Both fire-rated OSB and Fire Retardant Treated (FRT) plywood are commonly used in fire-rated wall sheathing and roof deck applications. Because these materials are always evolving, it’s good for architects and builders to know how they compare to each other.
An engineered wood product like LP® FlameBlock® Fire-Rated Sheathing combines a layer of ignition-resistant, cementitious coating with a layer of OSB. It carries an Exposure 1 classification, which means it can withstand normal exposure to moisture during construction. In contrast, some fire-retardant treatments are applied after the plywood is manufactured – and the treatment is sometimes water-soluble, requiring it to be protected from moisture during construction.
A fire-rated OSB product like LP FlameBlock offers both flame-spread resistance and burn-through resistance in the same panel, as verified in tests like the 30-minute Class A Flame Spread Rating (ASTM E84, UL723) and 15-minute Thermal Barrier Protection test (UBC 26-2). FRT plywood has a flame spread rating, but no rating for burn-through resistance.
Fire-rated OSB sheathing has load/span and shear design values that are superior to FRT plywood at the same thickness. In addition, engineered wood sheathing reduces dead load and wall thickness versus FRT plywood. This gives architects more flexibility in designing wall openings, plus more options in framing and bracing to meet structural requirements.
When architects specify fire-rated OSB sheathing, it’s important for builders and subcontractors to “respect the spec” and stick with a material like LP FlameBlock that has so many advantages over FRT plywood.
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The initial conversations with new homebuyers generally focus on architectural style, price per square foot and aesthetic requirements (like the dream kitchen island!). Discussing the structural details that determine the value of your home often happen while poring over blueprints. Here are some tips for having a conversation with your clients to help them understand the importance of investing in the part of their home that’s never seen.
In this guide from LP® SmartSide® Trim & Siding, you’ll learn how to replace rotted siding on a house and how to repair rotted wood siding, depending on the severity of your client’s current siding’s damage. With these simple tips, you’ll be able to spot damage and recommend new products that will help your clients enjoy their home’s new exterior look.
When the build requires greater strength, look for an OSB roof and wall sheathing that is APA Structural I Rated Sheathing—also known as Struc I—for increased structural reliability. What is APA rated sheathing? This valuable designation is a “stamp of approval” that verifies the panels have passed APA’s manufacturing and performance standards.