&A
Portland’s Ecoroof
Program is a cooperative
effort of the Bureau of
Environmental Services
and the Office 
of Sustainable
Development. The 
program promotes 
ecoroofs by researching
ecoroof technologies
and providing 
information and 
technical assistance to
community members. 
Qu e s t i o n s n s w e r s
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C I T Y  O F  P O R T L A N D  E C O R O O F  P R O G R A M  -  Q U E S T I O N S  &  A N S W E R S
Ecoroof opportunities come in all sizes: 
Large commercial buildings, residential homes and garages, or as small as a toolshed or kiosk.
An ecoroof is a lightweight, low-maintenance vegetated roofsystem used in place of a conventional roof. The City ofPortland is encouraging the use of ecoroofs as part of its
efforts to promote sustainable development. This means using 
practices that respect natural systems and limit impacts on the 
environment. Sustainable development practices promote 
environmental, economic, and social health today, while also 
protecting and sustaining the well-being of future generations. 
WHAT IS AN ECOROOF?
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C I T Y  O F  P O R T L A N D  E C O R O O F  P R O G R A M  -  Q U E S T I O N S  &  A N S W E R S
Ecoroofs are 
a proven 
technology 
and have 
been used 
in Europe 
for over 40
years. They 
are now 
gaining 
recognition 
in the US
for the 
environmental,
economic, 
and social 
benefits they
provide.
q What are the benefits of Ecoroofs ? 
Based on documented experience and studies, an
ecoroof offers several important benefits not found
in conventional roofing:
• Captures and evaporates from 10 to100 percent
of the precipitation that falls on it. This reduces
the volume and speed of stormwater runoff
leaving the site, helping prevent sewer over-
flows and protect receiving rivers and streams.
• Lowers the temperature of stormwater runoff,
which helps maintain the cool stream tempera-
tures needed by fish.
• Improves outdoor air quality by decreasing air
temperatures and reducing smog.
• Increases vegetation and wildlife habitat on
urban sites that typically have neither. 
• Provides insulation and lowers cooling costs for
the building.  
• Provides an attractive alternative to 
a conventional roof.
• Lasts twice as long as a conventional
roof, saving replacement costs 
and materials
• Creates a market for recycled materials,
such as compost, mulch, soil and other
ecoroof components.   
• Creates jobs in multiple industries.
• Is an approved stormwater management
technique under Portland’s Stormwater
Management Manual requirements for
new development and redevelopment. 
• Can earn floor area bonuses for pro-
posed buildings in Portland’s Central City
Plan District. Increasing the building
space that would otherwise be allowed. 
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C I T Y  O F  P O R T L A N D  E C O R O O F  P R O G R A M  -  Q U E S T I O N S  &  A N S W E R S
r Where can an Ecoroof be used ? 
• Ecoroofs can be located on flat or pitched roof
structures at a slope up to 40 percent (or 5 in 12
pitch).  They can be used on most types of com-
mercial, multifamily, and industrial structures,
as well as single-family homes and garages. 
• Ecoroofs can be used for new construction or to
re-roof an existing building.
s What does an Ecoroof cost ?
It is important to note that there is a wide range of
costs, depending on many factors.  Installation of an
ecoroof costs from $10 to $25 per square foot (sf).
This includes materials, labor, and structural
upgrades.  A conventional roof installation ranges
from $3 to $20 per sf.  As the ecoroof market devel-
ops, costs may decrease.
Although ecoroofs initially cost more than conven-
tional roofs, they are competitive on a life-cycle basis
because of reduced maintenance and replacement
costs (see question #5). 
Ecoroof
(cost per square foot)
$10 to $15
$15 to $25
Conventional Roof
(cost per square foot)
$3 to $9
$5 to $20
New construction (including
structural support)
Re-roofing
Source: Bureau of Environmental Services estimates based on City of Portland
demonstration projects, and information obtained from roof contractors.
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t What Are the Components of an Ecoroof ? 
Ecoroof configurations vary, but typically include the elements shown in the diagram and described on pages 4-8.
A - Structural roof support
B - Waterproof membrane
C - Root barrier (if needed)
D - Drainage H - Drain
Parapet
(edge of
building)
Flashing
E - Growth medium (soil)
     2-6 inches
Mulch or materials
   to prevent wind
   and rain erosion
G - Gravel Ballast (optional)
            Separation structure
               (optional)
F - Vegetation
     (succulents, such as sedum;
     herbs; grasses
ECOROOF diagram 
(figure 1)  section view - not to scale
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C I T Y  O F  P O R T L A N D  E C O R O O F  P R O G R A M  -  Q U E S T I O N S  &  A N S W E R S
A - STRUCTURAL ROOF SUPPORT
For Re-Roofing
The structural roof support must be sufficient to hold
the additional weight of the ecoroof. Check with an
architect, structural engineer, or roof consultant to
determine the condition of the existing building 
structure and what might be needed to support an
ecoroof. This might include additional decking, roof
trusses, joists, columns, and/or foundations.
Generally, the building structure must be adequate to
hold an additional 10 to 25 pounds per square foot
(psf) saturated weight, depending on the vegetation
and growth medium that will be used.  (This is in
addition to snow load requirements.)  An existing rock
ballast roof may be structurally sufficient to hold a 
10-12 psf ecoroof.  (Ballast typically weighs 10-12 psf.) 
For New Construction
The project architects and structural engineers can
address the structural requirements of an ecoroof dur-
ing the design process.  Greater flexibility and options
are available for new buildings than for re-roofing.
The procedures for the remaining components 
(B through I) are the same for both re-roofing and
new construction. 
B - WATERPROOF MEMBRANE  
(IMPERMEABLE LINER) 
Waterproof membranes are made of various materi-
als, such as modified asphalts (bitumens), synthetic
rubber (EPDM), hypolan (CPSE), and reinforced PVC.
Some of the materials come in sheets or rolls and
some are in liquid form.  They have different
strengths and functional characteristics.  Many of
these products require root inhibitors (refer to C) and
other materials to protect the membrane.  Numerous
companies manufacture waterproofing materials
appropriate for ecoroofs. 
C - ROOT BARRIER (IF NEEDED) 
Root barriers are made of dense materials that inhibit
root penetration.
The need for a root barrier depends on the water-
proof membrane selected.  Modified asphalts usually
require a root barrier, while synthetic rubber (EPDM)
and reinforced PVC generally do not. Check with the
manufacturer to determine if a root barrier is
required for a particular product. 
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C I T Y  O F  P O R T L A N D  E C O R O O F  P R O G R A M  -  Q U E S T I O N S  &  A N S W E R S
D - DRAINAGE LAYER (IF NEEDED)
There are numerous ways to provide drainage.
Products range from manufactured perforated plas-
tic sheets to a thin layer of gravel.  Some ecoroof
designs do not require any drainage layer other
than the growth medium itself, depending on roof
slope and size (for example, pitched roofs and small
flat roofs).  
E - GROWTH MEDIUM (SOIL)
The growth medium is generally 2 to 6 inches thick
and well drained. It weighs from 10 to 25 pounds
per square foot when saturated. A simple mix of
1/3 topsoil, 1/3 compost, and 1/3 perlite may be suf-
ficient for many applications.  Some companies
have their own growth medium specifications.
Other components could include: 
•  Digested fiber
•  Expanded clay or shale
•  Pumice
•  Coir 
Ecoroofs are an evolving industry, with new mate-
rials and approaches continually being developed.
In Europe, for example, recycled clay roof tile is
being used as a growing medium and a modular
design has recently been developed by a US firm.
These soils are
prone to wind
erosion when
exposed. It 
is important 
to ensure 
good plant 
coverage 
and/or mulch.
spring blooms
late summer color
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C I T Y  O F  P O R T L A N D  E C O R O O F  P R O G R A M  -  Q U E S T I O N S  &  A N S W E R S
F - VEGETATION 
Ecoroof vegetation should have the 
following attributes:
• Drought-tolerant, requiring little or no 
irrigation after establishment 
• A growth pattern that allows the plant to 
thoroughly cover the soil 
• Self-sustaining, without the need for fertilizers,
pesticides, or herbicides
• Able to withstand heat, cold, and high winds 
• Very low-maintenance, needing little or no
mowing or trimming 
• Perennial or self-sowing
• Fire resistant 
A mix of sedum/succulent plant communities is 
recommended because they possess many of these
attributes. Herbs, forbs, grasses, and other low
groundcovers can also be used to provide addition-
al benefits and aesthetics; however, these plants
may need more watering and maintenance to 
survive and keep their appearance. 
Installation
Four methods (or combinations of
them) are generally used to install the
vegetation: vegetation mats, plugs/pot-
ted plants, sprigs, and seeds.  
1 Vegetation mats are sod-like, 
pre-germinated mats that achieve immediate full
plant coverage.  They provide immediate erosion
control, do not need mulch, and  minimize weed
intrusion.  They also need minimal maintenance
during the establishment period and little ongo-
ing watering and weeding.
2 Plugs or potted plants may provide more design
flexibility than mats. However, they take longer
to achieve full coverage, are more prone to 
erosion, need more watering during establish-
ment, require mulching and more weeding.
3 Sprigs are hand broadcast. They require 
more weeding, erosion control, and watering
than mats.  
4 Seeds can be either hand broadcast or
hydraseeded. Like sprigs, they require 
more weeding, erosion control, and watering
than mats.  
New modular
units with soil
and vegetation
have been 
developed and
are now 
available.  
For plugs, sprigs, and seeds, it is extremely important to protect 
the growth medium from erosion (e.g., using mulch, netting, or gravel)
until it is fully covered by vegetation. 
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C I T Y  O F  P O R T L A N D  E C O R O O F  P R O G R A M  -  Q U E S T I O N S  &  A N S W E R S
G - GRAVEL BALLAST (IF NEEDED) 
Gravel ballast is sometimes placed along the
perimeter of the roof and at air vents or other
vertical elements. The need for ballast depends
on operational and structural design issues.  It is
sometimes used to provide maintenance access,
especially to vertical elements requiring periodic
maintenance.  In many cases, very little, if any,
ballast is needed.  
• In some situations, a header or separation
board may be placed between the gravel bal-
last and adjacent elements (such as soil or
drains).  
• If a root barrier (C) is used, it must extend under
the gravel ballast and growth medium, and up
the side of the vertical elements.
H - DRAIN 
As with a conventional roof, an ecoroof must safely
drain runoff from the roof.  It may be desirable to
drain the runoff to a rainwater harvesting system
such as (rainbarrels or cisterns), or other stormwa-
ter facilities such as planters and swales. 
I - IRRIGATION
Irrigation is likely to be needed during the estab-
lishment period and possibly during drought condi-
tions, regardless of the planting method used.  This
can be accomplished either through hand watering,
a manually operated low-tech irrigation system
(such as spray heads or soaker hoses), or an auto-
mated irrigation system. To minimize water needs,
early autumn is the best planting season. The goal
is to minimize the need for irrigation by paying
close attention to plant selection, soil and various
roof characteristics.
Spraying seed mix for new ecoroof
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C I T Y  O F  P O R T L A N D  E C O R O O F  P R O G R A M  -  Q U E S T I O N S  &  A N S W E R S
u What Are the Operations, Maintenance,
and Replacement Needs? 
Similar to conventional roofs, ecoroofs require some
degree of care to maintain optimum function.
VEGETATION/GROWTH MEDIUM 
Periodic inspection (at least twice a year) is needed 
for any type of roof to ensure drain inlets are not
blocked.  For ecoroofs it is also important to check 
the health and coverage of the vegetation; some
replacement or filling may periodically be needed.
Depending on the design, some plants may “brown
out” or almost disappear from sight; however, they
are still viable and will revive in the rainy season.
Depending on the planting method, weeding and
mulching may be needed during the establishment
period and periodically thereafter over the life 
of the ecoroof.
FIRE SAFETY
Sedum and other succulents are naturally fire 
resistant, almost eliminating fire concerns. Other types
of vegetation could be of concern and need 
to be watered, mowed, and/or maintained to prevent
fire. Depending on the seasonal rains in Portland, it is
best to mow a dry grass roof before July 4th. 
ACCESS 
Most buildings require roof access for operations and
maintenance. Access is needed for mechanical units,
window washing, elevator repair and other activities.
These should be identified during the design phase,
and access paths of gravel or other inert
materials provided. In cases where access
is needed only occasionally, paths may
not be required because the vegetation can tolerate
some foot traffic.
LEAKAGE
An ecoroof is considered less likely to leak than a
conventional roof.  If a leak does occur, it has been
speculated that it may be more difficult to pin point
the leak on an ecoroof than a traditional roof.
However, because ecoroofs are thin, they can be
removed and replaced in mats or sections.
REPLACEMENT
According to various sources the typical lifespan for
an ecoroof is about 40 years, significantly longer
than a conventional roof. This is because the mem-
branes are of good quality and the plants and
growth medium protect the membrane 
from weathering. Replacing an ecoroof involves:
• Removing and stockpiling the vegetation, growth
medium, irrigation pipes, and drainage layers. (It
may be possible to simply move these materials to
one side, rather than removing them entirely.)
• Removing and replacing the waterproof membrane.
• Reinstalling the stockpiled growth medium, 
vegetation, and other components.
The typical
lifespan
for an 
ecoroof is
about 
40 years.
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C I T Y  O F  P O R T L A N D  E C O R O O F  P R O G R A M  -  Q U E S T I O N S  &  A N S W E R S
v Where Can You See Examples 
of Ecoroofs?
The City of Portland has helped install ecoroofs
as demonstration projects including one at the
Environmental Services treatment plant.
Property:
• Hamilton West Apartments Building
(SW 12th and Clay)
• Buckman Terrace Apartments 
(NE 16th and Sandy)
• Jean Vollum Natural Capital Center
(NW 10th and Flanders)
• Whitaker Pond Shelter 
(NE 47th and Columbia Slough) 
• Columbia Boulevard Treatment Plant
• Multnomah County Building
501 SE Hawthorne Blvd
• B&O Building
SE Washington Street and 2nd Avenue
• Hawthorne Hostle
3031 SE Hawthorne Blvd
• People’s Food Co-op
3039 SE 21st Avenue
To arrange a tour, contact:
Ecoroof Program (Environmental Services) 
503-823-7267 or 503-823-7740
Ecoroof Program (Environmental Services) 
503-823-7267 or 503-823-7740
Ecotrust: 503-227-6225
Education (Environmental Services)
503-823-7185
Main Desk: 503-823-2400
Open to public 8:30 am - 5:00 pm  Check with 
security on the main floor.
Pat Lamb - 503-233-6600
Viewable from sidewalk
Viewable from sidewalk
C I T Y  O F  P O R T L A N D  E C O R O O F  P R O G R A M  -  Q U E S T I O N S  &  A N S W E R S
w What Permits Are Needed?
For Re-Roofing
• A building may need upgraded structural support
for an ecoroof, although many existing buildings
are structurally sound enough. In either case, a
signed document from a structural engineer is
required in order to receive a building permit
from Portland’s Office of Planning and
Development Review (OPDR). 
• An ecoroof may require alteration of downspouts
or other piping, requiring a plumbing permit
from OPDR.
For New Construction 
• For new development and redevelopment proj-
ects, an ecoroof permit is obtained through the
standard application process.  
• The ecoroof and other stormwater management
elements must be reviewed by the Bureau of
Environmental Services to verify the ecoroof is
constructed to meet the City’s Stormwater
Management Manual requirements or for Floor
Area Bonus approval.
x Where Can You Get More
Information and Assistance?
• Ecoroof Program (Bureau of Environmental
Services): 503-823-7267 or 503-823-7740
• Stormwater design techniques (Bureau of
Environmental Services): call 503-823-7740 or
http://www.cleanrivers-pdx.org
• Green building approaches (Office of
Sustainable Development): call 503-823-7222 or
http://www.sustainableportland.org
• Building code and permitting information
(Office of Planning and Development Review):
http://www.opdr.ci.portland.or.us or call 
503-823-7310 (for building code information) or
503-823-PLAN (for zoning information)
DESIGN AND INSTALLATION ASSISTANCE
Some vendors, design consultants, and installation
contractors known to the City at the time of this
printing are listed here.  These providers offer a
variety of services.  Some may be limited to provid-
ing information about their specific products (such
as impermeable liners), while others may be able
to manage the entire project, including design,
specifications, arranging for installation, and plant
procurement. The list is for informational purposes
only and does not
constitute a rec-
ommendation by
the Bureau of
Environmental
Services or 
City of Portland.
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CONTACTS
This is a list of contacts, which have spoken of experience or demonstrated it to the Bureau of
Environmental Services (BES). Experience which is in regard to design, construction or another type
of direct experience with ecoroofs. This list is for informational purposes only and does not consti-
tute a recommendation by BES or the City of Portland.  If you would like to be on this list please
submit your contact information and specific information about your involvement with ecoroofs.
VENDORS
MANUFACTURER REPS
American Hydrotech Inc. 
Seattle: 206-441-6125
Illinois: 800-877-6125
www.hydrotechusa.com
Bain Associates Inc.
Portland: 503-452-0788
Jbherman@aol.com
Garland Company Inc.
Portland: 800-762-8225 ext. 655
Mobile: 503-860-4420
Seattle: 800-762-8225 ext. 515
www.garlandco.com
Green Grid
Chicago, Il: 312-424-3319
Greengridroofs.com  
Green Tech
888-323-4397
W.P. Hickman
503-231-0280
206-841-7663
Sarnafil SA
Mass: 800-451-2505 ext. 257 
www.sarnafilus.com/GreenRoofs.htm 
Soprema Inc.
503-524-3382
800-356-3521
www.sopremaworld.com
Tremco Incorporated
Portland OR: 503-234-6407
Ohio: 800-321-7906
www.tremcosealants.com
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C I T Y  O F  P O R T L A N D  E C O R O O F  P R O G R A M  -  Q U E S T I O N S  &  A N S W E R S
CONTRACTORS
Anderson Roofing Co., Inc.
503-294-0202, Doug Christie
anderson.roofing@comcast.net
All About Roofs
503-538-5066
Green Seasons Turf and Tree Inc.
503-263-4567
Northwest Raingardens
877-887-1149
Oregon Landscape Contractors
Association
503-253-9091
www.oregonlandscape.org
Teufel Landscape
503-646-1111
CONSULTANTS
AEI
Portland: 503-452-8003
www.alpha-eng.com
Greenroof Design Consultant
770-674-4624
www.Greenroofs.com 
Green Roofing Consultant
Quebec, CAN 418-682-2478
Ma_boivin@videotron.ca
Greenworks
Portland: 503-222-5612
Mf@greenworkspc.com
HOK Architects
Washington D.C: 202-339-8728
www.thehokplanninggroup.com 
Katrin Scholz-Barth Consulting
Washington D.C.: 202-544-8453
Katrin@Scolz-Barth.com
Lango Hanson
Portland: 503-295-2437
Kurt@LangoHanson.com
Murase Associates
Portland: 503-242-1477
North American Wetland Engineering
Forest Lake, MN: 651-433-2115
Nawe@visi.com 
PIVOT design & consulting LLC
Portland: 503-235-5429
eshriner@mindspring.com 
Rana Creek Habitat Restoration 
Carmel Valley, CA: 831-659-3811
Ranacreek@earthlink.net
Ranacreek.com
Roofscapes Inc.
Philadelphia, PA: 215-247-8784
www.roofmeadow.com
Schaber and Associates, Inc
503-655-8921
Kschaber@rci-online.org
www.Rci-online.org
Soderstrom Architechs, P.C.
503-228-5617
www.sdra.com
Lando & Associates, 
Landscape Architects
Portland: 503-233-6600
www.lando-
landscapearchitecture.com 
NURSERIES - SOIL PROVIDERS
Oregon Association of Nurserymen
503-653-8733
www.oan.org
Pro-Gro
Sherwood: 800-682-3501
www.pro-gromixes.com
Squaw Mountain Gardens
Estacada, OR
503-630-5458
hennchicks@aol.com
ADDITIONAL WEB SITES
www.Greenroofs.com
www.Enn.com 
www.Greenroofs.ca
www.ecoroofseverywhere.org
Dan Saltzman, Commissioner
Dean Marriott, Director
ECOROOFS
Questions & Answers
is available online 
www.cleanrivers-pdx.org
© 2000 Environmental Services, Portland, Oregon
503-823-7740
PL 0382 revised Oct 2003