In Dover, New Hampshire, a 138,000 square foot, five-level precast parking garage is being rapidly erected within two inches of a new steel-framed, two-story police station being constructed at the same time. The goal is to have the precast garage open before winter. The police station won’t be complete until early next year.
Erection of the police station had to start first, according to Andrew Martino, project manager for the contractor, Harvey Construction Company, because there is a common block firewall between the two structures that had to be built prior to the precast erection. “But what is going to end up happening is that, even though the precast garage started later, it will finish much earlier than the [steel framed] police station.
The new parking ramp consists of 332 precast pieces, including 141 double tees (totaling 94,000 square feet), precast concrete columns, beams, spandrels with thin brick, wall panels, a precast stair/elevator tower and a second precast drop-in stair in another corner of the building. It is being built on a poured concrete foundation.
Exterior design elements of the garage consist of thin brick spandrel panels in a “picture frame” layout. The thin brick architectural surface was selected, say Martino, to both match the brick used on the police station and to be in keeping with the downtown Dover Mill aesthetics. The spandrel panels feature modular-size thin brick with 12,000 square feet of MetroBrick #310 Main Street and #350 Main Street Flashed.
The two bay wide, five bay long garage fits in a 121-ft by 212-ft footprint and provides five levels of parking. The ground floor of the garage, built sub-grade with cast-in-place concrete retaining walls on one side of the facility, provides separate on-grade parking reserved for police use. This level contains 35 parking spaces for police and department staff including the department’s three specialty SWAT and crime scene vehicles and provides direct street access at one side of the structure and a speed ramp at another building side. The upper four levels of the garage provide approximately 94,000 square feet of elevated deck, including open-air parking on the top floor, and offer 312 public parking spaces.
General garage access is at the first elevated parking level with ramping along both sides of the structure. Circulation is via interior ramps.
The standard 34-inch deep double tees used for the garage feature 4-inch flange thickness and 30-inch stem depth with a typical span of 60 feet. The thin brick precast spandrels measure 7 feet tall by 60 feet long. A 40% silane sealer and caulking is used on elevated decks and a corrosion inhibitor is used in all horizontal precast components.
Because the garage is so close to the 31,000 square foot police station (a category 4 critical facility), the durability and innate fire resistance of precast was critical, according to Timothy Breen, sales manager with Dailey Precast. Precast wall panels and spandrels with infill panels are utilized where the two buildings abut for fire separation and a fire rated foam is installed along vertical joints of the precast wall panels. Typical column and spandrel framing covers the rest of the garage perimeter.
The project also showcases how precast construction can fit in the tightest of places. The use of precast components requires less staging area at the job site. This was a big advantage since it kept the work site clean and allowed the police station to be constructed at the same time. Precast members were trucked in sequentially as needed.
“Since this is a parking garage,” Martino added, “precast was the most economical way to build, not only from a constructability standpoint but from a speed standpoint. We are erecting a 300-plus space parking garage in about five weeks. This type of structure could not be built in any other way in that time frame.” The garage is also projected to come in on budget.