Specifying 1 Hour Fire-Rated Walls

For about a century, architects and builders have used gypsum panels in wall assemblies to meet the criteria for 1 hour fire-rated walls. As product engineering develops, more and more architects are now looking for product solutions that bring added value to their 1 hour fire-rated walls. Many are specifying LP^® FlameBlock^® Fire-Rated OSB Sheathing because it meets code requirements for fire resistant construction while providing faster and easier installation than assemblies that use exterior gypsum and structural panels. They can also provide added design flexibility by reducing wall thickness.

LP FlameBlock sheathing can be used in a few different 1 hour fire-rated wall assemblies, including:

V340: This assembly is commonly used in 1 hour exterior walls along the property line, including single-family construction. This assembly allows for 2x4 wall construction and is fire-rated for 1 hour from both sides. 

Intertek Design LPB/WPPS-60-01: This Intertek-listed assembly is commonly used in 1 hour exterior walls along the property line, including single-family construction. This assembly is fire-rated for 1 hour from both sides. 

UL Design U348: This UL-listed assembly is commonly used in Type V multifamily construction in load-bearing exterior walls. It also allows for the use of fiberglass insulation. This assembly is fire-rated for 1 hour from the interior side only, except when brick and stucco is the exterior facing.

When specified for these 1 hour fire-rated assemblies, LP FlameBlock sheathing reduces wall thickness versus common alternatives that use gypsum and structural panels. It also provides better substrate for securely fastening exterior facing materials. LP FlameBlock sheathing has an Exposure 1 classification-which signifies that panels are intended to resist the effects of moisture on structural performance during active construction. The fire resistance of LP FlameBlock sheathing is not impacted by exposure to moisture during construction.

Fire-rated walls shouldn’t interfere with your design capabilities and construction schedules. Check out our LP FlameBlock page to learn more about the V340, U348 and WPPS-60-01 assemblies.