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Q&A: Wood and Steel Joists for use in horizontal UL Fire Resistance Designs

There are many UL fire resistance designs featuring the use of wood or steel trusses and joists. These assemblies provide many options for building a horizontal assembly and determining if a joist or truss is appropriate for a specified use can be challenging.

September 11, 2020

Question:

How can I determine if a joist or truss is appropriate for use in the UL fire resistance design I have selected?

Answer:  

The first step is to look for the UL Certification on the individual truss or joist. Only those products bearing the appropriate UL Certification Marking and the company’s name, trade name, trademark or other recognized identification should be considered covered by UL’s Certification and Follow-Up Service Program. When the structural element is required to bear a UL Certification Mark, an asterisk (“*”) is provided by UL in the recognized design. This asterisk is then followed by the manufacturer of the truss or joist and the product’s nomenclature in the design. When a UL Certified truss or joist is specified, the truss or joist must bear the UL Certification Mark for the assembly to achieve the hourly rating and load rating specified in the design. If the UL Certification Mark is not present on the truss or joist, there is no assurance that the truss or joist has been subject to the UL Follow-up Service program or is representative of the materials originally submitted to UL for testing and certification. 

The next step is to begin a thorough review of the specified UL fire resistance design. UL Product iQTM can be consulted as the source of the most up-to-date certification information published by UL. Product iQ™  is free to use, but does require a one-time registration. Each published UL fire resistance design featuring a truss or joist includes a full description of the truss or joist permitted for use in the assembly. The description will also include the method of fastening, orientation, bridging options and any other installation considerations that must be followed during construction. Substitutions of trusses or joints from other manufacturers or use of other models not specified in the specific UL recognized fire resistance designs have not been investigated by UL.

To provide some clarity on the truss and joists, UL Certified trusses and joists are evaluated in accordance with UL 263, Fire Tests of Building Constructions and Materials, as part of a complete fire resistive assembly. These products are included in various UL issued G, H, K, L, M, N and P fire resistive designs. See the category BXUV guide information for more details. UL currently certifies both wood and steel structural elements for use in these UL issued fire resistance designs. The steel elements will be certified by UL as structural steel members in UL product category CJFS while the wood elements will be certified by UL as structural wood members in UL product category CJIX. In addition to the noted fire resistance designs, wood and steel structural elements will have individual entries published in Product iQ. The Product iQ entries contain a list of products certified by UL and the correlating UL fire resistance designs where those products may be used. Product iQ can then be used to confirm published certification for the product to be used.

In closing, there are many UL fire resistance designs featuring the use of wood or steel trusses and joists. These assemblies provide many options for building a horizontal assembly with an hourly fire rating while maintaining a certain load rating for the floor. For these assemblies to maintain the hourly and load ratings indicated in the header of each design, the assembly must be constructed as described in the published UL fire resistance design and each individual truss or joist must bear the UL Certification Mark as a structural wood member or structural steel member. 

Q&A: UL Critical Component Identification in Fire Resistance-rated Designs

Have you ever wondered why some items within UL Certification designs have asterisks following an item’s description? In this Q&A, we’ll explain what their meaning is.

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