Understanding the UL Fire Resistance Directory
Attendee questions
Questions and answers from the Understanding the UL Fire Resistance Directory webinars
What is the best resource for finding STC ratings for wall assemblies in UL listings?
Our technical resource guide, The SoundBook®, includes tested assemblies for STC ratings and references UL ratings.
How can I find modifications to tested assemblies on the UL Product iQ site?
The “General Information for Fire-resistance Ratings – ANSI/UL 263 Certified for United States Design Criteria and Allowable Variances” outlines permissible modifications. You can find this information by clicking the first link at the top of any UL design on the UL Product iQ site. Please note you will need to log in to access the site.
Where can I find the requirements or restrictions for attaching equipment or conduit to the face of the fire-rated (GWB) wall, including the type of screws, exposure and spacing of the connectors?
UL does not evaluate anything attached to a fire-rated wall. There is no reason, in our opinion, to expect surface mounted equipment to affect the fire rating.
Can we get a copy of this presentation?
Please contact ngcaia@nationalgypsum.com to receive a PDF version of the presentation. The webinar recording is also available on demand.
In the webinar, it was mentioned that insulation may be added to 1-hour-rated floor-ceiling assemblies provided an extra layer of gypsum board is added to the assembly. How can I determine the required thickness of the gypsum board to add?
According to the “General Information for Fire-resistance Ratings – ANSI/UL 263 Certified for United States Design Criteria and Allowable Variances” Section III, Item 17 found on UL’s Product iQ online certification directory, the additional layer of gypsum board should be of the same type as shown on the individual design. You can find this information by clicking the first link at the top of any UL design on the UL Product iQ site. Please note you will need to log in to access the site.
Is The PURPLE Book® II in addition to The PURPLE Book® I or a replacement?
The PURPLE Book® II is the second edition of The PURPLE Book®.
How can I download copies of The PURPLE Book® and The SoundBook®?
These technical reference guides can be downloaded on National Gypsum’s Design & Resource Center.
Are all your sound-tested designs included in The SoundBook® or are there additional designs that aren’t published there?
National Gypsum’s acoustical testing is ongoing, and we’ve conducted tests since the publication of the book. If your specific assembly is not found in The SoundBook®, please contact your Construction Design Manager for an estimate.
Is it okay to tape and mud over paper that is peeled away from the gypsum core?
Tape is not required to repair gypsum board where the paper has peeled away. We recommend skimming directly over the damaged area with setting type joint compound.
What is the purpose of the hose stream test in the ASTM E119 fire test?
The hose stream test, required for most vertically tested assemblies per ASTM E119, ensures a fire-rated wall assembly can withstand the pressure of water from a hose used to extinguish a fire without being compromised.
Are countersunk screws acceptable? If this poses an issue, what is the solution?
If a fastener is countersunk, then an additional fastener should be added above or below the countersunk fastener. The faulty fastener can remain in place or be removed, and the hole filled with setting type joint compound.
In a G500 assembly, I’ve noticed installers often place a strip of drywall across the top track of a fire partition wall. However, these strips are not always straight, making it difficult for the straight edge of a new sheet to align properly. They usually just tape and mud the gap. Are you okay with this approach?
UL rated G500 series designs do not address the intersection of the ceiling and fire-rated wall. Fire-rated walls should terminate at the underside of an uninterrupted ceiling membrane or continue to the deck above.
Does UL allow for additional layers of gypsum board and the addition of furring channels to a UL fire-rated assembly?
UL allows for additional layers of gypsum board to be added to a fire-rated assembly. However, UL does not have a provision for the addition of furring channels to a fire-rated design. That said, most UL fire-rated designs do include an option for incorporating channels.
Why does the addition of insulation in a horizontal assembly require an extra layer of gypsum board?
Insulation in plenum or joist space of a floor-ceiling assembly can keep heat close to the ceiling during a fire, causing the gypsum board to calcine more quickly.
Is it okay to have a max 1/8" gap at the vertical joints between sheets of gypsum board when the joint lands on a framing member? What about the joints that are not on framing?
All gypsum boards should be in moderate contact with each other.
At what temperature does the gypsum calcination process begin?
The calcination process for gypsum board typically begins at 125 degrees. The gypsum board will not transmit temperatures above 212 degrees until fully calcined.
Given that Type X gypsum board is most often 5/8" thick, is all 5/8" gypsum board considered “Type X”? Or is there also regular 5/8" gypsum board?
Most 5/8" gypsum board is Type X. Some manufacturers, including Gold Bond Building Products, have at least one 5/8" gypsum board product that is not Type X. Gold Bond High Strength Fire-Shield 30 Gypsum Board is Gold Bond's only product that is 5/8" that is not Type X. Type X gypsum board is not always 5/8” thick. This NGC Blog post describes the difference between Type X vs. Type C gypsum board.
Can 15/32" plywood be added to a 1-hour wood stud partition with gypsum wall and keep the original 1-hour rating?
Plywood can be added to any fire-rated wall assembly, per UL’s “General Information for Fire-resistance Ratings – ANSI/UL 263 Certified for United States Design Criteria and Allowable Variances,” Section VI, Item 6. You can find this information by clicking the first link at the top of any UL design on the UL Product iQ site. Please note you will need to log in to access the site.
Does U465 in parenthesis on the presentation slides mean the assembly is both V438 and U465?
Yes, U465 is a UL fire-rated design with multiple gypsum board manufacturers listed. V438 is a proprietary UL fire-rated design with only Gold Bond products listed.
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.
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.”
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 you suggest a 1-HR rated suspended gypsum board assembly, that is not part of a roof-ceiling assembly?
Please refer to UL design I504.
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.
In the front of each section of the UL books were the descriptions of what you could or couldn't swap out, like the screws vs. nails or minimum gauge of studs or concrete vs. CMU etc. Can you still get this type of information on the UL website?
Each UL assembly has a hyperlink to this information. It is a blue hyperlink just below the Design/System/Construction/Assembly Usage Disclaimer - SEE GENERAL INFORMATION FOR FIRE-RESISTANCE RATINGS.
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.