Construction of the 60-story Millennium Tower in Downtown Crossing included 61,000 cubic yards of concrete. Photo courtesy of Lou Jones.
For decades, Boston was known as a “steel town,” or a city whose new high-rises were more often built and framed with steel.
The familiar “skeleton” frames – made famous over the years by spectacular photos of steel workers dangling from steel I-beams or even eating lunch high above city streets – have been employed on numerous office-skyscraper projects in Boston and elsewhere.
But in recent years, Boston has also seen a residential building boom, as new luxury apartment and condominium towers go up to meet the seemingly insatiable demand for more housing in the region. With those new residential towers has come an innovative, at least for Boston, construction technique: poured concrete.
Instead of steel skeleton frames, poured concrete means just what it says: The entire inner core, floors and weight-bearing columns of towers are made out of concrete. It’s a technique heavily used for years in New York, Chicago, Miami and other cities where residential-tower construction have long been the norm.
Now the method, steadily adapted and improved over the years, has been used for a slew of recent and current residential projects in Boston, including the Millennium Tower at the site of the old Filene’s department store in Downtown Crossing, the Four Seasons Hotel and Private Residences at One Dalton St. in Back Bay, the 131 Beverly St. luxury condo tower in the North Station area, and other ongoing and planned residential projects.
“It’s become much more common in Boston,” said Darren Messina, head of design and construction at Carpenter & Co. Inc., developer of the One Dalton project under construction in Boston’s Back Bay. The 61-story Dalton, which is expected to be completed by 2018, is being built and framed via poured concrete.
“It’s an innovative and efficient construction method,” said Brian Radomski, vice president of construction at Related Beal, developer of the 17-story 131 Beverly project along Lovejoy Wharf. The 161-unit complex is scheduled for completion in 2017.
A Series Of Trade-Offs
Like every building technique, both steel construction and poured concrete have their pluses and minuses.
By far, the biggest advantage of steel construction is that it costs about $8 per square foot less than poured concrete. Because it’s been long and widely used in Boston, there are also more skilled steelworkers and experts in the field here.
And, arguably, a steel frame can be constructed faster than poured concrete.
But the advantages of poured concrete are numerous. Perhaps most importantly, it provides more flexibility in floor-plate designs, a key for residential projects in which multiple units of varying sizes and shapes lie on individual floors. Concrete is also better for containing sound, reducing a tower’s sway and providing higher ceilings, three other key features that appeal to residential builders and residents alike.
Though actual steel frames can generally be put up faster, poured concrete, once dried, allows subcontractors to start working on lower floors even as the upper floors are being constructed above. For steel, the frame generally has to be fully constructed before most subcontract work can commence.
Boston-based developer Related Beal is using poured concrete for the construction of its 131 Beverly luxury condo complex at Lovejoy Wharf.
“Poured concrete allows crews to work at a more rapid pace,” said John Newhall, a project manager at Boston-based Suffolk Construction, which is the construction manager for both the Millennium Tower and One Dalton St. projects. S&F Concrete Inc. of Hudson was the concrete subcontractor for the Millennium Tower, while G&C Concrete Construction Inc. of Haverhill is handling One Dalton.
The 60-story Millennium Tower Boston project was topped off last September and its general statistics are almost mind-boggling: 1.2 million square feet of horizontal construction and 61,000 cubic yards of concrete (including 6,000 cubic yards for its base mat, the largest continuous concrete placement in Boston’s history). And, yes, there was still plenty of steel involved: 10,000 tons of reinforcing steel and 410 steel plate link beams (equating to 850 tons of steel).
Floor by floor, the Millennium Tower’s concrete frame rose higher each week. And, floor by floor, subcontractors, ranging from plumbers to dry-wall installers, were allowed to dive into their work on the most recently completed lower floors.
“As a general rule, we like poured concrete on our residential projects,” said Kathleen MacNeil, the development project manager at Millennium Partners, which also used poured concrete for the residential north tower within the Ritz Carlton complex that Millennium built along Tremont Street in the late 1990s. “It’s really driven by our desire to create very special residential spaces.”
The question moving forward: Has poured concrete become a permanent mainstay within the Boston construction community?
Ultimately, the answer depends on how long the current residential-tower boom lasts, industry experts agree.
“In the past, Boston has been considered a steel town,” said Suffolk’s Newhall. “There simply weren’t as many high-rise residential towers going up. But that’s changing. In the residential market, I think you’ll see more (poured-concrete) projects here and elsewhere.”
