are best installed on flat or low-sloped roofs but stabilization may be needed on steeper slopes.

1. Green Roofs
Roof gardens and Ecoroofs

2. Roof Garden
A roof garden is any garden that is located on
the roof of a building.

3. Roof Garden Types
• Various options exist for roof garden types,
such as a traditional garden setting, potted
plants, grasses, or sedum.

4. Ecoroof
• Instead of a traditional-looking garden, an
ecoroof uses sedum which only needs 4
inches of soil.
• There are hundreds of species of sedum,
which are hardy and water-storing plants.

5. Advantages of Green Roofs
• Reduction of energy usage (cooling & heating)
due to added insulation
• Lower storm water fees & storm water
absorption
• Air pollutant filtering
• Sound barrier in high-traffic areas
• Extends the life of a roof
• Can make a building look better
• Can help to restore wildlife habitats (birds and
butterflies)

6. Green Roof Components

7. Flat or Sloping Roof?
• Easiest to install and maintain on a flat roof.
• Can be installed on low-sloping roofs with a
rise of up to 3 ft for every 12 ft of length
without the need for stabilization.
• Steeper slopes may require a reinforcing
system such as a tray planting or terracing
system to hold soil in place.

8. Roof Condition
• It is important to check the condition of the
existing roof.
• Look for peeling, cracking, blistering, leaking,
or other signs of wear.
• Check the roof deck and other structural
materials for damage, wear, or rotting.

9. Green Roof Layers

10. Installation
Green roofs can be installed using a series of
planting trays or by creating an edged rooftop
landscape area.
With the decking (such as plywood) in place, here
are the steps to installing a landscape area on a flat
surface:
• Install a monolithic type waterproof membrane
(rubber or plastic) on top of the roof decking.
• Place a 6 mm sheet of plastic on the waterproof
membrane (this will serve as a root barrier).

11. Installation (continued)
• Top the first 2 layers with one or more thin sheets of ¾
in. foam insulation suited for use with damp soil.
(Insulation is only required when it is necessary to
increase the R-value for the roof over conditioned
spaces. If the space below the green roof is not
conditioned — over a garden pavilion or shed —
there’s no reason to provide anything more than some
protection for the waterproof membrane, such as thin
foam ‘fan board’ insulation or a layer of building felt.)
• Set a drainage mat (also called a dimple mat) with
capillary spaces on top of the insulation. To keep the
soil from clogging the mat, place the mat with the felt
side side up.

12. Installation (continued)
• Frame the sides for the roof with mesh gutter
guards, wood, or other edging that will permit
drainage to hold soil in place. Intermediate angle
supports may be needed to keep the vertical
edging sturdy. The horizontal leg of the supports
can be slipped under the drainage mat and
weighted with the topping soil to keep them from
overturning. It is best to make supports that don’t
penetrate the waterproof membrane surface to
prevent leaks.

13. Soil and Plants
• Add soil. The ideal depth for the soil layer (without
requiring special structural design) is 4-6 in.
• To make a lightweight soil mix: Blend an aggregate such
as expanded shale, slate or volcanic rock with an
organic potting soil. A blend of 85% aggregate to 15%
potting soil is good.
• When fully saturated with water, 4 inches of a blended
soil weighs about 27 pounds per sq ft.
• Set plants in place.
• Water to settle soil around plants.

14. Planting Trays or Mats
• If using trays, only the membrane and 6-mil plastic
sheet in the steps below are required. Be sure to create
a roof that will accommodate the width and length of
the trays without leaving gaps. The trays can be
planted with the same plants as a roof without
containers or purchased pre-grown commercially by a
nursery. With a tray system, edging is not necessary.
• Another option for green roofs is vegetated mats.
These are mats with succulents or other plants and are
grown on the ground in the same manner that some
nurseries grow sod.

15. Portland Ecoroof Guide
The City of Portland has a detailed online guide
on ecoroofs, including how to determine the
needs, design specifications, installation, and
maintenance.
http://www.portlandoregon.gov/bes/article/33
1490