Business Advice4 min


Fire-rated sheathing, such as LP® FlameBlock® Fire-Rated Sheathing, has been proven to slow the spread of flames when installed according to appropriate code requirements. However, details in the installation process can trip up even the most seasoned professionals—and mistakes can compromise the build’s fire-resistance capabilities.

When it comes to how to install fire-rated OSB sheathing, ensuring the soffit and eave details are aligned with code requirements can be a challenge. Here, we’ll take a look at two methods that can help you install this part of your wall assembly accurately and in line with codes for fire resistance. As always, check your area’s specific requirements for any further details.

Why Soffit and Eaves Make a Difference in Fire-Rated Sheathing Installation

First of all, why do soffit and eave installation practices make a difference when it comes to fire resistance? Heat can be trapped in these overhangs, offering more chances for a structure to ignite. Then, if they do ignite, a quick connection to the rest of the home through the roof and attic is enabled. For this reason, ensuring a structure meets code requirements for fire resistance is key, especially since codes do not only address wall and roof assemblies but also the parts of a building connected to the walls, such as soffit and eaves. 

Often, for areas in which fire resistance is a major concern, eliminating overhangs altogether or making them as short as possible is best. However, sometimes this is not possible, since soffit and eaves are also needed for moisture control. If your build includes them, code-approved soffit and eave detail is critical. 

Fire-Rated Sheathing Tips for Installation

The installation of fire-rated sheathing on exterior walls begins with a few best practices. Here are a few basic tips to get started on your LP FlameBlock sheathing installation:

  • Store panels in a clean, dry area off the ground. If possible, store indoors. If outside, cover with plastic sheets, tarps or the packaging cover.
  • For roof installation, place the Pyrotite® coated side of LP FlameBlock one-sided panels facing down.
  • For wall installation, install in accordance with the specified fire-rated assembly. In the absence of a listed assembly, install panels vertically with the horizontal joints blocked.
  • Drive nails 3/8-inch from panel edges, 6 inches on center along supported panel edges and 12 inches on center at intermediate supports, unless otherwise specified. 

Installation Detail Method #1 

LP FlameBlock sheathing is versatile enough to be used in most types of construction and is a listed component in many fire-resistant rated wall assemblies by UL and Intertek. One method of achieving code compliance with soffit and eave details is by installing a solid block of dimensional lumber that spans from the top plate to the underside of the roof deck. This method can be used per the 2018 International Residential Code (IRC).

Remember, when LP FlameBlock panels are installed as roof deck with open eaves, the exposed underside of the panels, as well as any exposed edges, must be coated with exterior-grade paint. 

Installation Detail Method #2 

Another method for meeting code with LP FlameBlock sheathing is to install solid dimensional blocking on the fascia and soffit. This should be completed as a first step prior to finishing materials. This method, in addition to the previous one, provides the same durable fire-rated protection with slight distinctions in how they’re built. 

When an LP FlameBlock wall assembly is used in conjunction with one of these methods, you can achieve a system that conforms to code requirements for fire-resistant construction.

Prevent Fire-Rated Sheathing Installation Mistakes With Proper Soffit & Eave Installation

The correct installation of fire-rated OSB sheathing on exterior walls is crucial, especially with strict code requirements for builds in areas where fire resistance is a top concern. Be sure to study the specified fire-rated assembly before beginning and refer back to the LP FlameBlock installation instructions for complete details.

Check out several examples of approved wall assemblies that include LP FlameBlock sheathing and add strength and fire resistance to your build without sacrificing design flexibility.

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