Report: Fire Ratings for "L-Type" Intersections in Walls

Originally published by the following source: SBC MagazineSeptember 17, 2018
by Kevin Kutschenreuter, Sean Shields and Kirk Grundahl, P.E.


SBCA is pleased to announce the publication of SBCA Research Report 1304-03: Use of “L” Type Partition Intersections in Fire-Rated Assemblies. This report provides best practice documentation to share with specifiers, the fire service and building officials who need help with fire-resistance techniques for L-type wall assembly connections on your jobsite.

Figure 1: U-shaped partition intersection as shown in UL538

Figure 2: L-shaped partition Intersection replacing U-shaped in identical wall assembly to that specified in UL538

Many builders use an L-type partition intersection in wall construction, as it offers a number of potential benefits compared to U-shaped connections. One of these benefits is a reduction of lumber. Since the L-shaped design requires one less stud per intersection, using them for a building that has potentially hundreds of these types of intersections can mean considerable savings in lumber costs.

In addition, the elimination of the extra stud makes insulating easier. Since U-shaped intersections require that insulation be added during installation, doing so can often be overlooked or neglected, leading to the creation of a cold spot. L-shaped partitions, on the other hand, create easy access and space for insulation to be added after installation, reducing hassle and are a better building envelope best practice.

Despite these benefits, a question is sometimes raised with respect to the fire-resistance code-compliance of “L”-shaped connections. While neither the IBC® nor IRC® specifies what attachment type must be used, a  fire-tested partition connection listed in the UL Fire Resistance Directory (Design Number L538) includes a U-shaped connection.

 SBCA’s new research report demonstrates that replacing a U intersection with an L intersection does not reduce the fire performance rating detailed in UL538.  Providing ample code references and technical detail, the report concludes that, per IBC 104.11, L-type partition connections are a suitable alternative for walls constructed in accordance with applicable codes.

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