A fresh old face

August 11, 2010

There comes a time when even the most celebrated building exteriors are in despair. While interior spaces tend to be regularly renovated and upgraded to keep historic buildings functional, the exterior envelope may often be subject to minimal or substandard maintenance, resulting in leaking roofs, crumbling façades and rusting metals details-a face with a frown.

In the past, these ailing structures were often demolished in favor of more modern equivalents. Today, however, preservationists, governments and building teams are pushing-and paying-to restore historic façades to their original grandeur. Many of the projects are initiated by creative entrepreneurs as well as by municipalities interested in urban revitalization.

Philadelphia's City Hall Annex and New York's Tweed Courthouse are examples of projects that involve the careful restoration of entire building envelopes-from roofs and windows to masonry and doors-resulting in faces that once again smile.

Philadelphia's City Hall Annex

Constructed in 1926, the 356,000-sq.-ft. City Hall Annex is located in center-city Philadelphia, adjacent to the famed gothic City Hall building (circa 1871). The 17-story structure-clad in limestone and terra-cotta masonry-served as home for a number of city government agencies until 1987, when it was completely vacated. It would stay uninhabited for a decade.

In 1997, developer Brickstone Realty, Andover, Mass., approached Marriott International Inc. with the idea of converting the annex into a 498-room Courtyard by Marriott hotel, but the building was in dismal shape. The asphalt roof was leaking, the limestone and terra-cotta façades were cracking and the building's prized bronze details were blanketed in patina.

Marriott, known for its adaptive-reuse hotel projects in the center-city area-including the Reading Terminal Headhouse and Girard Trust Bank buildings-agreed to restore the annex at a cost of $67 million.

Brickstone assembled the building team, which included construction manager Gilbane Building Co. of Providence, R.I.; architect Burt Hill Kosar Rittelmann Associates of Butler, Pa., and structural engineer O'Donnell, Naccarato & MacIntosh of Wilmington, Del.

Most of the major work involved renovating the interior, including structural modifications to accommodate a new pool and mechanical room. Restoring the annex's historical exterior-especially the large amount of elegant bronze work-proved challenging as well.

Bronze windows, doors, spandrels and ornamental grilles at the base and top of the building's façades required cleaning, stripping, refinishing and replacement of missing pieces. Gilbane uses a relatively new, environmentally friendly method for cleaning the metal.

"Instead of using a traditional chemical stripper, we sprayed at high pressure a solution made of baking soda followed by water," says Thomas Neider, senior project manager with Gilbane. "It stripped off the patina to the bare metal, which was refinished to a medium-dark finish."

The limestone and terra-cotta exterior was, for the most part, structurally sound, with the exception of a few structural steel members that needed repair. About 50 percent of the joints were repointed, and the façade was cleaned.

While bronze windows adorn the lower and upper-most floors, 1,000 steel windows covered the remainder of the building. All of these existing steel windows were replaced with custom-fabricated aluminum units that replicated the eight different profiles and colors of the originals. The total cost for the window replacement work was approximately $1.7 million.

Finally, the deteriorated roof was replaced with a new EPDM system. "We probably could have repaired the roof, which was about 15 years old," concludes Neider. "But we decided that since the façade was being restored like new, then the roof should have a new face too."

Tweed Courthouse revival

Whereas the exterior of the City Hall Annex building was in rather good structural condition, New York City's Tweed Courthouse was a mess.

Erected over a 20-year period starting in 1861, the ornate five-story marble building was threatened with demolition several times between 1903 and 1974 until it received historic-landmark designation from the New York City Landmarks Preservation Commission.

"Various parts of the building had deteriorated so badly that portions of the property were fenced off and shoring towers erected to stabilize the overhanging projections," says Donald Curtis, senior manager for construction manager Bovis Lend Lease, New York City.

In 1999, the New York City Economic Development Corp. (EDC), on behalf of the city, stepped in to oversee the $80 million restoration and reuse into a museum. EDC commissioned Bovis Lend Lease; architect John G. Waite Associates, Albany, N.Y.; and structural engineer Robert Sillman Associates of New York City to restore the roof, façade, windows and doors. The 30-month project will be completed this December.

Most badly damaged were massive cornice moldings that extend out at roof level from the top of the building's 900-ft. perimeter. Many pieces were fractured and structurally unsafe. Instead of repairing the cornice pieces, the team decided to remove the entire cornice-2.5 million pounds of stone-and replace it with Georgia Cherokee marble, quarried in Tate, Ga.

The new cornice pieces were cut utilizing a computer-driven wire saw, hauled from Georgia in 45,000-pound shipments and installed on the building using a steel-screw anchor system (see "Anchors away: Steel screws support massive stone cornice," left). In all, 4 million pounds of new stone were required to replace the cornice and repair other damaged façade elements, such as projecting window sills, jambs and heads.

In addition, replacement elements are being cut from the old cornice stones and from 115 untouched blocks discovered at the original quarry in Sheffield, Mass.

Other special details, such as stone leaves that once adorned the capitals of the building's columns, are being hand-carved on site.

"These leaves started deteriorating in the 1940s, so the maintenance people chipped them off," says Jack Waite, principal of John G. Waite Associates. "Craftsmen are now carving new leaves, which are pinned and glued into place."

The final price for the stonework will be $16.5 million, Curtis estimates.

Topping off with a new roof

The building team is recreating the original cast-iron roof, with a two-part roof: 24-gauge zinc-coated stainless-steel corrugated panels over EPDM. It was installed on the existing iron trusses, which are structurally sound.

Because the roof could not be worked on in sections, a custom scaffolding system was designed to support a temporary, 75,000-sq.-ft. roof. Recently dismantled, the temporary roof completely covered the building as well as the scaffolding that surrounded the building, guarding the façade work from the weather. Moreover, the scaffolding was engineered to support the weight of replacement stones, which average about 3,500 pounds. "You can literally drive a car around the perimeter of the building on this scaffolding," jokes Curtis.

         
 

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