Hearst building design grounded in lath and plaster.

Hearst Corp.'s new 46-story headquarters at 57th Street and Eighth Avenue may not be the first skyscraper to be constructed around an existing building, but it certainly is a clever approach to a recurring situation in crowded urban areas.

The existing art-deco building had been awarded landmark status in 1988. So its facade had to be preserved--never mind that Hearst had erected the six-story structure in 1928 as home base for its magazines.

Since Hearst was required to protect the exterior of its old building, the company decided to gut it and transform the interior into a spectacular and lofty lobby.

Beyond the familiar entrance arch on Eight Avenue is a three-story-high, $8 million "Icefall," with water cascading down an immense stepping sculpture that's bisected by escalators.

Above the atrium's third floor are large balconies that serve various functions. One is a cafeteria. Employees lunching there can gaze up, through the skylight that now crowns the shell of the old building, and see their distinctive new tower. It was designed by Foster& Partners, an architectural form based in London.

So its no surprise that Foster & Partners wanted harmony between the interior and exterior of the lobby. To provide the best complement to the old building's limestone-block facade, time-honored lath and plaster was the first choice.

Trying to paint drywall to match the masonry exterior was unlikely to yield satisfactory results. Hearst agreed.

"Classic lath and plaster was selected for the interior walls not only for esthetics and mold resistance but also because it's more durable than sheetrock and has a better fire rating," said John Coffey, president of Metallic Lath & Reinforcing Ironworkers Local 46 in New York. His union members installed the metal lath and plaster last summer, covering all three walls surrounding the Icefall, floor to skylight, in just eight weeks.

"Lath and plaster offers outstanding fire resistance," according to Robert Ledwith, president of the New York Lath & Plaster Institute.

"A typical lath-and-plaster wall provides twice the fire resistance of sheetrock walls typical in New York apartments and offices. Ask any New York firefighter which material they prefer, and its will be lath and plaster every time."

"That was a really tight schedule," notes Coffey, "because we applied the optimum three Separate coats of plaster--plus, our workers had to mix the final coat to match the color of the outside limestone."

Three-coat plaster jobs start with a base coat formulated to grab onto the lath. That's followed by a brown coat (it contains extra sand) to provide bulk and strength, which gets topped off with the finish coat. All 35,000 s/f of plaster in the lobby is "a total of three-quarters of a inch thick," Coffey added. "It's going to last practically forever."

Coffey admired the look of the plaster surface as designed by Foster & Partners. The normal expansion beads create a pattern like that of the exterior limestone blocks. The main purpose of the beads, of course, is to give the plaster room to expand and contract without cracking. Durability was clearly a design priority throughout, particularly in terms of fire protection and worker safety, because of the terrorist threat to innovative buildings like the Hearst tower.

Foster & Partners placed the structural core off-center, farther to the west--the only side facing a street and possible car bombs. All windows in the existing building were replaced, using blast-resistant glass. The emergency stairwells are encased in concrete blocks and the stairs are wider than required by the building code to speed evacuation in case of a fire.

The skyscraper's unique diagonal-grid frame, which starts above the old building, stems from the off-center core's need for unusually robust support. WSP Cantor Seinuk Group, the project's structural engineer, analyzed several alternatives before homing in on the distinctive "diagrid" system. Compared to a conventional perimeter frame, the diagrid design reduced steel consumption by roughly 2,000 tons, or 16%. "Foster & Partners and WSP Cantor are pioneers in recognizing that better building safety can no longer be an option," said Coffey.

"We need more architects and engineers like them. We need all creative professionals to get involved in developing safer office towers. We have to return New York City to its historical position of leadership on issues of building safety."