In a ruling that angered Upper West Side activists and elected officials, Billionaires' Row developer Extell will be allowed to build a height-boosting "void"—several supersized floors intended to house mechanical equipment—as part of its planned luxury residential development at 50 West 66th Street.

All told, the contiguous mechanical void space in the building measures a total of 176 feet in height, almost half the length of a football field.

The Board of Standards and Appeals (BSA) on Tuesday voted 2-2 on a zoning appeal brought by Landmark West, a preservation group that said it examined drawings submitted to the city and found that less than 22 percent of the void designed for the 775-feet-tall condo project will be occupied by actual mechanical equipment. A tactic employed in recent years by several luxury developers in New York City, voids are designed to provided added height to buildings, making the residential units above them more valuable by enhancing the views.

At the start of the proceeding, one of the BSA's five members had abstained. In cases where the board reaches a split decision, the vote goes in favor of the developer.

Sean Khorsandi, the executive director of Landmark West, said he was upset not only by the votes in favor of the plan but also the city's tie-breaking methodology. The group had argued that the Department of Buildings failed to properly scrutinize the actual layout of mechanical equipment in the void space.

"I think it’s ridiculous that even in the case of a tie, the community loses. It’s a system that inherently always favors the developer," he said.

Khorsandi said he and members of the board of Landmark West will convene to consider its next steps. The group could elect to sue the city in state Supreme Court in what is known as an Article 78 proceeding.

Extell's mammoth void spurred city officials last year to pass new restrictions on mechanical voids. In May, the City Council passed legislation that calls for mechanical space exceeding a height of 25 feet to be counted toward a building's allowable floor area.

“Today’s split decision at the BSA shows how extreme Extell’s plans are and the danger mechanical voids can pose to other neighborhoods that could soon be blighted by supertall buildings," said state Senator Brad Hoylman, a Democrat who represents the area, in a statement. "It’s shameful that the BSA is allowing this project to still move forward."

Hoylman added that he backed state legislation proposed by Assemblymember Linda Rosenthal and Senator Robert Jackson that proposes to limit void space to 20 feet for the first void, and 12 feet for additional ones.

Gale Brewer, the Manhattan borough president, also issued a statement expressing her disappointment with the BSA decision, but added that she was "glad the board noted that the DOB must improve its procedures for reviewing plans, and ensure not only that developers comply with the building code but that they also adhere to the City’s zoning." 

She added: "We cannot continue to allow developers to flagrantly evade our zoning for their own benefit."

A spokesperson for Extell did not immediately respond to a request for comment. But at the public hearing in December, David Karnovsky, an attorney at the law firm of Fried Frank which is representing Extell, said the latest appeal is baseless and said that the developer acted in "good faith" prior to the zoning rules being changed.

Andrew Rudansky, a spokesman for the Department of Buildings, said, “We are pleased that BSA has upheld our permit, which was properly reviewed and issued."