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Rooftop Renovations
How to Overcome the Challenges in Building One

The Central Park West penthouse has a 500-square-foot lower walled terrace. Easter Redbud and Kousa Dogwood trees are situated in lightweight planters. Located at the bottom of the photo are Lantana camara perennials. Wrapped around the building's elevator shaft (right) is a recirculating fountain made of powder-coated aluminum and steel framing with a gray patina. A small pipe feeds the water into the planter basin underneath the black body. Because the water eventually evaporates, replenishment is needed. A pump drives the water up through the fountain and then cascades down. Since the project was located on the rooftop, the materials had to be lightweight, transported in sections and assembled on-site.


The trellis screening, bench and deck are primarily made of weather-resistant ipe wood. Boston Ivy and English Ivy cover the screening. The floor consists of thin granite pavers on a rigid black backing.

A rooftop garden or terrace can serve as a natural extension of a New York City residence and can be a place to relax and retreat from urban life. A successful rooftop installation needs to factor in many considerations including weight restrictions, how the furniture is assembled, wind and weather conditions, plant selection, and irrigation - to name a few.

When Gunn Landscape Architecture designs a rooftop project, they pay special attention to the live load of the materials that are placed or built onto a terrace. Determined by a structural engineer, the live load is how much weight a roof or terrace can support that consists of movable objects, people, and loads created naturally by the environment, as opposed to structural elements, like the beams that are part of the roof's foundation. Lightweight pavers and faux-stone planters (rather than real stone planters) are some examples of materials that can help reduce the live load.

Gunn also ensures that they select furnishings and planters that are easier for sister company Vert Gardens to install on their projects. These tend to follow a modular system of installation on a rooftop. Long planters that border a roof garden won't fit into a service elevator unless they are transported in sections to the site, where they would have to be assembled to form a complete set. Sometimes, hoisting materials is necessary too.

Another aspect of a live load is water-whether that comes from standard irrigation or rain. To ensure that roof gardens stay properly hydrated but minimize the amount of water on the terrace, Vert Gardens often installs paving on a pedestal system for proper drainage, and uses Xeri-Bug Emitters in planters and pots.

New York City rooftop projects that Vert Gardens has installed include: two Central Park West terraces and two Chelsea terraces that are connected to their respective penthouses, and a wrap-around terrace for a SoHo penthouse. Each project took about four to six months to complete with a Vert crew of about six to ten people.


Pavers with a scarpalleto finish cover the floor of the lounge. On a drainage mat and pedestals, these 12" x 24" pavers were applied with a clear sealant. Integrated into the steps of the terrace, the water feature is highlighted by LED strip lights that are underneath the steps. Vert also installed in-ground lights by each plant pot. Because of the glass windows, the outdoor space is also illuminated by the interior lighting that projects outward onto the terrace.


The Soho Penthouse has a dining area; the table, built-in-seating, and flooring are made of ipe wood. Basket Willow grows over an aluminum framework, providing a natural covering.

Central Park West Penthouse
The Central Park West penthouse features a 500-square-foot lower walled terrace and 118-square-foot upper tower roof deck. The clients wanted the lower terrace to have a private garden surrounded by trellis screening covered with Boston Ivy and English ivy, where they could spend time reading and relaxing. As the roof deck is more of a balcony overlooking Central Park, simpler furnishings and grasses were installed to focus on the pleasant views from above.

One of the biggest challenges on this project was transporting up all the materials in a narrow service elevator, and this had to be factored into all aspects of the project. The screening, built-in seating, and decks had to be constructed on the lower terrace. The clients wanted a water feature that would wrap around the elevator shaft, so Gunn designed a cascading fountain. The fountain was transported through the service elevator in sections and installed as a complete unit on-site.

One of the other key challenges of this project was keeping the live load to under 40 pounds per square foot for this pre-war residential building. The clients wanted to create an urban oasis that felt like a garden on a rooftop. Along with the ivy-covered trellises, they also wanted to bring in trees. The chosen Eastern Redbud and Kousa Dogwood weighed 500 to 600 pounds each. Vert Gardens had to compensate by using more lightweight materials. By sourcing planters that looked like real stone, but were actually cast in molds from resin with marble dust, Vert Gardens was able to reduce the weight load.

In addition, lightweight, thin granite pavers on a rigid black backing were installed 1/8 of an inch apart on a pedestal system. The pavers complemented the ipe decking, which only covered 20% of the terrace's surface, as it was a combustible material.


This custom stainless steel spa can fit four to six people. The plumbing is separate from the terrace's irrigation system and was built to hold a total weight of 5,230 pounds of water. For safety reasons, a glass railing was added along the ipe deck. The piping equipment is underneath the steps of the ipe decking and the settings for the spa can be adjusted from a control panel. Located underneath the spa, a drainage mat collects and channels excess water into a drain hole in the terrace's foundation. This is done through the paving on a pedestal system. The spa also has a retractable cover.


The north side of the Chelsea Terrace is 621 square feet with furnishings that were transported through the service elevator and built on-site, like the Central Park West Project. The planters are made of ipe wood and the ground of Basaltina stone pavers.

SoHo Penthouse
The most prominent aspect of this 1,987-square-foot SoHo terrace is its willow structure. As the penthouse is high up, Gunn designed a natural shade cover for this rooftop. Vert Gardens planted Basket Willow in planters and trained it to grow over an aluminum armature. Planted in lightweight faux-stone planters, the willow whips received a 'sculptural' gardening treatment from Vert. They were pruned and woven together to grow into a canopy shape. A custom teak table and ipe built-in seating completed this dining area, which has a spa to the left of it, and another lounge area to the right. Around the corner from the lounge, this L-shaped terrace has another open space where the owners could relax and socialize with their guests.

For this project, rather than use a service elevator, Vert hoisted the spa from Diamond Spas to the penthouse of the building as it was too large to fit in the elevator. To do this, Vert obtained permits from the NYC Department of Buildings and Department of Transportation to close off nearby streets and raise the spa over the rooftop.


Included on the terrace is a weathered zinc fountain with ipe wood framing. It is connected to the main irrigation system; a small tube fills the bottom of the fountain with water and then recirculates. Periodic replenishment is needed because the water eventually evaporates. A pump transports the water to the top and five spouts release the water. Set on an automatic timer, a spaghetti tube replenishes the fountain. The trees above are Crape Myrtle.

Chelsea Terraces
For the award-winning Chelsea project, Vert built an urban oasis on the 621-square-foot north and 543-square-foot south terraces on either side of the rooftop penthouse. The client was keen to block some views where they were overlooked with planters and plantings, but allow views of landmark surrounding buildings. These discrete outdoor 'living rooms' were designed by Gunn to maximize space and allow flexible options for entertaining, dining, and relaxing. Ideally suited for dining and entertaining, the north terrace supports a rich mix of trees, shrubs, and climbing vines in planters made from ipe, and lightweight pots made from fiberglass. An upholstered ipe banquette and other furnishings separate the dining and lounge areas. The clients wanted to be able to cook on the quieter south terrace. As building codes will only allow a grill on the terrace, Vert Gardens installed an outdoor kitchen with a stainless steel grill, as well as an ipe cabinetry, an icemaker, and Glacier Blue Devonian Sandstone countertops and backsplash. Across from the barbeque area, a weathered zinc fountain was integrated into ipe framing that resembled the planters on either side of it. The water feature was further reinforced with under plantings that blended into the rest of the planting plan on the terrace.

Building management was concerned about the weight and size of the planters as the live load had to be maintained at under 100 pounds per square foot. Vert Gardens used lightweight soils (45lbs/ft) and a drainage layer under the soil to reduce soil weights. Additionally, most of the planters didn't have paving underneath, and were removable. The foundation for both terraces incorporated Basaltina stone pavers.

For all three projects, Vert Gardens built in an automatic drip irrigation system set on a timer so to make garden maintenance easy for clients. All the plumbing and electrical equipment was placed into the back of custom seating or cabinetry so that it's not readily visible but can still be accessed easily if needed.

As seen in LC/DBM magazine, June 2018.

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June 19, 2019, 11:00 pm PDT

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