US: The challenges of building a commercial rooftop greenhouse

Where do you put a commercial greenhouse in a crowded urban sprawl like New York City? Gotham Greens found a solution by building their first greenhouse in 2011 on a rooftop in Greenpoint, a Brooklyn neighborhood. They’ve since opened a second rooftop structure in Gowanus, Brooklyn, with a third due for completion early this year in Queens NY. 

Supplied by US greenhouse constructor Nexus Corporation, rooftop greenhouses are not only a great way to grow local produce, but also make better use of wasted spaces, which are often in communities that don’t have easy access to freshly grown produce.


Jeff Nexus, VP of Sales at Nexus.

But it’s not without its challenges. “Every building is different,” says Jeff Warschauer, VP of Sales for Nexus, “and the problem with building on rooftops is all the initial unknowns.”

An ideal scenario is the Arbor House built on a low-income apartment complex in the Bronx. “From the beginning of the idea it was designed and built to accept the greenhouse… That was probably the simplest rooftop greenhouse construction ever done.”

According to Jeff, it started out as greenhouses for institutions like the University of Connecticut and Florida State, but it’s now commercial growers who want to put greenhouses on rooftops.

Before anything can happen clients need to hire local engineers and architects to investigate building codes, building zoning, local ordinances and regulations and even potential neighbors’ complaints.

“What happens when all the grow lights go on at 9pm and it looks like a night time landing at Schiphol Airport? Is that going to be an issue?” says Jeff.


Gotham Greens greenhouse on Whole Foods Market during construction. Gotham Greens built and designed their own rooftop greenhouse.

Landlords have to be approached if a company wants to build on their roof and buildings need to be swiftly analyzed to make sure it can handle the loads; which is relatively light at five or six pounds per square foot for the greenhouse. "Keeping in mind that this load is dispersed over a large area, alternatively other loads may be greater and require different design criteria. Think about water tanks that may be 125 to 150 lbs per square foot so that tank area will need special supports to disperse the loads over a greater area."


Gotham Greens greenhouse on Whole Foods Market. Gotham Greens built and designed their own rooftop greenhouse.

Then there’s the zoning process and the mechanics of making sure you can get water, gas and electricity to the roof.

“You have to be sure you can do it not only technically, but logistically.”

On a roof like Arbor House, Nexus licensed engineers, who specialize in rooftop greenhouse design, closely worked with client developers and design teams so the greenhouse dimensions worked with the new building design and to be sure all would fit as per the design plan.

“That left us with a beautiful foundation on the same footprint as the greenhouse so when we got there it was a perfect fit."

Safety considerations are also paramount and most of the greenhouse roofs are made of polycarbonate or tempered glass, and are built to withstand inclement weather.

“As an engineering company, we find a big part of what we bring to the client, from working with a great commercial grower such as Gotham Greens, are listening to their needs and to assist the prospect of the best structure and equipment technology options as well as design, operational and construction options.” Jeff said.