Melrose Commons II, a 30-unit multifamily affordable-housing project in New York City, represents a new approach to designing these facilities. The homes feature an all-precast concrete design that the developer agreed to try after meeting with the precaster and being convinced of the benefits.
"We've been using hollowcore plank for floors and ceilings for years in similar units," explains the project's developer, Les Bluestone, a partner in MC II Associates and a veteran of building affordable housing. "Even so, initially it was a little bit of a leap of faith to go with all-precast construction. Ordinarily we would use masonry, but masons are very busy and high priced in New York City today. We also learned we could do some things in design with precast at a more affordable price than with masonry."
Sponsored By Housing Partnership
The 30 all-precast Melrose Commons homes nearing completion are part of an initiative to build affordable housing throughout the five New York City boroughs. The New York City Housing Partnership is the public/private not-for-profit sponsor that helps obtain subsidies from the city and state for the development of low-rise, multifamily homes. Each three-story, three-family home will have one owner, who will rent the other units for income. Containing approximately 3100 square feet, each building typically sells for $291,000. (Prices varied somewhat according to location, backyard size and other amenities.) An income of $43,000 was needed to qualify, according to Megan Black of the NYC Housing Partnership.
Oldcastle Precast Inc. in South Bethlehem, N.Y., fabricated the precast components for the all-precast design, which was created by Mike Smith of Equus Design Group in Belmont, Mass. He worked in conjunction with Danois Associates, which had created the original housing plan. The developer, architect and NYC Housing Partnership also provided input on the final design. But it was the developer who made the decision to use precast construction, according to Black. "His decision was partly based on greater construction speed with precast and the ability to build during the winter," she says. "The ability to provide more design details with precast also was a key factor."
Chicago Site Toured
As part of the decision process, Bluestone traveled to Chicago to tour an all-precast row house project, developed by Affordable Construction Concepts LLC in partnership with precaster Prestress Engineering Corp. The Chicago project used brick-like form liners on the exterior precast panels, but Bluestone wanted the appearance of real brick on his homes to fit with market expectations. The solution was to cast thin brick insets into the precast panels, combining them with precast elements resembling limestone. "With precast, we were able to incorporate elaborate cornices along with door and window trim details," he adds.
Window and door headers and sills and other limestone-appearing details were cast integrally into the panels. The base of the homes and their entry towers feature a precast pattern resembling blocks of limestone. The precaster used self-compacting concrete mixes in production to speed production and provide a high-quality appearance. Chase Precast in Worcester, Mass., a division of Oldcastle, was responsible for producing the architectural panels.
"The design of the homes reflects a need to respond to the traditional architecture of the neighborhood, which was brick with precast elements," says the developer's architect, David Danois of Danois Architects, New York. "Precast allowed us to express what we wanted. There were no limitations to what we could do."
Bluestone agrees with Danois' assessment of the flexibility precast allows in design. "The design potential with precast is really great. We're just beginning to scratch the surface of the possibilities," he says. "People's response has been very positive. Initially we were afraid they might regard the homes as concrete bunkers." An attractive rendering of the homes appeared on the cover of the sales brochure, and all the homes were sold prior to the beginning of construction.
Rated By Energy Star
The fact that the Melrose Commons homes are rated as Energy Star homes, using guidelines established by the Environmental Protection Agency's program, was an additional selling point. This means the homes are guaranteed to be at least 30 percent more energy efficient than homes built under the current model code. One qualification for such homes is that they have limited air infiltration. The precast system, with its solid panels, creates an almost airtight building envelope, according to Bluestone. The only joints are between floors and at the buildings' corners.
"This is an advantage over a typical masonry building where you have to rely on the masons' ability to make solid, tight walls with tight mortar joints without leaks and cracks," he notes. "The quality of a precast wall is consistent." It also requires little maintenance and resists moisture penetration better than real brick.
Construction is faster with an all-precast system, and erection of the building envelope can take place in any kind of weather. "Developers typically will finish their buildings three months sooner than with masonry construction," says Harold Messenger, Oldcastle's vice-president of marketing. "Saving time means saving money on interest rates."
Expediting Other Trades
One factor that speeds construction is that once the precast shells have been erected on a group of homes, the other trades can go in earlier and work vertically. Dimensions of the precast walls and floors are consistently accurate, allowing some interior assemblies to be premanufactured off-site. Some of these prefabricated possibilities include interior partition walls, plumbing manifolds, staircases, window and door sets, cabinetry and electrical subassemblies.
The all-precast housing system offers fire protection and sound insulation comparable to masonry construction. "But it is a much better system seismically, providing good structural stability," Bluestone says. "We have to meet new seismic codes in New York City today and need more reinforcement than five years ago."
Sequencing Is Key Challenge
The precaster's key challenge came in ensuring the right pieces were delivered to the site in the right order to ensure the proper sequence in erection, Messenger says. Erection began as soon as the poured foundation was ready. The basement was covered with hollowcore planks bearing on basement divider walls. After a few bays of plank were in place, the end walls and intermediate demising walls were erected. These walls support the upper story floors and eventually the roof structure.
All precast wall panels are 9 feet high and were produced in two lengths: 24 feet for the end walls and demising walls and 15 feet long for the front wall panels. When the floor plank and wall panels were in place, the entry tower sections were erected. Because of their large size, 30 feet tall by 8 feet wide, they were delivered flat and rotated into position. After the components were grouted and welded into place, the cornice sections surrounding the front and sidewalls of the homes were erected. Finally, the front stairs were placed. The cavity under the stairwell hides the electric and water meters from view.
Bluestone acknowledges that the project, which was begun in December 2001 and completed the following summer, has been a learning experience. But he is sold on the advantages. He is planning another housing project in New York City, consisting of 70 homes in a different design but again using the all-precast construction. And he already is producing material for Melrose Commons III, an addition to the project consisting of 40 more all-precast homes. The precast panels are in production now, with construction scheduled for completion by the end of October. "We expect everything will go even faster now that we know the process," he says.
Size: 88,200 square feet
Components: 130,000 square feet hollowcore floor and roof planks, 150 9- by 24-foot interior bearing walls, 60 9- by 24-foot exterior bearing walls with brick finish, 90 9- by 15-foot exterior non-bearing walls with brick finish, 30 U-shaped 30- by 8-foot entry tower pieces, 120 cornice pieces from 8 to 24 feet long and 30 front steps.
Cost: Approximately $12 million
Precast cost: $1.8 million |