UL Fire-Rated Wall Assemblies: How to Select and Specify the Right One

Select a UL fire-resistance-rated wall assembly by first establishing the wall’s required function and rating under the adopted code. Then locate a current wall or partition design in UL Product iQ, read the complete design together with the applicable BXUV Guide Information, and document every required component and limitation. The design number alone is not a complete specification.

A listed assembly is not a generic recipe that permits any apparently stronger substitution. Framing, membranes, fasteners, insulation, orientation, loading, joints, penetrations, and certified products must match the current listing or an alternative expressly permitted by its Guide Information or accepted through another approved code path.

Start with the code requirement, not a favorite UL number

The 2024 IBC separates two decisions:

1. Other code provisions establish whether the project needs a fire wall, fire barrier, fire partition, smoke barrier, shaft enclosure, exterior wall, or another rated assembly and determine the required rating.
2. IBC §703 establishes how the fire-resistance rating can be demonstrated.

Section 703.2 recognizes assemblies tested in accordance with ASTM E119 or UL 263. Section 703.2.2 also permits specified alternative methods, including designs documented by approved sources, the prescriptive designs in §721, calculations under §722, and engineering analysis based on tested assemblies. Where an assembly complies with neither route, §703.2.3 permits an approved alternative protection method under §104.2.3. A UL design can therefore be an appropriate evidence path, but it is not the IBC’s only path to a fire-resistance rating.

Do not select an hourly rating from a generic building-type table alone. The required rating can depend on the wall’s code function, occupancy relationship, construction type, fire-separation distance, continuity role, shaft or exit use, and applicable exceptions. For mixed occupancies, begin with the IBC fire-separation guide.

Find the current design in UL Product iQ

UL Product iQ is UL Solutions’ certification and product-sourcing database. It supports searches using a design, system, construction, or assembly number as well as company, product, file, and category information. Fire-resistance-rated wall and partition designs are published under the relevant UL certification category; the associated Guide Information explains conditions that apply across designs in that category.

Use this sequence:

1. Record the wall function, required rating, bearing condition, exposure condition, framing material, maximum permitted thickness, and other project constraints.
2. Search Product iQ for candidate wall or partition designs.
3. Open the current design record rather than relying on a manufacturer summary, an old directory PDF, or a design number copied from another project.
4. Read the applicable BXUV Guide Information and the complete design, including notes and optional or alternate items.
5. Confirm that the design is active and that the products proposed in the submittal satisfy each listing item.
6. Save the design identifier, access date, revision or issue information available in the record, and the selected construction options in the project file.

Canadian certifications must not be inferred from a US record. UL identifies assemblies investigated to CAN/ULC-S101 for Canadian code use under BXUV7. Confirm the applicable certification and jurisdiction rather than assuming that a BXUV design and a BXUV7 design are interchangeable.

What does a UL wall design number tell you?

A common shortcut says that U means bearing, V means nonbearing, and W means a specialty wall. UL’s own numbering guidance does not support that shortcut.

UL explains that the initial letter identifies an assembly group and that the first digit further identifies the construction family. For example, U400-, V400-, and W400-series designs have all included metal studs with gypsum board, lath, or plaster. UL has also introduced U4100-series numbers while retaining existing design numbers. The bearing or nonbearing classification must therefore be read from the actual design, not guessed from its first letter.

The number is an identifier, not an encoded specification. It does not by itself establish:

• bearing capacity or structural suitability;
• the permitted stud depth, gauge, and spacing;
• the number, type, orientation, and location of membrane layers;
• whether insulation is required, optional, or restricted;
• permitted exposure direction for a nonsymmetrical assembly;
• the required fastener type, length, and spacing;
• an acoustic rating;
• an approved head-of-wall joint or penetration system; or
• whether a proposed manufacturer’s product is certified for the listed item.

How to read the complete listing

Create a listing-specific checklist instead of reducing the design to “studs plus Type X board.” At minimum, verify:

UL explains that an asterisk beside an item indicates that a UL Certified product bearing the required certification mark must be used. An item without an asterisk is not permission to omit or improvise it; the installed material still has to satisfy that item’s description. UL’s guidance is explicit that the details in the design must be followed.

Are substitutions or “upgrades” allowed?

Do not assume that heavier studs, closer stud spacing, thicker board, additional insulation, a different manufacturer, or another Type X product is automatically permitted. A change that looks conservative for one performance attribute can alter thermal response, restraint, fastener behavior, load, or another part of the tested construction.

A proposed change is supportable only when at least one documented path applies:

• the current design lists the exact product or option;
• the applicable BXUV Guide Information permits the alternative or addition;
• another current listed design covers the proposed construction;
• an approved engineering analysis or other §703.2.2 method substantiates it; or
• the building official accepts an alternative under the adopted code.

Record the path in the submittal. “Equal or better” is not a substitute for listing evidence.

UL 263 and ASTM E119 are both recognized fire-test methods for building assemblies. That does not make different listed designs or products freely interchangeable. The approved design or alternative method still controls the construction that earns the rating.

Coordinate joints and penetrations separately

The wall design does not automatically approve every interface and service opening.

Under the 2024 IBC:

• §714 governs penetrations. Listed penetration firestop systems must be installed in accordance with their tested configuration, listing criteria, and applicable instructions.
• §715 governs fire-resistant joint systems. Section 715.3 recognizes ASTM E1966 or UL 2079 testing, and the joint system must provide the rating required by §715.1.
• Ducts, dampers, opening protectives, structural continuity, and concealed spaces have their own Chapter 7 paths.

UL’s joint-system numbering can help identify the joint family—for example, HW denotes a head-of-wall system—but the joint listing must still be selected for the actual assemblies, movement capability, nominal joint width, materials, and rating. Do not pair a wall design with a remembered HW-D number without checking the current XHBN joint record.

Electrical boxes and other membrane penetrations likewise need their own analysis. UL advises following the wall design and the applicable product-specific classification for boxes, protective materials, and related limitations. A generic putty-pad note is not enough where the proposed condition falls outside the permitted configuration.

Keep fire resistance and sound isolation separate

An hourly fire-resistance rating does not establish an STC rating, and an STC result does not establish fire resistance. Where the IBC Chapter 12 sound-transmission provisions apply to dwelling or sleeping-unit separations, verify the required laboratory or field performance using the applicable test evidence and adopted-code criteria.

Do not publish or specify a single STC value for a UL design unless the cited acoustic test report covers the exact construction being proposed. Stud depth and spacing, cavity absorption, resilient elements, membrane mass, penetrations, flanking paths, and installation quality can all affect sound performance independently of the fire listing.

Specification and submittal checklist

On the drawings and in the specifications

• Identify the required code function and hourly rating.
• Reference the current UL design and the exact selected options; do not cite only a family or prefix.
• Coordinate the partition type, wall sections, reflected ceiling plans, structural details, and finish schedule.
• Identify separately selected joint, penetration, opening-protective, and duct/damper systems.
• State when substitutions require listing evidence, an approved analysis, and design-team/AHJ review.
• Keep acoustic, structural, moisture, impact, and sustainability requirements distinct from the fire listing.

During submittal review

1. Compare every submitted component with the current Product iQ design and Guide Information.
2. Confirm bearing status, framing, membranes, fasteners, insulation, and certified-product requirements.
3. Verify that alternate items are actually permitted by the design rather than inferred.
4. Review wall ends, intersections, deflection heads, perimeter joints, penetrations, openings, and transitions.
5. Confirm that product changes do not break a separate acoustic, structural, envelope, or finish requirement.
6. Resolve deviations through a documented approved path before installation.

What this guide can and cannot determine

This guide explains a repeatable selection and documentation process. It cannot choose a project assembly from a design number alone or verify a proposed substitution without the current design, Guide Information, project details, and adopted jurisdictional requirements. Product iQ and the approved construction documents remain the project-specific evidence.

Primary sources

• UL Product iQ certification and product-sourcing database
• UL fire-resistance products, systems, and designs
• UL steel-stud wall design numbering system
• UL guidance on critical components in fire-resistance-rated designs
• UL AEC fire-rated search resources and FAQs
• UL Canadian fire-resistance certification identification
• UL joint-system numbering guide
• 2024 IBC Chapter 7: Fire and Smoke Protection Features

Technical review record

• Evidence reviewed: UL Product iQ documentation, UL fire-resistance and AEC guidance, UL design/joint numbering guidance, and 2024 IBC §§703, 714, and 715
• Last technical review: August 31, 2026
• Revision: 1
• Jurisdictional scope: US model-code and UL listed-assembly context; local adoption and project approval control

Correction history

• August 31, 2026: Removed an unsupported ten-design/STC table and market-coverage claims; corrected the false U/V/W bearing-status shortcut; replaced the universal substitution/“upgrade” rule with listing- and approval-specific paths; corrected the IBC rating-method, joint, penetration, Canadian-certification, and sound-isolation scope; and added a current Product iQ selection, specification, and submittal workflow.