When Frank Lloyd Wright designed the southwestern Pennsylvania home called Fallingwater, it was in concert with a waterfall and the surrounding mountain landscape. A Lake Geneva home patterned after that Wright landmark is now more imbued with nature, thanks to a TectaGreen roof designed and installed by F.J.A. Christiansen Roofing Co., Inc.

Like Fallingwater, the Lake Geneva home has multiple sections and terraces.
“This is a home with many distinctive qualities and with landscaping done in such a way as to appear very harmonious with the natural setting of mature hardwood trees, all rolling down to the Lake Geneva waterfront,” said Charlie Schulz, the FJAC project manager on the job.

But from the driveway leading to the home and from some of the home’s terraces, the view was of stone ballast over a multiple-car garage. It was an effective roof but a view that contrasted with the natural setting.
“The roof can be viewed from several terrace locations on this home,” Schulz said. “They wanted something more visually appealing than the ballasted EPDM roof.”

FJAC operations manager Greg Johnson noted that the owners also wanted a more aesthetically pleasing appearance from the approach to the house.
“This area is on the back side of the home, not the lake side,” Johnson said. “But it’s a focal point as you approach the home.”

The existing roof system, built on flat concrete prefabricated panels, was comprised of a 45-mil membrane with stone ballast over a wood fiber insulation separator. That was removed to the decking. A tapered polyisocyanurate insulation system was then installed. A premium-quality, 80-mil white PVC membrane was placed over the insulation, with drainage and filter components atop the membrane.

As is standard practice for roof systems that will bear a heavy overburden, the drains were plugged and a flood test was performed to ensure the integrity of the membrane. With the membrane passing the test, components of the green roof were added, starting with a drainage mat that also serves as a root barrier to protect the membrane.

Next came a filter fabric and then the engineered soil to support 1,350 sedum and thyme plant plugs. The plugs were arranged in a custom layout with the help of the owners’ landscape architect.

The original No. 2 stone ballast was recycled and used to create an 18-inch-wide perimeter “free zone” area of the roof, with a fabricated drainage bar to keep the ballast stones and soil separated. Free zones are a key design component for extensive, built-in-place green roof systems, as they prevent the plants from growing into the flashings and allow for easier maintenance where the roof needs it most.

The roof system was completed with pre-finished aluminum coping and counter flashing metal details.

While sedum is the common plant variety used on green roofs, thyme was included in the mix for this project to add fragrance that could be noticed in the master bedroom that overlooks the planted roof.

Another consideration in the plant selections was heavy shading.
The sedum and thyme should grow to cover 85 to 90 percent of the planted area by early next summer, which is a quicker fill-in than usual but which will be realized because planting density was slightly higher than normal. This year’s growth will primarily be in the root systems as the plants establish themselves.

“The green roof is a natural fit for this home,” Johnson said. “The aesthetics are really improved.”

The TectaGreen roof has more than aesthetic value for the home. “We expect the roof to be in place 30 to 50 percent longer than a similar conventional PVC roof,” Schulz said. That’s because the plants and soil medium shield the membrane from the deteriorating effects of the sun.

When you read or hear about green roofs, it’s normally about a commercial, government or institutional building. This project shows the value of green roofs for residences, as well.

“I expect that this roof will generate a fair amount of interest, given the high level of landscaping in the surrounding community,” Schulz said. “Residential green roofing is not common, but this shows how nicely it can complement the architecture of a home that has the structural capacity to support a green roof. The additional pervious space also further protects Lake Geneva from additional, unnecessary storm water runoff.”