Fire-rated assemblies

Frequently asked questions

National Gypsum Construction Services team answers common questions about fire-rated assemblies
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I can access only one side of the wall. How do I achieve a fire rating?

Use UL design W419 for 1- through 4-hour shaftwall systems or UL design V497 for 1- and 2-hour assemblies using Type X gypsum board on one side of minimum 3 ⅝" steel studs.

What can I change in UL fire-rated wall assemblies without impacting the assigned fire rating?

- Stud spacings are maximums, so you can use 16" o.c. on walls tested at 24" o.c.

- Stud dimensions are minimums, so you can always go larger. For example, you can have 6” studs in UL designs that specify 3 ⅝" studs.

- You can add wood structural panels to one side or both sides of fire-rated walls as the base layer or the face layer.

- You can always add more layers of gypsum board to any UL design.

- You can add glass fiber or mineral wool insulation to any UL fire-rated wall assembly.

Is fire taping the base layer necessary in multilayered assemblies?

No, you do not need to use joint treatment materials on base layers of multilayered fire-rated assemblies.

I can access only one side of the wall assembly. How can I upgrade an existing 1-hour, steel-stud partition to 2 hours?

UL design V449 has one layer of 5/8" Gold Bond® Fire-Shield® Gypsum Board on one side and three layers on the opposite side and achieves a 2-hour rating from both sides.

What are some common fire-rated horizontal membranes?

Before the development of fire-rated horizontal membranes, architects used UL fire-rated wall assemblies turned horizontally or shaftwall systems for corridor ceilings. Seeing a need, National Gypsum's 1-800-NATIONAL®Construction Services team developed the horizontal membranes listed below.

A 1-hour horizontal assembly that consists of 3 ⅝" steel studs 16" o.c. with three layers of ⅝" Type X (Gold Bond XP®Fire-Shield®) gypsum board on the underside of the framing. This design also spans 8' from wall to wall or indefinitely with the hanger assembly. It also allows for the use of a premanufactured suspended grid system instead of the steel-stud framing.

This 2-hour horizontal assembly consists of four layers of Type X (Gold Bond XP Fire-Shield) gypsum board fastened to a premanufactured suspended grid system.

This 2-hour horizontal shaft wall assembly includes 4" shaftwall studs with shaftliner panels between each stud and three layers of ⅝" Type C (Gold Bond®eXP®Interior Extreme®Fire-Shield C) gypsum board applied to the underside of the framing. It can span 8' from wall to wall or can be used with the hanger assembly for larger spans.

Learning how to choose UL fire-rated assemblies can be one of the most daunting tasks in architecture. Dive deeper into the topic with our on-demand webinar: Understanding the UL Fire Resistance Directory 101.