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Inspiration2 min

How Fire-Rated OSB Outperforms FRT Plywood

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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News & Stories5 min

How to Replace a Piece of Siding

Here is a quick guide to the process of replacing old siding that will lead you to a successful outcome.

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News & Stories7 min
Predictions for 2021 From LP Execs

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Water and Wood: Managing Moisture and Structural Materials

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Oregon Music Garage Part 1: Kyle Stumpenhorst Chooses LP Structural Solutions for Resiliency

Contractor Kyle Stumpenhorst’s latest project in partnership with LP Building Solutions is the Oregon Music Garage in Oregon, Illinois. After successful builds including a shed project, a re-side project and the LP House, Stumpenhorst is at work on this exciting LP Structural Solutions special project: an addition to one of Oregon’s longtime community sites.