The latest project of Hyatt hotel heir Anthony Pritzker is a 49,300-square-foot building designed by an architecture firm in Paris. It involves a small army of specialized consultants and boasts amenities like a bowling alley, hairdressing area and gym.

The project, in the hills above Los Angeles, isn't a luxury hotel—it's a private home for Mr. Pritzker and his family.

Four years into the housing downturn, what little new-home construction remains is focused on downsized living. According to the Census Bureau, the average size of a newly completed single-family home peaked in 2007 at 2,521 square feet, capping nearly three decades of growth, falling to 2,392 square feet in 2010.



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Then there are the exceptions, a small cadre of homeowners who are currently building mansions that are 10 times that size. Interviews with the small pool of luxury builders who handle such projects, and a perusal of permits in wealthy areas including parts of Connecticut and California, suggests that for some of the mega-wealthy, big is back.









In the fall of 2008, clients were saying, "It's not the right time to do the big house on the hill," says contractor John Sebastian, president of Dallas-based Sebastian Construction Group, whose current roster of projects in Dallas and Los Angeles spans 13,000 to 24,000 square feet. As those sentiments dried up, business has picked up, he says.

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Hedge-fund manager Cliff Asness is building a 25,900-square-foot, Colonial-style home with an indoor swimming pool and tennis court in Greenwich, Conn., according to permits and other town records. Nearby, a 31,500-square-foot mansion is being built for Lee Weinstein, founder of data-center concern Xand, with 15 bathrooms (plus additional powder rooms), a 2,500-square-foot master suite and a basement with a theater, wine cellar, juice bar, dance studio and sauna, records show. Twenty miles away, in Westport, Conn., Melissa and Doug Bernstein, whose Melissa & Doug company makes educational children's toys, are creating a compound of more than 30,000 square feet with a stand-alone ice-cream parlor, plans show. The main house alone is 29,500 square feet and includes a gym partially covered by glass; there's also a guest cottage, pool cabana and rec-room-and-garage building. The property also has a pool, tennis court and playground. The town deemed the home complete last summer; the tax assessor in 2010 valued the property at $19.8 million.

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In Silicon Valley, Jim Ellis, who co-founded a cellphone insurance provider, and his wife, Jenna, are building a 25,000-square-foot home on a single story. Plans show the home, which at 430 feet in length is longer than a football field, is expected to have multiple garages, including a showroom garage joined to a family room by a glass wall, allowing viewing of the car collection from inside the home.

In Incline Village, Nev., software mogul Larry Ellison's 18,000-square-foot-plus compound under construction will have competition from a neighbor's house down the street. Plans show a more than 50,000-square-foot lakefront home, including spaces such as decks; inside the home, plans show a half-basketball court, trampoline, climbing wall and indoor tennis court with a viewing area. The owner is Gene Pretti, who heads an investment-management firm. The owners of the homes identified in this story, some of whom own their property through limited-liability companies, declined to comment or did not respond to requests for comment.



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At this rarefied stratum, luxury builders say emotion and desire often drive demand. "You don't need that much space," says a Dallas businessman who recently completed building a 28,000-square-foot home for himself and his family. He says he and his wife planned to build a roughly 13,000-square-foot home, but their plans just kept on growing. "The architect was a really good salesman, [and] we just kept dreaming, I guess." Builders say owners are building their dream home or building for more or older children, and renovating an existing property, even extensively, might not satisfy their checklist.



That checklist, permits and architectural plans filed with local municipalities show, can be long, and creative. Builders tick off other amenities like shooting ranges (good ventilation is key to avoid inhaling contaminants), underground tunnels (they allow easy access to other buildings on the property), underground garages (they don't obstruct views) and panic rooms. "You'd be amazed at what some creative minds come up with," says Peter McCoy, whose Los Angeles-based construction firm, Peter McCoy Construction, is building Mr. Pritzker's home. Mr. McCoy declines to discuss individual clients.





In Los Angeles's tony Brentwood neighborhood, the 18,300-square-foot limestone home of New England Patriots quarterback Tom Brady and supermodel Gisele Bündchen is reached via bridge over a pond that separates it from the driveway, according to plans filed with the city of Los Angeles. The master suite has his-and-hers closets, both with skylights, and the master bath connects to an outdoor bath area with a saltwater plunge pool and shower; a covered walkway connects the rest of the home to a 1,590-square-foot gym with skylights over a garage. The first floor includes a playroom, service kitchen, library with terraces and a "morning bar." According to plans, the property also has a pool, spa, pool house and a playhouse.

One obvious drawback of building big: unwanted attention. Neighbors sometimes chafe at the idea of an edifice down the street the size of the White House. Reacting to McMansions that went up in the housing boom, some communities, like Chevy Chase, Md., passed rules that regulate more strictly how big houses can grow, says John McIlwain, a senior resident fellow specializing in housing issues at the Urban Land Institute.

Near where Mr. Pritzker's home is under construction, neighbors are up in arms over another of Mr. McCoy's projects, a roughly 70,000-square-foot compound (downsized from 85,000 square feet) awaiting permitting for Prince Abdulaziz ibn Abdullah ibn Abdulaziz Al Saud, son of the king of Saudi Arabia. The compound is on three lots and would include a main home of 42,000 square feet—part of it underground—a guest house, pool cabana, gate house and another residence of up to 20,000 square feet. The prince's lawyer, Benjamin Reznik, notes other residences in the neighborhood are super-sized and says opposition has been "fomented" by neighbor Martha Karsh, the wife of Oaktree Capital Management founder Bruce Karsh. Ms. Karsh has hired publicists to attract attention to the project, he adds. "Newt Gingrich wishes he had that campaign going," says Mr. Reznik.



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George Mihlsten, a lawyer for a community coalition and Ms. Karsh, says the coalition hired his firm and that Mr. Reznik has hired outside help too, including a community-relations firm (Mr. Reznik says that was in response to Ms. Karsh's campaign). "He likes to focus on Martha, but the truth is he and his client have created the controversy by proposing an outlandish plan and going behind the backs of the community to try to get it built," Mr. Mihlsten says in an email, likening the scope of the project to a small community shopping center. More than 1,500 residents of Benedict Canyon signed a petition expressing their opposition to the project as it was originally proposed, according to a representative of the coalition.

The scope of these projects makes them extremely complex to construct. Finding or assembling the property can take several years, and the design and construction of a super-size project can take up to five years or more, builders say. (These days, lower labor costs in some areas can mean quicker turnaround times or better value.) Just finding parking for the 100 to 200 tradespeople that can be on-site for a big job, compared with the eight to 20 people typically working on a 4,000-square-foot home, can require planning; commandeering church parking lots is one standby.

In addition to a general contractor, a 40,000-square-foot home construction might involve a design architect from out of town who comes up with the conceptual design; a local executive architect who deals with the builder; an owner's representative; a structural engineer; a landscape architect; a landscape attorney; an interior designer and acoustical, lighting and waterproofing consultants.

"Every 5,000-square-foot mark, a house becomes something different," says Scott Hobbs, president of New Canaan, Conn.-based Hobbs, Inc., whose firm is building Mr. Asness's home. (Mr. Hobbs declines to discuss individual clients.) At 20,000 square feet and above, he says, a house is more akin to a commercial than a residential project, requiring industrial components that are tucked away so the home still feels inviting. Builders say golf carts for traversing estates and elaborate security systems for keeping tabs on inhabitants are part of the picture, too, at this scale.

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On a late Los Angeles afternoon last fall, up a steep and winding road in lower Benedict Canyon, a covered chain-link fence and a dense covering of trees and shrubs blocked most views of the mansion of Mr. Pritzker, part of the Chicago real-estate family and a billionaire co-founder of private-equity firm the Pritzker Group. Workers walked around the property and glimpses of windows, a staircase and materials like ladders and beams were visible. "All visitors much check in with security," a sign at the entrance to the property read.

Plans filed with the city of Los Angeles, which deemed the mansion finished in November, provide more details. The 49,300-square-foot, two-story home surrounds a courtyard and includes a two-level basement with amenities including a game room, bowling alley, bar and media library. Above ground, there's a gym with changing rooms, his-and-hers offices, an arts-and-crafts room and a hairdressing area. Other buildings on the property, including a detached recreation room and a guest house, bring the total square footage of the compound to just over 53,000 square feet.

The home has a large skylight, roof-mounted solar panels and a curving driveway. A lawn spreads around part of the home, with a "floating pool" and spa anchoring one end of the property.

Critics of such mega-mansions "want to penalize people for being successful," says Mr. McCoy, the builder of the estate. Referring to the scores of people large projects employ, he adds, "People have done this all along because they could, and aren't we lucky that they can?"

—Sarah Tilton contributed to this article.

Write to Juliet Chung at juliet.chung@wsj.com