Webinar Q&A

UL fire resistance directories

Attendee Questions

Understanding the UL Fire Resistance Directories webinar on August 27, 2020

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Why do some fire-rated ceiling assemblies require Type X and others Type C gypsum board?

Type C gypsum board will maintain its material integrity in a fire condition better than Type X gypsum board. The assembly must be constructed with the components listed in the UL design. If the design was tested with Type C gypsum board in the ceiling location, then Type C gypsum board must be installed.

Can UL rated assembly details be copied directly to drawings?

Yes, UL allows the rated assemblies to be placed on drawings exactly as published without any modifications and with credit noted.

Is fire taping required for rated exterior walls using glass mat gypsum sheathing? If so, what product is suggested in an exterior wall application?

Each UL design outlines the required components and acceptable alternatives. The itemized product descriptions indicate if fire taping is required. Reference U305 (bearing wall) Item #2, V438 (nonbearing wall) Item #8 and W469 (bearing wall) Item #9: “Paper tape and joint compound may be omitted when gypsum panels are supplied with a square edge.” All gypsum sheathing products are manufactured with a square edge. Coordinate with the air and water barrier manufacturer to determine their approved taping methods compatible with selected gypsum sheathing product.

Contractors often ask if they can substitute one manufacturer’s gypsum board with another manufacturer’s product. What is the best guidance to provide to the contractors who ask this question?

The contractor must construct the UL fire-rated design according to the products approved and tested per the assembly description. Alternate fire-rated assemblies are typically available from multiple manufacturers with similar components and hourly rating. The contractor should facilitate and submit a UL rated assembly of the same hourly rating and similar components with preferred manufacturer’s products listed.

Can mineral wool be substituted for fiberglass insulation in a rate assembly?

Each UL tested assembly describes acceptable product substitutions and alternates. Review the selected assembly to determine if selected materials are acceptable or search for a similar assembly which lists selected materials. Often in UL tested wall assemblies, the material descriptions state: “Mineral wool or glass fiber batts partially or completely filling the stud cavity.”

What is the difference between restrained and unrestrained systems?

UL publishes an A.E.C. Resources FAQ resource that includes an overview of the difference between restrained and unrestrained systems: “Restrained and Unrestrained are structural conditions. ’Restrained’ pertains to a structural system that takes into account thermal expansion, whereas, ‘Unrestrained’ (more common) does not. UL recommends that you confer with your structural engineer to confirm the system appropriate for your project.” UL also published a blog post titled “Restrained and Unrestrained Assemblies – What Designers and AHJs Need to Know” that provides additional information.

Are maximum wall heights dictated per a given stud size for UL design U465?

UL tested assemblies are minimum requirements and the test chamber is typically 10’ x 10’. Steel stud manufacturers have limiting heights charts that indicate the maximum wall heights based on given design criteria.

Where do you find the list of gypsum core types?

National Gypsum publishes the PURPLE Book. Core types are listed on page 1. The UL website lists acceptable manufacturers and their associated core types in the description explanation of each assembly. GA-605-2018, “Proprietary Gypsum Panel Products for use in UL Classified Systems” is another resource that lists core designations for all gypsum manufacturers.

Can U438 be installed as a rated ceiling in a corridor?

Gold Bond Building Product’s equivalent cavity shaftwall design can be installed as a rated ceiling in a corridor. Refer to the UL Evaluation Report UL ER R3501 for more information and UL design W419.

Do you have a summary list of all UL assemblies for construction like a table of contents?

Yes, UL Product iQ Guide Information for Fire-resistance Ratings has a “Numbering System for Fire-Rated Assemblies” that can be used to find UL assemblies by Types of Protection per specific Groups of Construction. See/scroll to “I. Introduction” in the Guide.

Does green board or gypsum sheathing contain materials that reduce the steam release?

All gypsum board products, regardless of the type, contain chemically combined water that is released as steam in a fire event.

Does the "fire tape" need to be on each side of the wall?

Yes, fire ratings are assemblies - both sides need to be addressed and are taped unless tested differently.

Are there any floor ceiling assemblies that have been tested with full depth insulation?

The assembly component keynotes listed in the tested UL assembly indicate the minimum level of insulation needed. You can add more if it does not exceed the depth of the cavity. Gold Bond Building Products has two assemblies that have unlimited insulation - P533 for roof/ceiling assembly and L588 for floor/ceiling assembly

Is “fire tape” a special type of tape, or are you referring to the general process of applying mud/tape/mud?

“Fire taping” is the name assigned to the process of applying joint compound and tape to joints in fire rated designs. The actual products used are no different than you find in any other part of the gypsum finishing process.

Is it acceptable to use a Level 5 wall finish if the wall is rated with a Level 2 finish?

UL rated designs are tested to a minimum. Any wall that is rated with a Level 2 finish is also acceptable with additional layers of finish.

If you have an assembly (floor, ceiling, wall) and you can't find it listed, what kind of assistance do you provide to find it?

Call 1-800-NATIONAL® for assistance finding an appropriate UL design to meet your requirements. They can also help you with a prescriptive method if no UL-tested assembly is available. You can also use the UL Product iQ assembly tool to help narrow the list of assemblies meeting your selected requirements.

Does UL issue engineering judgments?

No, they do not write engineering judgments. UL typically refers to the product manufacturers in all cases.