The Basics of Fire-Door Assemblies

April 1, 2021
Regulations rule the day when it comes to installing and, possibly, modifying fire doors.

Labeled fire-door assemblies have been available for more than a century in the United States and Canada. Fire-door assemblies are complex systems that feature many individually certified components that, in combination, provide a specified level of passive fire protection. Fire doors are intended to act as closures for openings to limit a fire to a specific compartment, such as a hotel room or classroom, and prevent the fire from spreading through the building.

With that in mind, let’s take a look at fire doors, fire-door hardware, the influence of building codes and the importance of labeling for fire-door assemblies.

Fire-Door Essentials

Fire doors are, most commonly, constructed from wood and steel, but other options, such as fiberglass and fully glazed doors, also exist. A fire-door assembly must include a means of positive latching. Most openings also require the installation of a door-closing device, such as a hydraulic arm-type closer or spring hinges. Other components might include gaskets, seals, door bottoms, glazing, glass light frames and fusible link-equipped louvers. Fire-door assemblies require all components beyond a steel or stainless steel leaf hinge to be listed and labeled, and the lowest rated component of the opening determines the rating for the doorway.

Only products that bear a certification mark are considered as labeled by building codes, and that label is what inspectors look for during an inspection or building survey. For fire doors, the most relevant codes are the International Building Code (IBC), the National Building Code of Canada (for Canada) and NFPA 101. In terms of standards, the installation of fire doors is governed by NFPA 80, Standard for Fire Doors and Other Opening Protectives, while testing is most often conducted in accordance with ANSI/UL 10C, the Standard for Positive Pressure Fire Tests of Door Assemblies for hinged, swinging doors.

Swinging fire doors are provided with fire ratings of 20 minutes, three-quarters of an hour, 1 hour, 1-1/2 hours and 3 hours. The hourly rating replaced earlier systems that featured the letters A through E or various label phrases, such as “fire door for opening in a vertical shaft.” Door hardware, such as bored or mortise locks, fire exit hardware, closers and continuous hinges are rated similarly.

For door hardware, because the labels often aren’t visible after a lock is installed, UL requires companies to stamp a UL Mark and the letter F into the faceplate or other visible surface. Frames might not have a fire rating stamped or marked into the UL Mark depending on the certification mark used by the manufacturer. When no hourly rating is found on the frame, the hourly rating is understood to be up to 1-1/2 hours in drywall or up to 3 hours in masonry construction.

Fire-Door Hardware

Door hardware is a broad term that often encompasses everything but the door leaf and door frame. It might include door-position switches and protection plates. Door hardware for use on fire doors is certified with various ratings and for use on different types of fire doors. When no rating is specified on the product, the product is capable of a 3-hour rating.

If there are limits on product use, the UL Certification entry in UL’s Product iQ Tool will provide information on those limitations. Limitations might be door width, door height, a lower fire rating and whether the product is limited to wood or steel doors. If no limitations exist, the hardware is understood to have a 3-hour rating and can be used on wood or steel doors up to 4 feet in width and 8 feet in height. This concept extends to bored locks, mortise locks, fire exit hardware devices of various types and two- or three-point lock products.

Other commonly certified door hardware installed with fire doors include electronically controlled single-point locks or latches (hotel locks, locks that have card readers or keypads) and what UL terms “auxiliary locks," which consist of deadbolts and electromagnetic locking devices, electric strikes and door hinges. Some products might have multiple certifications from UL, so it’s important to select versions that are certified for fire-door use when installing hardware on a fire-door assembly. If a product must be rated for fire and security, make sure the product is certified for both. One key difference will be in the certification mark used by the manufacturer, because security-tested products feature the word “security” as part of the certification mark.

Fire-rated door hardware might have limited functionality compared with similar products not listed for fire-door use because of the requirements placed on fire-door assemblies. One common example is panic or exit devices. Fire-rated versions appear to be same as nonrated versions, but because of differences in their application, they might have different product features.

UL uses the term “fire exit hardware” for exit devices tested for fire doors in addition to egress considerations, while the term “panic hardware” refers to a device that’s UL-certified only for egress. Products labeled as panic hardware shouldn’t be used on a fire-door assembly.

Why is this important? Panic hardware is permitted by IBC and NFPA 101 to have mechanical dogging or latch hold-back mechanisms, while IBC, NFPA 80 and NFPA 101 don’t permit mechanical dogging on fire exit hardware. To gain equivalent performance, the fire exit hardware device must have electronic latch retraction provided as part of the UL-certified product or as a separately certified accessory installed by following the manufacturer’s provided instructions.

Other similar considerations must be made with electric strikes in fire-door assemblies, because the latch bolts must be held by the strike in case of a fire. Finally, the use of deadbolts and electromagnetic locks always must be reviewed with the building owner and the local authorities to gain their approval, because the locks might limit egress through the doorway or require additional devices to be installed. In any event, manufacturers’ instructions always should be followed during installation.

Working with Fire Doors

Fire doors are regulated tightly through language contained in the IBC and within NFPA 80. Fire-door labeling is expected by these codes and standards to occur only at facilities under an ongoing label and followup program. UL as a certification agency prohibits the application or movement of UL certification marks in the field without UL supervision. Labels for any fire-rated doors, frames or hardware shouldn’t be shipped loose for field application, because this isn’t permitted by UL. 

Because fire doors are in constant use and subject to change, certification agencies and the door or frame manufacturers often receive questions and concerns about modifications, how an opening can maintain its labeled fire rating and what alterations are permissible to an already-rated product. Recent editions of NFPA 80 are uniform in their various clauses under the General Limitations section and, later, the General Requirements section. All of these describe which operations are expected to be performed on a swinging-type fire door under a manufacturer’s inspection service and which operations may be undertaken in the field.

Procedures typically permitted in the field per NFPA 80 include the following:

  • Undercutting wood and composite doors up to three-quarters of an inch (19mm) at the bottom of the door.
  • Adding protection plates.
  • Installing surface-applied door hardware, which is focused on drilling round holes through the face of the door to accommodate through bolts, spindles, etc.
  • Drilling holes for mortise lock trim and spindles.
  • Drilling holes for listed door viewers.

Door preparations that typically have been limited to factory inspection make up a much longer list. These include the machining and reinforcing of doors for locks, hinges, concealed closers, lights and louvers; and the application of laminate faces, cladding and astragals. All of this must be done under the label service of the door manufacturer.

NFPA 80 also requires that fire doors be inspected on an annual basis and provides a checklist that covers how to review a door opening. Care and maintenance as well as methods of repair are discussed in the same section of the document and include parameters for various items, such as ensuring that hardware is fully functional and that no unfilled fastener holes are in the door.

Field-modified options

Modifications occurring in the field and outside a shop or factory further complicate the decision-making process for the manufacturer or testing agency and for the authority having jurisdiction (AHJ) responsible for overseeing the project. Modifications may be permissible, but additional steps are required.

The initial step should be to contact the door or frame manufacturer for their input. The manufacturer often will contact the certification agency for a review of the proposed modification and solicit input. The manufacturer also will provide feedback as to whether the modification will affect the rating of the door assembly as well as the manufacturer’s warranty. This feedback can help to determine the steps that will be necessary to make the modification or repair.

For any field-modification project, the local AHJ should be contacted, so a thorough discussion about the work can occur. The benefit of this early engagement is that all parties involved will know what requirements an AHJ might have for the field-modification work. This conversation also can provide guidelines as to what documentation will be required by the AHJ.

This is an important step, because some jurisdictions won’t permit field labeling to occur and don’t allow changes to be made at a job site. When this happens, it typically results in a replacement of the door or frame, which often ends up being the most cost-effective way to resolve any problems. Discussions with local code authorities might involve more work upfront, but they could prevent unneeded steps and potential problems later.

The labeling agencies also offer various field services for the review of openings, which can provide third-party oversight for projects in the field or an on-site evaluation of the work performed to a door or frame, for the manufacturer, building owner or contractor. These services can include labeling openings where labels are missing by working with the manufacturer of the door or frame or providing an evaluation mark if the product meets established criteria.

Field visits also might be required by the testing agency when the modification is judged to potentially affect the fire rating or the label of the product. These services also might be required by the AHJ if that authority believes that additional oversight is required or if that authority isn’t comfortable accepting the work without additional comment from a testing laboratory.

A fire-door assembly, as noted, is a more complex system than it appears at first glance, but it’s relied upon daily to provide a necessary role. Proper care and maintenance can go a long way to preserve the rating required and provide the level of security desired.

Matthew Schumann serves as the building materials industry manager at UL, which includes fire doors and fire-door hardware. Schumann has been employed by UL for more than 20 years, with areas of expertise in fire doors, glazing products and hardware.