T his question comes up a lot. The International Building Code (IBC) since its inception has several types of assemblies defined for use in fire-resistance-rated or smoke resistance wall and horizontal assemblies.
When asked about fire resistance from those in the industry, we get all kinds of terms tossed at us. All participating in the construction industry can be guilty of this too. Here are just a few terms that we have heard:
Fire smoke wall—Is this a fire resistance-rated smoke barrier AND fire wall that can have one side of the building collapse and the other standing? Does the wall penetrate each floor with the floor being supported independent of the wall??
Rated partition—Is this a fire partition or smoke partition, fire barrier or smoke barrier? Not sure!!
Smoke wall—Is this a fire wall with smoke resistive properties? A smoke barrier?
Fire Wall—Did the person really mean fire barrier or fire partition?
As can be seen, words have meanings in a big way when it comes to fire resistance. It’s important to call a fire-resistance-rated assembly exactly what it is—otherwise, fire and life safety could be compromised.
This article focuses on fire barriers and smoke barriers. Definitions are critical to understanding—and understanding what’s used for what in building construction. For the purposes of this article, fire resistance-ratings are determined in accordance with the acceptance criteria as published in ASTM E119, Standard Test Methods for Fire Tests of Building Construction and Materials and UL 263 Standard for Fire Tests of Building Construction Materials.
For our discussion, we have been asked to talk about the difference between fire barriers and smoke barriers. However, to grow expertise in fire resistance, it is important to recognize and know all the assemblies—so we all communicate on the same terms.
One point of caution. Fire-resistance-rated walls are built in accordance with the manufacturer’s instructions AND the listing from the UL Product iQ, or another laboratory directory. The assembly has to look just like the listing when it comes to the following:
- Stud manufacturer,
- Type and spacing,
- Fastener type and spacing,
- Gypsum panel manufacturer and type,
- Panel joint location and orientation, and
- Panels installed on one side (some shaft designs) or both sides of the walls.
- Taping joints below and above the drop ceiling is as specified in the listing.
Definitions and Discussion
Below are definitions of assemblies from the 2024 International Building Code—and some discussion about each assembly.
Fire Wall—A fire resistance-rated wall with protected openings, which restricts the spread of fire and extends continuously from the foundation to or through the roof, with sufficient structural stability under fire conditions to allow collapse of construction on either side without collapse of the wall.
This description of a fire wall in IBC’s Definitions and IBC Section 706 shows a very robust assembly. There are fire wall designs that do use gypsum panels. This assembly has very specific details in the listing and manufacturer’s instructions when gypsum panels are used. Concrete and concrete block also have designs that are important to follow.
Fire Barrier—A fire resistance-rated wall assembly of materials designed to restrict the spread of fire in which continuity is maintained.
This fire-barrier assembly is a fire-resistance-rated wall with continuous protection from outside wall to outside wall, horizontal assembly below and above. In section 707.5, walls shall extend through concealed spaces (ceilings, etc.) to the fire-resistance-rated horizontal assembly above, with openings, penetrations, joints and voids protected. Then, in the IBC’s Section 707.5.1, the supporting construction shall have the same or greater fire resistance as the fire barrier it supports.
Fire Partition—A vertical assembly of materials designed to restrict the spread of fire in which openings are protected.
Note the difference in definitions. The fire partition is different than the fire. IBC’s Section 708.4, continuity, exception 2 allows the fire partition to terminate at the next floor/ceiling or roof/ceiling assembly having a fire-resistance rating equal to the fire partition. This is the big difference between the fire barrier and the fire partition. Openings, joints and penetrations are protected.
Smoke Barrier—A continuous membrane, either vertical or horizontal, such as a wall, floor or ceiling assembly, that is designed and constructed to restrict the movement of smoke.
Smoke barriers provide both fire-resistance and smoke-resistive properties. Described in section 709, smoke barriers have a one-hour minimum fire-resistance rating. This one-hour rating is specified in section 709.3. Continuity is important in this assembly, and because it is fire-resistance rated, requires that the assembly extend into concealed spaces penetrations (Section 714), joints (Section 715) and ducts and air transfer openings (Section 717) and have requirements for smoke-resistive properties in their respective sections. Doors (openings) are protected in accordance with Section 716.
For instance, penetrations and joints get L-Rated Firestop Systems. Ducts receive combination fire-smoke dampers. For doors, see section 709.5, as there are exceptions that allow certain door construction.
709.4 Continuity. Smoke barriers shall form an effective membrane continuous from the top of the foundation or floor/ceiling assembly below to the underside of the floor or roof sheathing, deck or slab above, including continuity through concealed spaces, such as those found above suspended ceilings, and interstitial structural and mechanical spaces. The supporting construction shall be protected to afford the required fire-resistance rating of the wall or floor supported in buildings of other than Type IIB, IIIB or VB construction. Smoke-barrier walls used to separate smoke compartments shall comply with Section 709.4.1. Smoke-barrier walls used to enclose areas of refuge in accordance with Section 1009.6.4 or to enclose elevator lobbies in accordance with Section 405.4.3, 3007.6.2, or 3008.6.2 shall comply with Section 709.4.2.
Smoke Partition—A wall assembly that extends from the top of the foundation or floor below to the underside of the floor or roof sheathing, deck or slab above or to the underside of the ceiling above where the ceiling membrane is constructed to limit the transfer of smoke.
Smoke partitions described in IBC’s Section 710 are different than a smoke barrier. As specified, it does not need to have a fire resistance rating. With the lack of fire resistance rating, wall construction is not restricted to the fire-resistance-rated listings. For penetrations, joints and ducts and openings requirements change too—unless required elsewhere in the code. Does that turn the assembly back into a smoke barrier? Good question.
Penetrations and joints do not require L-Rated Firestop Listings, but instead only materials that limit the transfer of smoke. Firestop manufacturers have created smoke and sound sealants for smoke partition applications. Can a L-Rated Firestop System be used? Of course, but the product will not increase the fire resistance rating of the wall from zero hours to one hour by treating with hourly rated penetration, head of wall, perimeter fire containment system and joint systems. The wall assembly should approximate what’s in the listing as well.
For ductwork, a smoke damper isn’t treated the same as a fire damper. The smoke damper might be located away from the smoke partition, with bare duct passing through the wall assembly. Treatment here is again, “limit the transfer of smoke.”
Exterior Wall—A wall, bearing or nonbearing that is used as an enclosing wall for a building, other than a fire wall, and that has a slope of 60 degrees (1.05 rad) or greater with the horizontal plane.
Note that in the IBC’s Section 705, exterior walls might have a fire-resistance rating for various reasons, including building separation distances. Penetrations and joints are not currently required to be treated nor are openings—for now.
Horizontal Assembly—A fire-resistance-rated floor or roof assembly of materials designed to restrict the spread of fire in which continuity is maintained.
What’s amazing is that horizontal assemblies are called various things in the code—floor assembly, roof assembly and ceiling assembly. There is no definition in Chapter 2 for floor-ceiling or roof-ceiling assembly. There is in the UL Fire-Resistance section of Product iQ. There is a definition for roof assembly, but does not include fire-resistance-rated roof assemblies. Note that the horizontal assembly definition includes both assemblies. Again, terminology is important.
Understanding what’s required of a wall assembly—fire-resistance, smoke-resistive properties, or both—dictates how the wall is built. Costs change significantly based on what the wall is named. The fire barrier and smoke barrier need to extend from the horizontal assembly it rests on to the next horizontal assembly above. The smoke partition might not. The fire wall needs to penetrate every floor, terminate 3′ above the roof, penetrating it as well.
With a smoke barrier, the following will change:
- Stud type,
- Spacing,
- Fastener spacing,
- Insulation or not,
- Offset joints from one side of the wall to the other, and
- Joint treatment.
With a smoke barrier or a fire barrier, the following will change:
- The treatment of penetrations,
- Joints,
- Duct and air transfer openings, and
- Openings (doors and fire-rated glazing).
Conclusion
Not all walls are built the same. It’s the definitions that dictate how the walls are built. How a wall assembly is described on plans makes a big difference in cost, performance and function. Code officials, designers and contractors consider using the correct code defined terminology when designing, installing, inspecting and maintaining fire-resistance-rated wall assemblies, so that life safety is delivered when called upon by fire.
Want to learn more? In addition to AWCI membership, consider joining the associations that focus on structural and compartmentation fire-resistance, links below.
Reference
International Building Code (2024) Chapter 7. https://codes.iccsafe.org/content/IBC2024P1/chapter-7-fire-and-smoke-protection-features (accessed August 21, 2024).
Bill McHugh is technical director at the Firestop Contractors International Association (FCIA.org) and National Fireproofing Contractors Association (NFCA-online.org). He was founding executive director at FCIA. He participates at the International Code Council’s Code Development Process, ASTM, UL/ULC Standards Technical Panels, NFPA’s Fire Protection Features Committee. He can be reached at [email protected] and [email protected].
