Study Totals Hollow Core, Masonry Economy In Fire-Safe Design

A Fire Safe Construction Advisory Council (FSCAC) report concludes that a compartmentalized construction approach using concrete-based methods is competitive

A Fire Safe Construction Advisory Council (FSCAC) report concludes that a compartmentalized construction approach using concrete-based methods is competitive with alternative methods that typically combine combustible materials and active fire suppression. The council retained an independent engineering firm to conduct a cost-comparison study among five building systems. Engineers confirmed that balanced design using concrete and masonry construction saves lives and protects property from building fires, while offering an economical building system.

FSCAC is a consortium of the Northeast Cement Shippers Association and the precast or masonryproducer-backed NE/NY Fire Safety Construction Advisory Council, Pennsylvania Fire Safe Construction Advisory Council, and Mid-Atlantic Fire Safety Construction Council. The balanced design method espoused by council members encourages the incorporation of detection (alarms), suppression (automatic fire sprinklers) and containment (noncombustible wall and floor assemblies) into a building, along with education of occupants and emergency responders in the event of fire.

Explains Precast/Prestressed Concrete Institute President James Toscas, Because International Building Code allows larger buildings to be constructed from wood when they incorporate active fire-protection systems Û such as sprinklers Û designers assume that wood provides a more economical approach than using passive fire-resistance construction techniques, such as compartmentalization and specification of fireproof materials. Lacking reliable documentation to support or refute this perception, FSCAC members decided to study design options in detail. Accordingly, prototype buildings in three Mid-Atlantic locations (to allow for prevailing wage rates and regional variations) were evaluated, yielding evidence that compartmentalized construction using concrete-based methods adds no appreciable expense.

Data regarding real and perceived costs of competing building systems was obtained by a State College, Pa.-based team comprising Haas Architects and Engineers; Tim Knisely, a senior fire and commercial housing inspector for the Centre Region Code Administration; and, Poole Anderson Construction, which supplied cost estimates. To more realistically address the variety of construction configurations commonly found in the multifamily dwelling marketplace, the report affirms, a multifamily residential plan was selected consisting of four-stories, 25,000 sq. ft. per floor, and two interior layouts: a one-bedroom and a mixed-bedroom design.

The report thus evaluated the impact of building a fire-resistant multifamily residential structure using the following five building techniques to meet 2003 IBC requirements:

  • Conventional wood framing with a wood floor system using Type 5A or 5B construction;

  • Light-gauge steel framing with a cast-in-place concrete floor system on a metal form deck;

  • Load-bearing concrete masonry construction with a precast concrete plank floor system or a cast-in-place concrete floor system;

  • Precast concrete walls with a precast concrete floor system;

  • Insulated concrete form (ICF) walls or interior bearing walls made with concrete masonry units (CMU) with a precast concrete plank floor system or a cast-in-place concrete floor system.

On the basis of projects sited in Framingham, Mass.; Harrisburg, Pa.; and, Towson, Md., the study concluded that using a compartmentalized construction method incorporating precast required less than 2 percent more total construction cost. Comparatively speaking, this is less than the contingency budget typically recommended for unanticipated expenditures during the project, the report asserts.

Moreover, Toscas emphasizes, the standardized design used in the study could not fully leverage the advantages offered by a total-precast solution. The cost evaluation also did not take into account substantial savings due to precast’s longer spans and shorter construction schedule that might entirely eliminate the cost differential in the overall budget.

The report maintains, however, that using concrete materials can provide additional long-term benefits. The minimal increase in construction cost can help pay for itself over the life of the structure, it states. Materials like concrete masonry, precast and cast-in-place concrete have many advantages beyond fire performance, including resistance to mold and to damage caused by water in the event of a fire. In many cases, with this type of construction, the damage outside the fire compartment is minimal, the study confirms. This provides for reduced cleanup costs and quicker reoccupation of the structure.

The council’s 800-page report is available through PCI’s Northeast regional marketing office. Û