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More with Less: Code-Compliant OSB Sheathing with Structural Performance Characteristics

Meeting fire codes in zero-lot-line applications, Type III buildings, load-bearing party walls, and roof deck firewalls require fire- resistance ratings, including OSB sheathing that can be specified in these applications.

Developers and builders of zero-lot-line single family homes and Type III (podium) multifamily buildings face a two-fold challenge: what kind of fire-rated sheathing should they specify to meet code that also helps meet the project’s budget and schedule goals?

For architects, that question can be even broader. For example, what exterior wall assembly can they specify to provide more flexibility in designing wall openings, say for larger windows? How can sheathing better support the building’s framing and bracing requirements?

ICC Evaluated Solution

Many code officials are familiar with a proven PS2-rated structural sheathing solution now in service in hundreds of U.S. buildings today. It’s an ICC Evaluation Service evaluated (ESR-1365) exterior wall and roof deck component that’s pre-qualified with:

  • Class A and 30-Minute Flame Spread Rating (ASTM E84, UL 723)
  • 15-Minute Thermal Barrier Protection (UBC-26-2)
  • Combines flame-spread and burn-through resistance
  • CALFIRE/OSFM code approval (CBC Chapter 7A) for use in exterior walls, eaves, and soffits in California WUI Zones

The OSB panel is created by applying a proprietary non-combustible, fiberglass-reinforced Pyrotite® layer to the OSB panel. The product, LP® FlameBlock® Fire-Rated OSB Sheathing manufactured by LP Building Products, blends structural performance with fire resistance in a single panel.

Diverse Application

This combination is a positive development for architects like Michael Cody, AIA, principal of FitzGerald Associates Architects of Chicago. “For certain types of projects, we’re required to meet specific fire resistance ratings in line with building codes. We started using FlameBlock sheathing for its acceptance in the marketplace. People know it. It’s accepted in the building code.”

Cody and other designers are specifying FlameBlock sheathing for a variety of applications, including:

  • Roof decking
  • Bearing and non-bearing exterior walls for Type III construction
  • Load-bearing common walls
  • Load-bearing 1-hour fire-rated exterior walls for Type V construction
  • Exterior walls for zero-lot-line single family homes

Structural Support

The lateral bracing characteristics help architects, owners, developers, and builders think beyond traditional construction methods without sacrificing fire safety and aesthetics. Washington, DC-area multifamily property developer Rick Morris, senior vice president of Avalon Bay, says, “We’re building five and six-story podium buildings. FlameBlock sheathing helps us go high and provide more density.”

Six-Month Exposure

Project Manager Drew Dewey of The Dragas Companies, a Virginia Beach multifamily property developer explains, “When we’ve used fire-rated plywood in the past, it tends to become damaged by water. FlameBlock stays stiff like you expect it to.” An LP official reports that FlameBlock sheathing was recently weather-exposed for more than six months on a Nashville construction project with no adverse effects.

As Morris mentioned, code officials are likely to use FlameBlock sheathing in applications where space and density are critical considerations. Zero-lot-line homes and multifamily developments are immediate beneficiaries. “With Type III construction becoming more and more prevalent, you can expect LP FlameBlock Fire-rated OSB Sheathing to be used more and more. It makes construction easier,” observes Rohit Anand, principal architect at KTGY Group, Inc., in Tysons, Virginia.

Technical Guide Available

Code officials can expect to see FlameBlock panels specified in more podium and zero-lot-line projects not only for ICC-certification and broad rating-agency approval, but also the construction ease Anand refers to.

Code professionals interested in learning more about FlameBlock OSB fire-rated structural panels are advised to click here for a comprehensive 16-page Technical Guide.

The views and opinions expressed in this article are those of the sponsor and do not necessarily reflect those of the International Code Council, or Hanley Wood.

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