Living Roof Helps Orcas Island Home Blend into the Landscape

This residence on Orcas Island is crowned with an extensive green roof from XeroFlor.
Photos: Terra Firma NW LLC

Orcas Island is a horseshoe-shaped island in the northwest corner of the state of Washington. With an area of 57 square miles, it’s the largest of the San Juan Islands, and accessible only by ferry. When a client approached him about building a custom home on the island, Justin Paulsen jumped at the chance. Paulsen is the owner of Terra Firma NW LLC, a general contractor located in nearby Eastsound, Washington. “We were hired directly by the owners to build the project from the ground up,” Paulsen notes.

The 3,400-square-foot home features 3,850 square feet of roof area, which is crowned with a living roof. The system specified for the project was a XeroFlor extensive green roof, which was installed on top of a PVC membrane roof manufactured by Versico.

The green roof system consists of a root barrier with a drainage composite, 1-1/4 inches of growing medium, and pre-vegetated sedum mats. The system was installed in the late fall in 2018, so many of the plants were dormant. Photos: Terra Firma NW LLC

“The roof system works well for the home, which is designed in the style of the Bauhaus school of design,” notes Paulsen. “The home features many linear design elements, and the green roof gives it a sense of blending in with the natural surroundings.”

It was only the second green roof Paulsen had been involved with, so he made sure to do his homework. He knew from experience that work on the island would pose logistical challenges, so he tapped a talented to team to help design and execute the project.

The Roofing Contractor

Paulsen wanted a skilled roofing contractor to install the waterproof layer beneath the green roof system. The Versico rep in the area, Ken Stillwell, recommended All Weather Rooftop Solutions, headquartered in Everett, Washington. The company, owned by partners Todd Severson and Greg O’Neill, typically focuses on commercial work, but this project was right in their wheelhouse. Severson knew the company had to plan ahead to ensure the everything went smoothly.

Crews from Terra Firma NW installed the green roof system. The sedum mats arrived on a pallet and were unrolled on top of the growing medium. Photos: Terra Firma NW LLC

“Working on the island was the biggest challenge of the whole project,” Severson notes. “We wanted to complete the project in one week, so we had to make sure we had everything ready to go. Everything had to be transported by ferry, so we had to schedule all of the trucks and make sure all of the material landed at one time. We just had to make sure we had all of the material and manpower on that ferry.”

The PVC roof system was installed over a plywood deck. Crews first installed two layers of 3.3-inch insulation to achieve an R-value of 38. Tapered insulation system was then added to ensure proper drainage. The insulation was topped with half-inch DensDeck Prime cover board, which was mechanically attached. A gray 60-mil PVC membrane from Versico was then fully adhered over the entire assembly.

All Weather crews also installed OMG SpeedTite roof drains with Vortex-breaker technology, as well as Solatube light tubes. The large skylight was installed by the manufacturer, CrystaLite.

All Weather Rooftop Solutions installed the PVC membrane to provide a waterproof barrier beneath the green roof. Photos: Terra Firma NW LLC

The sheet metal work was completed by All Weather on a second trip, with a smaller crew returning to complete the flashing and edge metal. The roofing portion of the project went smoothly. “Justin from Terra Firma was great work with, and our superintendent, Jeff Gale, did a great job quarterbacking it on our end,” Severson notes. “Everything went off without a hitch. It’s a pretty unique little structure.”

Paulsen agrees. “They did a great job installing the insulation and the membrane,” he notes. “The biggest thing we had to deal with after that was protecting the membrane from other trades. Our stonemason had to go back up on the roof and complete the chimneys.”

To preserve the integrity of the membrane after it was installed, Terra Firma crews cut a 20-mil pond liner pond liner into sections that were used to protect areas of the roof that had to be accessed by other trades.

Installing the Green Roof

After all the other work was completed on the rooftop, crews from Terra Firma installed the green roof system in the late fall of 2018. Paulsen had heard about XeroFlor from another contractor and did some research. He then contacted Clayton Rugh, director of XeroFlor America, to design and specify the system.

“I thought it was really top-notch system,” Paulsen notes. “I went to Clayton to document some other examples that had been installed in the area, and I pitched it to our client. Clayton did all of the functional engineering work on the green roof system and determined the soil requirements. The plantings by XeroFlor were sourced very close to the project site, which helps to ensure successful future growth.”

Photos: Terra Firma NW LLC

The extensive green roof system consists of a root barrier with a drainage composite, which is an open-flow zone of polymer coils with a bonded fleece fabric sheet. The drainage material was topped with 1-1/4 inches of growing medium, followed by 1-inch-thick pre-vegetated mats, which contained a mix of sedum succulents.

The pre-vegetated mats are installed just like sod. “They arrive rolled up on a pallet,” Rugh notes. “You just align the roll adjacent to the previously installed roll, abutting it tightly, and roll it into place.”

Terra Firma also installed the edge metal and rock ballast around the perimeter. “I was amazed at how simple it was to accommodate the green roof portion of the project,” Paulsen says. “Once the membrane was down, we knew we were rock solid and the house was well protected. The green roof portion was easy to install. I’d definitely do one again.”

Paulsen is proud to have this project under his belt. He can’t wait to see it in the spring, when the green roof is in its full glory.

“Terra Firma NW thrives on jobs that have complex and unusual requirements,” Paulsen says. “This job, from foundation all the way through the roof, presented numerous design challenges. We have a $2 million-dollar house under this roof. If I had to give advice to anyone doing a green roof, my advice would be: Don’t cut corners.”

TEAM

Architect:  Harlan Pedersen AIA, Orcas, Washington

General Contractor: Terra Firma NW LLC, Eastsound, Washington, www.tfnwllc.com

Roofing Contractor: All Weather Rooftop Solutions, Everett, Washington, www.allweatherroof.net

MATERIALS

Extensive Green Roof System: XeroFlor XF + GM Assembly, XeroFlor North America, www.xeroflornorthamerica.com

Roof Membrane: 60-mil PVC, Versico Roofing Systems, www.versico.com

Cover Board: DensDeck Prime, Georgia-Pacific, www.densdeck.com

Skylight: CrystaLite, www.crystaliteinc.com

Daylighting: Solatube, www.solatube.com

Roof Drains: SpeedTite roof drains, OMG Roofing Products, www.omgroofing.com