Fast-rising Mint Museum apartment tower recipe: Pour concrete, cure, repeat

Construction workers ready the 32nd floor of the Mint Museum apartment building in uptown Charlotte on Thursday December 3, 2015.
Construction workers ready the 32nd floor of the Mint Museum apartment building in uptown Charlotte on Thursday December 3, 2015.

Thirty-two floors above the bustle of uptown Charlotte, a cold wind whips workers getting ready to pour the latest floor of a new luxury apartment tower being built on top of the Mint Museum.

They’ll finish the floor in three sections, with a pump that snakes down to ground level to suck up concrete and pour it up in the sky, through a nozzle that faintly resembles an elephant trunk. Developer Childress Klein and general contractor Batson-Cook are building one floor every four days, a pace they’ll continue until the tower is finished.

Meanwhile, on the floors below, other workers are framing the rooms, installing electrical and plumbing systems and sheathing the tower in floor-to-ceiling glass.

I toured the Mint Museum apartment tower at 525 South Church Street this week to answer one of the most frequent questions I get about the project from readers: “How are they building it so fast?”

Part of the trick: Most of the necessary prep work was done years ago, before the project was put on pause during the recession. The structure to support the Mint Museum tower was put in place inside the museum during the building’s construction in 2009. But the recession and its lingering aftermath tanked condo sales, and when the Mint Museum opened the residential tower was on hold.

Now, Childress Klein has revived what was originally planned to be a luxury condo tower as apartments, a sign of the strength of the apartment boom.

“It’s been sitting dormant,” said Fred Klein III, a Childress Klein Partner, standing in the empty shell space behind the Mint Museum. The smell of coffee drifted in through the insulation of a shared wall with Starbucks. The space has been vacant, waiting to be transformed into a lobby for the tower, for years.

The Mint Museum was designed to support a tower atop it from the beginning, when the building was constructed as part of an arts-and-office complex started by Wachovia before the Charlotte bank faltered and was purchased by Wells Fargo. The city and county contributed to the project, which included the office tower that became the Duke Energy Center, with a 2006 tax rebate agreement.

“The team did a good job planning for residential later,” said Randy Thompson, project executive for Batson-Cook.

Crews started work on the tower in May, and plan to finish the 394-unit luxury project in a speedy year and a half. The temporary elevators attached to the side of the building had ready-made ties to anchor into, one of many perks of starting a project with much of the prep work done in advance.

Still, the site poses challenges. With no staging or storage areas, Batson-Cook unloads supplies from delivery trucks in a lane of Church Street, causing traffic headaches. Concrete trucks park under a protective steel frame built over the Levine Avenue of the Arts, which is closed for the duration of construction. Workers build the forms to support and shape the concrete atop the protective covering, since they don’t have any other space to do so.

With Charlotte in the midst of a record apartment boom, developers are racing to finish projects as a bumper crop of high-end apartments in and around uptown gets ready to hit the market. There are more than 12,300 apartment units under construction and another 13,500 more planned, according to Charlotte-based Real Data.

“You don’t know when the market will turn, so you want to get it leased,” said Klein. And the expenses of building the project only increase the longer it takes, so a quick timeline is always beneficial for developers.

Klein said rents are excepted to be over $2 a square foot (that’s $2,400 a month for a 1,200 square-foot apartment, for example), which would be among the highest in the Charlotte region. Childress Klein’s Element apartment tower nearby has been able to sustain similar rents, Klein said. A 625-square-foot studio in Element is currently listed for $1,405, or $2.25 per square foot.

Childress Klein bought the air rights to build above the Mint Museum earlier this year from Wells Fargo for $18.1 million. Klein said the developer plans to keep the units as apartments, not convert them to condos. About three quarters of the apartments in the Mint Museum tower will be studio or one-bedroom units.

Most time-consuming work done in advance

You can see how long digging foundations, driving pilings and building the supports needed for a high-rise takes in another project a few blocks away: 300 South Tryon.

Workers at the office tower being developed by Spectrum Properties have spent the past year digging a 45-foot deep foundation and building the structure’s base for a year. The structure is just getting back up to street level.

By comparison, pouring concrete floors is relatively quick.

“It’s a repetitive action,” Batson-Cook superintendent John Bai said of pouring concrete, standing atop the 32nd level. Each concrete section is poured atop a “table” that workers use a crane to slide into place. After the concrete cures, workers slide the table out, move it to the next section and repeat the process.

“We’ve got a good sequence,” said Thompson. “Everyone cycles through...It just kind of crawls up the building.”

At 43 stories, including the Mint Museum below, the tower will be Charlotte’s second-tallest residential building, behind the 51-story Vue building on North Pine Street.

To coordinate with subcontractors, supervisors meet daily in a “war room” with jobs mapped out day by day, four weeks in advance. Every wall is covered with a rainbow of multicolored notes showing what everyone is supposed to be doing each day. Contractors only have four days or fewer worth of supplies on hand, so every stage of work must be carefully choreographed.

“The planning part is huge,” said Thomas.

Ely Portillo: 704-358-5041, @ESPortillo

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