MANSION EXPANSION

This building will soon be the city’s largest mansion.

Famed architect Maya Lin — who designed the Vietnam Veterans Memorial when she was just a 21-year-old Yale student — is the brains behind a 20,000-square foot single-family home being erected at 11 Hubert St. in Tribeca.

The plans, which were approved by the city’s Landmarks Preservation Commission, call for gut renovating the three-story building and adding two stories on top.

The building is about to hit the market for $35 million and it will cost another $15 million to develop, listing broker Andrew Azoulay, of Douglas Elliman, told The Post.

At 70 feet tall, 50 feet wide and 100 feet deep — with its own fourcar garage and 82-foot-long swimming pool — it will be the biggest suburban-style mansion the city has ever seen, Azoulay said.

It’s also the first home designed by Lin, who was a 2016 recipient of the Presidential Medal of Freedom, the nation’s highest civilian honor.

“Due to the size of the entertaining space, the crazy amenities, private parking and security, we know that this will be perfect for celebrities like Jay-Z, Beyoncé and their growing family,” Azoulay said.

The home also includes a high- speed commercial elevator, an interior courtyard, a basketball/ squash court, three kitchens and a rooftop terrace.

“A four-car garage is unique. Especially downtown,” said real-estate appraiser Jonathan Miller. “When you have a 50-foot-wide home with 100 feet depth, you have more options to create something unique. That’s what makes this unusual.”

The home will also include a security office and an entire floor below ground devoted to health and wellness.

The third floor will have a dining room overlooking the doubleheight living room, with a wine room, a library/study, a warming/ prep kitchen, a bar and bathrooms.

The fourth floor will have three “very large” bedroom suites with nearly 500-square-foot walk-in closets, full bathrooms and studies. There’s another laundry room on this floor.

The fifth floor will be devoted to a 3,000-square-foot master suite with a two-story walk-in closet with an internal staircase.

The mystery seller bought the building for $13.3 million from architect Winka Dubbledam in 2014, according to city records.

Lin showed up at a landmarks-commission meeting last June to present the plans herself.

“It’s hard to say no to her,” a source said.

THIS BOLD HOUSE: This property at 11 Hubert St. is being redesigned by architect Maya Lin and is slated to become the largest single-family home in the city. With five luxurious floors, including a four-car garage (bottom inset), the mansion is...