A Deck Doesn’t Have to Be a Roof’s Worst Enemy

Board member Yan Courtois owns one of the three top-floor units in a walk-up co-op in Morningside Heights. “You have to walk up five flights to get there,” he says. “It keeps you extremely fit, but once you’re up there, you get the reward: a beautiful outdoor space with views of the city.”

Now Courtois’s 10-by-10-foot rooftop terrace is becoming even more beautiful. The owners of the three top-floor units are having new decks installed, and the technology of these decks is ingenious. “It’s called a pedestal paver system,” says the project engineer, Noah Manny of Cowley Engineering. “It’s superior to other deck coverings in many ways.” 

First, such a system consists of tiles set on several small, adjustable pedestals, which sit on top of the roof membrane – without puncturing it. This reduces the possibility of leaks. The adjustable pedestals also make it possible to level the deck several inches above a sloping roof. (All “flat” roofs are slightly pitched for drainage.) “We do this for all kinds of buildings,” Manny says. “Private and common outdoor spaces, large and small. It’s easy to install and the tiles come in several varieties. You can have a wooden, porcelain or concrete deck.” The tiles vary in size, too, ranging from six by six inches to two by two feet.

A paver system is not only easily installed, it’s also easily removed – a bonus when it comes time to repair the roof. “Without a paver system, you would normally have decking without any access to the roof membrane,” Manny says. “When there is a leak, you have to destroy your deck to make repairs. With this system, you just lift the pavers and do the repairs.”

Because the system is raised above the roof, it also allows for airflow. “With the air circulation, the expansion and contraction of the roof membrane is significantly limited, and the insulation’s thermal efficiency is maintained,” Manny says. “With traditional decks, you will have less efficient insulation.” Manufacturers, such as Bison or Hanover, also point out that pedestal paver systems allow water to drain from the roof, which is a critical issue for every building. 

“Weight is also an issue,” Courtois says. “With a pedestal system, the weight is better distributed, actually. It’s really common sense.” However, weight might become an issue. Before the pedestal paver system can be installed, an engineer has to determine if the roof can support the added load. According to Manny, the Bison system he’s installing at the Morningside Heights co-op requires a roof with a load-bearing capacity of at least 40 pounds per square inch. Each pedestal is able to support 750 pounds.

Most roofs will require that some tiles are customized. “Let’s say you have a rounded section, then the installer will cut those pieces to size,” Manny says. “That kind of cutting is usually done offsite to limit the amount of noise and debris on the roof, but it varies from project to project.” He adds that a paver system costs between $16 and $18 per square foot, depending on the size of the deck and the materials used. 

In Courtois’s co-op, the three top-floor shareholders are paying for their own terrace upgrades. “The new deck enhances the appeal of the top floor,” Courtois says. “I bought this apartment especially for the roof because I have a passion for bonsai trees. For me and my bonsai trees, this is paradise. It’s wonderful to sit out there with a beverage and my trees.” 

PRINCIPAL PLAYERS – ENGINEER: Cowley Engineering. MANUFACTURER: Bison Innovative Products.