Will new seismic codes affect building costs?

The New York City Seismic Building Code, signed into law by Mayor Giuliani on February 22, will affect the way structures am designed, but will not necessarily increase the structural costs significantly.

The new law, under consideration for the past three years, applies only to new construction, including enlargements. Buildings classified in New York City Occupancy Group J-3 (buildings occupied as one-family or two-family dwellings, or as convents or rectories) with not more than three stories in height are exempt. Provisions of the code will affect structures and some non-structural components. For example, facades, walls around vertical exits, and life safety systems will have to be seismically designed; ceilings will not be affected.

The New York City Seismic Code is a revised version of the 1990 Uniform Building Code (UBC), already followed for all federal projects. Cities that enact their own codes usually refine those of the model codes. The UBC code is used in the western region of the U.S., where the incidence of earthquakes is greatest and highest on the Richter scale. The BOCA National Building Code is more prevalent in the Midwest but is now being used in New Jersey and Connecticut. It is not as specific as the UBC code with regard to some non-structural architectural elements and allows the engineer more flexibility in the design of these systems.

The New York City code utilizes a seismic zone factor of 0.15, which establishes the standard for bracing design. The 0.15 factor refers to gravitational acceleration and roughly correlates to 6 on the Richter scale.

Designing a building according to seismic code requires a degree of sophistication, because you can be in compliance with the code and end up with the wrong ductility for your building - resulting in a significantly more expensive structure. The selection of the proper ductility will avoid unnecessary and excessive costs.

Ductility refers to the ability of the structure to perform or deform beyond its elastic limit without failure. There are many ways of achieving efficient structures that will withstand the forces of a severe earthquake. However, engineers and architects have to work together from the start of a new building to achieve a successful and economical seismically designed project.

Construction costs are one of the main concerns for real estate developers. There could be anywhere from zero increase to 5 percent increase in costs, depending on the height of the building, and type of structure foundation, facades, and partitions - and how early the structural engineer collaborates in the design process.

Ysrael A. Seinuk, P.C. followed seismic codes to design several buildings in New York City even before passage of the new regulation. These projects include: the U.S. Courthouse at Foley Square and the Federal Office Building at Foley Square, using the UBC code; and Kings County Hospital Center in Brooklyn and West Queens High School, using the new New York City code.

In complying with the new code, developers should bear in mind the following: (1) the key to controlling costs is working with an experienced seismic engineer; designing for earthquake forces is not the same as designing for wind forces; (2) the type of facade and materials must be carefully evaluated by the engineer, architect and contractor; (3) the soil conditions must be investigated along with the type of foundation required for that soil; and (4) the costs need not necessarily be significantly more if the correct system is selected. A poor selection of structural systems can create inflated costs that are not the fault of the new code requirements.