COMMERCIAL BUILDING SHELL ECOROOF

COMMERCIAL BUILDING SHELL ECOROOFSE 13th Avenue and Bidwell

PROJECT SUMMARY

Project Type New commercial, one-story, over modified bitumen water-proofing membrane

Ecoroof Type Simple extensive typeSoil Depth 3-1/2”Cost $39,461 ($9.89/sf) includes drain mat, root barrier, soil,

plantings & irrigationInstallation Date February 2010

This project involves the installation of an ecoroof on a new one-story commercialbuilding in the Sellwood neighborhood of Portland, Oregon. The 4679 square foot buildingis on a 5000 square foot lot. Because the lot shared property lines on two sides with lotshaving the same Storefront Commercial zoning, and the other two property lines frontedon public right-of-ways, the developer was allowed by the zoning code to develop the

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whole lot. The high cost of land in this neighborhood and the desire to preserve the urbanquality of the neighborhood, motivated the developer to maximize his building footprint.

The Sellwood neighborhood was originally developed about one hundred years ago, and isstill served by a combined storm and sanitary sewer. The rules pertaining to stormwaterdrainage design for new development in this area require that in the best case, allstormwater will be managed on-site and no additional run-off will contribute to the loadon the combined storm and sanitary sewer. This solution would require an on-sitedrywell or other stormwater facility large enough handle all of the roof drainage and injectit into the ground. On our site, there was no space for such a facility. Building astormwater facility under a building was determined to be bad long-term solution.

If it is physically impossible to dispose of all stormwater on site, the next best solution isto retain the water on site and release it slowly into the combined sewer. While there areother stormwater facilities that could have achieved this goal, the ecoroof seemed to bethe only solution that allowed us to develop the maximum floor area. The ecoroof alsohad other benefits. The developer owns the lot to the west, and is interested in possiblydeveloping a multistory residential building on the lot. The ecoroof will enhance the viewfrom the multistory building when looking over the one-story commercial building. It isalso expected that the ecoroof will reduce the solar heat gain on the building and thusreduce the electrical bills of the building’s tenants.


ROOF ASSEMBLY


PLANTS

Plantings were by broadcast Sedum cuttings at an application rate of 300lbs/1000sq.ft.. Ecoroof soil was thoroughly moistened prior to planting,then lightly rolled to help introduce the cuttings into the soil.


The planting inprogress, this photoalso shows the drainrock edging that wasused wherever themembrane wasturned up a verticalsurface.

24” x 24” precastconcrete paverswhere used toprovide access to theroof mountedmechanical units.


SOIL


IRRIGATION PLAN


PLANTING PLAN


ROOF MEMBRANE

The waterproofing membrane that was selected for this project was the Sopraline Flam250 GR. It is a 160 mil membrane that is torched to a 120 mil base sheet. This is a systemthat is designed for use as a deck water-proofing and it has a record as such. A decisionwas made early in the project to minimize the risk of leakage by using the best, affordablemembrane we could find that would be installed by a contractor with experience withdeck water-proofing.

When trying to choose an ecoroof system, we quickly learned that there were numerousoptions: pre-planted matte and containerized systems, planted on-site containers, andplanted in loose soil. The containerized systems were about $5 - $7 per square foot morethan a system that is planted on-site in loose soil. The loose soil system was chosen,recognizing that should there ever be a leak, it might be difficult to locate. For addedinsurance, we installed the Protectsys measurement grid under the water-proofingmembrane. It is a low voltage electrical grid that will allow the building management topinpoint a leak without disturbing the ecoroof. Due to the size of the roof, it was notpracticable to flood test the membrane prior to installation of the ecoroof.

Shown are two layers of rigidinsulation, the ProtectsysMeasurement Grid (silver,) and the1/4” Densdeck protection board.


ROOF STRUCTURE

The ecoroof is supported by a wood deck, consisting of 7/8” tongue and groove plywoodover 26” deep open-web wood joists at 48” o/c. The building is approximately 50’-0”deep, and there is a column line at about the midpoint between the east and west bearingwalls. Between the tube steel columns there are 6-3/4” x 30” glu-lam beams. The roof isdesigned for a 25 psf snow load and a 32 psf dead load (including a 22 psf added for theweight of the ecoroof when saturated.) The roof deck slopes from east to west at a 2%grade.


MAINTENANCE PLAN


LESSONS LEARNED

It is still early in the process to evaluate the success of the project. I think everyoneinvolved in the project is confident that the ecoroof will pay dividends in the addedenjoyment of the future residential building to the west. It is also expected the water-proof membrane will serve the building very well for many decades, as it is protectedfrom the sun. However, tenants have now started occupying the three tenant spaces inthe building. A 6” exhaust vent was provided to each tenant space at the time of roofinstallation, to avoid penetrating the water-proof membrane after installation. We arefinding that the one 6” exhaust is not sufficient for all tenants, meaning that we have tofind creative solutions to avoid penetrating the roof.

COMMERCIAL BUILDING SHELL ECOROOF

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