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Fire-Resistant Facts

Correctly installed fire-resistant materials and assemblies save lives and buildings

Jensen Hughes Jun18 1

Learn not to burn. This expression has served as the pillar of the National Fire Protection Association (NFPA) for more than 40 years. There’s a lot to learn about fire-resistant building materials and assemblies. When it comes to fire prevention, because they use cold-formed steel, metal buildings have an integral advantage over other building types. Noncombustible steel construction reduces structure flammability and can provide up to a four-hour rating on walls. However, this doesn’t make a building fireproof. High temperatures can still damage metal, especially when it’s unprotected.

To remedy this, correctly installed fire-resistant building materials and assemblies that meet important fire safety standards and codes can stop or slow the spread of fire to provide critical escape time should a fire start. The International Code Council (ICC) and the Metal Building Manufacturer’s Association (MBMA) provide regulations and recommendations for fire resistance that meet the International Building Code (IBC) and local fire codes. Local codes are largely based on tests devised by Underwriters Laboratories (UL), Northbrook, Ill., and the American Society for Testing and Materials (ASTM), Philadelphia.

What is unique about fire prevention in metal buildings? “For metal buildings there may be requirements to provide fire-resistant rated wall assemblies for separating occupancies such as residential or assisted living units, or for means of egress components such as corridors and interior exit stairs,” says Edward Goldhammer, PE, director of codes and standards at Plano, Texas-based Hilti, a designer and manufacturer of technologies and services for the professional construction industry. “Floor and roof assemblies may also be required to be fire-resistance rated depending on the requirements for occupancy separation or the overall type of construction for the building. For example, in the IBC, if the building is built as a Type IIIA construction (noncombustible exterior walls, interior of any material permitted by the code) the floors are required to maintain a one-hour fire resistance rating.”

According to Nestor Iwankiw, PE, SE, Ph.D., senior engineer at the Chicago office of JENSEN HUGHES Inc. (a fire protection and life safety engineering and consulting firm) and a member of the MBMA Fire Protection Counsel, most metal buildings are not required to have fire protection installed on the structural framing. “Since the fire life safety risk in low-rise metal buildings is substantially reduced due to the noncombustible steel framing and much easier means of emergency egress for such conditions, the building code allows the steel structural frames, within certain given height and floor area limits, to be unrated (without any fire resistance rating) as Type IIB construction,” he says. “However, specific walls within this type of building may still be required to be fire-resistance rated because of code requirements for exit corridors, any separation of occupancies or areas, or close proximity to adjacent properties.”

Protection and Balance

For most buildings, both active and passive fire prevention are used. “A balanced design incorporates all three of the essential, complementary fire protection elements: detection, compartmentalization and suppression,” says Richard Rinka, technical manager, standards and industry affairs at the American Architectural Manufacturers Association (AAMA). “In terms of fire resistance, remember redundancy provides safer construction. Additionally, automatic warning and detection systems are a critical factor in limiting fire spread, and loss of life and property. They should always be a part of any fire-protection plan.”

“Depending on a variety of factors—such as size, occupancy, placement on property, location relative to other buildings and others—the building may require a fire-resistance rating for the supporting structure, one or more exterior walls, or the roof,” says David Tomecek, PE, FSFPE, senior fire protection engineer, JENSEN HUGHES, Westminster, Colo. “Automatic sprinkler protection could be required based on floor dimensions, occupancy, building height, type or height of storage and other factors.”

Iwankiw says sprinklers are optional for a typical single-story metal building, but are required for certain types of hazardous occupancies. “However, the code does provide incentives for sprinkler installation through certain allowable increases in building height and area,” he adds. “For these safety and related reasons, some metal buildings will also include sprinklers as additional fire protection.”

Photo courtesy of MBMA

Fire Resistance

Fire-resistant protection can come in many forms: coatings, spray-applied fire-resistant materials (SFRMs), metal track with intumescent tape, and drywall on both sides. It can include flute covers and/or mineral wool. Goldhammer contends for metal buildings, common applications for fire-resistant protection include penetrations through rated assemblies and continuity head of wall joint system between a fire barrier wall and non-rated metal deck roof or floor system. “If the structure is very large or involves high-piled storage, smoke and heat vents could be required, as well,” says Sean Donohue, PE, director of JENSEN HUGHES’ Colorado Springs, Colo., office. “This may involve spring-loaded roof vents or a mechanical system. Additionally, fire detection, additional doors for egress, hose systems for firefighting, emergency alarms, non-water-based fire suppression/extinguishing systems (gaseous or chemical) and a plethora of other fire-protection features can become necessary depending on similar factors described above, the owner’s own decisions regarding protection and insurance agency input.”

Iwankiw says gypsum board, when required, is and has long been, the preferred product of choice for passive fire protection of fire-resistance rated walls, columns or roofs of low-rise metal buildings. “The reasons for this are that gypsum board can function both as a fire protection cover and an attractive interior finish, its availability at competitive prices, lightweight and the installation is relatively clean and efficient,” he says. “Steel stud framed walls with gypsum board, and board box-out enclosures of steel columns and ceiling membranes are commonly used. A negative is that gypsum board needs supplementary framing and attachment to form a member enclosure or protective membrane.”

Encasing a metal building’s structural members in gypsum, mineral board or similar materials must be done once the structure has been raised and the exterior walls put in place so that connections and joints can be properly protected. “The same is true of SFRMs,” Tomacek says. “Fire-resistant coatings (intumescent coatings and mastics) can often be applied prior to steel erection, but touch-ups will be necessary to ensure complete coverage to the required thickness. Exterior fire barrier walls and roofs will, of course, need to be installed once the steel is erected, but prior to other construction. Access to the supporting steel and cross-members is typically important for the listed and/or approved systems used with steel buildings.”

Install as Tested

To save lives, assets and the building itself, fire-resistant materials and assemblies must be installed as tested. Two common installation issues here for both metal and nonmetal buildings are structural design coordination and installation timing. The design team must determine very early on whether fire protection features will be included in the building and where those loads must be carried. On a recent Jensen Hughes project, a fire pump was successfully avoided, but it caused the upsizing of some fire protection pipe from 4 inches and smaller to 6 inches and 8 inches. Donohue says this placed a different load on the building than was originally planned. “Additionally, there may be a need to achieve specific spacings or sizes of roof members to allow for hanger placement on sprinkler systems, for efforts regarding fireproofing engineering judgments because of unique column/ beam shapes or thicknesses and/or particular framing arrangements for smoke and heat vents,” he adds. “Those elements will need to be included in the building specifications from the design team to the metal building manufacturer.”

Installation timing is important because fire-resistance rated assemblies often require access to portions of the structure that will be enclosed or hidden as construction progresses, making it impossible to complete the fire-resistance rated assembly properly. Similarly, placement of structural members and enclosing of walls and roof must be accomplished before installation of the fire sprinkler system begins, since measurements from those elements are critical. “Regarding sprinkler protection, assessing the need for a fire pump, as alluded to above, can have a significant negative effect on the project if it is not addressed,” Donohue says. “One should never assume that they do or don’t need a fire pump; reach out to a sprinkler contractor or fire protection engineer and conduct the necessary hydraulic calculations early on in the process. [Also] C- and Z-shaped purlins often appear to be great for installing sprinkler piping supports. However, there are a limited number of connectors that are approved by the various fire-protection standards and approval agencies, and many place point loads on the purlins or puncture the purlin in ways that compromise its structural ability. Obviously, coordinating the two is more important than they might seem.”

Photo courtesy of MBMA

Common Mistakes

Goldhammer cites the following frequently made firestopping installation mistakes:

1. Not selecting the proper firestop system for the application. Often the actual installation does not match the listing requirements (example: wrong penetrant type, wrong joint width).

2. Not following the requirements of a listed and tested system. For example, using materials from multiple manufactures or using materials such as tape or drywall mud not part of the tested system.

3. Job-site conditions create a need for an engineering judgment. Although there are thousands of tested and listed systems, the job-site condition may not exactly meet the stated range of a tested system. Therefore, an engineering judgment is provided by the manufacturer, which is not listed but is expected to pass if tested. These engineering judgments may also require a professional engineer stamp. Always consult the project design team when job-site conditions do not match tested solutions.

4. Not properly cleaning the substrate prior to installation of the materials which can lead to adhesion issues.

5. Incorrect annular space for through penetrations. The annular space is the distance between the penetrant and nearest inside edge of the opening. At times the installation exceeds the limitations of the annular space requirements. This can also include conditions where the penetrant comes in contact with edge of opening. There are tested solutions with both point of contact or continuous contact.

6. Insufficient depth of fill material. Tested and listed systems will provide a minimum depth of a particular product which is the depth that passed the test. Installing less than the minimum depth could result in the system failing prematurely.

7. Improper backing materials. Backing materials are allowed in accordance with the requirements of the listed system.

8. Improper mineral wool installation within joint system. Mineral wool is commonly used to stuff the joint which is then sealed at one or both faces of the wall or floor with an elastomeric material. Tested systems require a specific density and compression for mineral wool. This is sometimes overlooked and could result in premature failure of the joint system.

Completeness and Continuity

Iwankiw stresses that completeness and continuity are major code requirements for any rated assembly. He stresses continuity means not only that all the fire protection components are properly provided and installed, but that there are no breaches or openings in the assembly. “These characteristics enable the assembly to serve either as a fire barrier that will prevent the propagation of fire and smoke beyond the fire’s originating source and/or to delay the heating effects of a fire on structural members as an insulating enclosure or membrane,” he adds.

Fire-resistance rated assemblies do not have a lot of flexibility due to the manner in which they are tested and/or approved. And because steel element dimensions change over the height/length and the fire-rated assemblies are dependent on the size ratios of the element, engineered steel elements can be problematic to work with. “Connection points needs to be addressed, too, and metal buildings tend to be the most progressive in using new methods that haven’t been necessarily addressed by fire testing,” Tomecek says. “Fire-resistance rated metal panel walls and ceilings that are often specified by the design team can be found in fire-resistance rated models, but often only in a limited range of hourly rating, wind or penetration ratings and so forth. Additionally, such panels have limited number of penetration details, often for smaller sizes of pipes and duct work. Therefore, details need to be developed early on for items such as cable trays, bus ducts, larger pipes, larger ducts, conveyors or other items that might be installed.”