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Firestopping for Concrete Masonry Walls

  • August 2018

INTRODUCTION

Concrete masonry is widely specified for fire walls and fire barriers because it is noncombustible, durable and economical. Although these constructions are ideally continuous, various conditions require joints or penetrations in fire walls and fire and/or smoke barriers, including movement joints, pipe or cable penetrations and electrical wiring and outlets. Regardless of the type of penetrating item, gap or joint, the International Building Code (IBC) (ref. 1) requires that the continuity of the fire-resistant or smoke-resistant assembly be maintained.

A through-penetration firestop system is an assemblage of specific materials or products designed, tested and rated to resist fire spread for a prescribed period of time through openings made in fire resistance-rated walls, floor/ceiling or roof/ceiling assemblies. Firestopping must be installed in accordance with code requirements to maintain fire and life safety.

Choosing an appropriate firestopping system is a key component to a successful installation. The firestop system must be chosen from a building-official-approved listing service. Alternatively, one of the generic listed materials—concrete, mortar or grout—can be used within the limitations of the code.

Various methods are used to maintain continuity where joints, gaps and penetrations exist in fire-resistance-rated masonry construction. For details of control joints for fire-rated concrete masonry construction, refer to the subsequent Joints section and TEK 07-01D, Fire Resistance Ratings of Concrete Masonry Assemblies (ref. 2). Note that materials installed in joints must resist environmental and movement characteristics as specified by the design professional.

MAINTAINING THE CONTINUITY OF THROUGH-PENETRATIONS

The IBC allows several options for extending the fire resistance rating to protect penetrations through fire walls, fire barriers, smoke barrier walls and fire partitions. Section 713.3 of the 2009 IBC (Section 712.3 the 2006 IBC) contains explicit options permitting the use of concrete, mortar or grout to extend the fire rating through the annular space between the penetrating item and the concrete masonry wall provided the following conditions are met (see also Figure 1):

  • the penetrating item(s) must consist of steel, ferrous, or copper pipes, tubes, or conduits;
  • the nominal diameter of the penetrating item(s) cannot exceed 6 in. (152 mm);
  • the opening through the wall cannot exceed 144 in.2 (0.0929 m2); and
  • the concrete, mortar or grout is permitted where it is installed to the full thickness of the wall or the thickness required to maintain the wall’s fire resistance rating (see TEK 07-01D (ref. 2) for concrete thicknesses required to meet various fire resistance ratings). Note that placement around a penetration with masonry usually requires cutting of units. In the case of rectangular penetrations, continuity can be easily maintained by laying units with the uncut web adjacent to the penetrating item and filling the annular space with mortar

In cases where the penetrating item is contained in a sleeve, the annular space includes the space between the penetrating item and the sleeve as well as the space between the sleeve and wall assembly. Although the mason contractor is responsible for mortaring in the sleeve, filling the annular space between the pipe and the sleeve after the pipe is installed is the responsibility of the firestop contractor, piping contractor, or other firm assigned by the prime contractor or building owner/manager.

The design professional is responsible for assigning fire resistance ratings and smoke resistant assemblies, and specifying the test methods for maintaining continuity of the wall, when required. The mason contractor is not responsible for applying firestop material other than mortar, grout or concrete. The mason simply follows the plan sheet for initial construction by laying up the wall around the penetration, or if appropriate, cutting into a constructed wall. When the limitations for using mortar, grout or concrete indicated above are exceeded, then the firestop contractor, piping contractor or other designated party must apply the appropriate firestop.

If one or more of the above conditions for using mortar, grout or concrete are not met, then the firestop system must be tested in accordance with ASTM E814, Standard Test Method for Fire Tests of Penetration Firestop Systems (ref. 3), UL 1479 Fire Tests of Through Penetration Firestops (ref. 4) (with a minimum positive pressure differential of 0.01 in. (2.49 Pa) of water), or an approved assembly tested in accordance with ASTM E119, Standard Test Methods for Fire Tests of Building Construction and Materials (ref. 5) or a building official-approved alternative per Chapter 1 of the IBC.

ASTM E814 and UL 1479 were developed specifically for through penetrations and cover membrane penetrations as well (see next section, Protecting Membrane Penetrations). Both of these test methods use similar time/temperature curves, and result in a flame rating (F) for the firestop system. The F rating indicates the number of hours the firestop system resisted the passage of fire (during the fire exposure test) or water (during the hose stream test), whichever is lower. The F rating must meet or exceed the required fire resistance rating of the assembly being penetrated.

In addition to the F rating, there are also T (temperature) ratings, L (air, simulating smoke) ratings and, if water resistance is required, W ratings. The T rating indicates the length of time (in hours) it took for the firestop system to heat up on the non-fire exposed side of the assembly to the point where it could cause ignition of combustibles on the unexposed side. This is considered to occur when the temperature on the non-fire-exposed side of the firestop system rises to 325o F (162o C) above the ambient temperature.

It should be noted that in order for a firestop system to obtain a T rating, it must first obtain an F rating. F ratings are required for all firestop systems (except when concrete, mortar or grout are used under the conditions described above), whereas T ratings are not always required.

The L rating is used to maintain the continuity of smoke barriers. UL 1479 is currently the only standard that measures the passage of air through the assembly including the penetrating item, at ambient and at 400o F (204o C). The ambient temperature condition simulates cold smoke, while the 400o F (204o C) condition simulates hot smoke, both measured in cubic feet per minute per square foot of opening area. The lowest L rating is <1 cfm/ft2 (0.005 m3 /s-m2 ). For a penetration assembly in a smoke barrier, the 2006 IBC allows air leakage of 5 cfm/ft2 (0.025 m3 /s-m2 ) of penetration opening at 0.3 in. of water (7.47 Pa) for both the ambient and elevated temperature tests.

PROTECTING MEMBRANE PENETRATIONS

Membrane penetrations, addressed in IBC (2009)section 713.4.1.2, are those which penetrate only a portion of the wall assembly, such as the opening for an electrical outlet. The IBC language for protecting membrane penetrations is very similar to that for through penetrations. However, there are specific prescriptive criteria that address electrical boxes no larger than 16 in.2 (0.0103 m2) in fire walls with a fire resistance rating up to two hours. These criteria address the maximum area of openings, the annular space between the wall and the box, and separation or protection of such boxes when installed on opposite sides of the wall (see Figure 2).

DUCTS

Ducts are addressed in IBC (2009) section 716. Non-dampered ducts that penetrate fire rated walls must comply with the requirements for through penetrations, as described above. Dampered ducts and air transfer openings are tested to either UL 555, Standard for Fire Dampers (ref. 6) or UL 555S, Standard for Smoke Dampers (ref. 7), or both for fire/smoke dampers. Fire and smoke dampers must be tested according to the standards listed above; there are no prescriptive damper treatments that are deemed-to-comply with the IBC.

JOINTS

In Section 714 of the 2009 IBC, any joint in or between fire resistance-rated walls, floor, or floor/ceiling assemblies and roofs or roof/ceiling assemblies is required to provide a fire resistance rating at least equal to that of the wall, floor or roof in or between which it is installed.

The void created at the intersection of an exterior curtain wall assembly and the floor or ceiling assembly must be protected in accordance with IBC Section 714.4.

Fire resistant joint systems must be tested in accordance with the requirements of either ASTM E1966, Standard Test Method for Fire Resistive Joint Systems (ref. 8), or UL 2079, Standard for Tests for Fire Resistance of Building Joint Systems (ref. 9). Control joints not exceeding a maximum width of 0.625 in. (15.9 mm) can be installed if tested to ASTM E119 or UL 263, Standard for Fire Tests of Building Construction and Materials (ref. 10).

Joint systems in smoke barriers must be tested in accordance with the requirements of UL 2079 for air leakage. The air leakage rate of the joint must not exceed 5 cfm per lineal foot of joint (0.00775 m3/s-m) at 0.3 in. of water (7.47 Pa) for both the ambient temperature and elevated temperature tests.

Note that treatments to maintain the fire resistance rating of control joints is also included in ACI 216.1-07/TMS-0216, Code Requirements for Determining Fire Resistance of Concrete and Masonry Construction Assemblies (ref. 11) which is adopted by reference in IBC Section 721.1. These options are also addressed in TEK 07-01D.

Details of concrete masonry fire wall connections to roofs and floors are shown in TEK 05-08B, Detailing Concrete Masonry Fire Walls (ref. 12).

FIRESTOP MATERIAL AND SYSTEMS SELECTION CONSIDERATIONS

When extending the continuity of the wall to and through the penetrating item or items, the appropriate firestop system (or mortar, grout, or concrete) must be selected. Systems selection is the key to appropriate firestopping. Without proper systems selection and installation, the continuity of the fire resistance rated assembly can be compromised.

Several considerations other than fire and smoke need to be accounted for in selecting the firestop system, regardless of the firestop material or assembly type. For example, how much movement is expected in the joint assembly? The firestop system must match the expected movement of the joint to be able to maintain the rated fire resistance. Similarly, any expected movement of the penetrating item must be accommodated. Locking a pipe into a penetration could interfere with the plumbing or piping system performance.

When choosing materials, it is important to note that copper is not compatible with the cement in concrete and may be compromised over time by the mortar, grout or concrete, if used.

For joint systems, there are many configurations of products that make up the firestop ‘system.’ The system may consist of a mineral wool or other backing, packing or damming material, and one of various sealant types including silicone elastomerics, latex or silicone intumescents, latex, or spray system. Plastic piping, insulations, cable trays, and cable penetrating items may have systems comprised of wrap strips, plastic pipe devices, intumescent blocks, and many other products.

A “systems concept” is critical to extending the fire resistance rating and smoke resistant properties of the wall, for both joints and penetrations. In addition, control joint materials must be compatible with the firestop systems selected if the two intersect. The same applies to fire damper assemblies. This compatibility should be verified with both manufacturers. Most importantly, elastomeric control joint materials must allow for the depth of the completed firestop system in the joint. For penetrations, joints or perimeter fire containment, the firestopping must be installed to the tested and listed system in order to be reliable.

Information regarding the Installation, Inspection and Management of Firestop Systems is available at http://www.fcia. org and contained in the FCIA Firestop Manual of Practice (ref. 13). The FCIA Firestop Manual of Practice is free to architects working for design firms, building officials and fire marshals. CMHA does not endorse firestop contractor certification.

MAINTAINING THE FIRE RESISTANCE RATING

The International Fire Code (ref. 14) makes it clear in Section 703.1 that the required fire resistance rating of all fire-resistance rated construction be maintained through proper repair, restoration or replacement as needed. In addition, as building services change, there may be new penetrations required through fire resistance rated concrete masonry assemblies. These new penetrations must also be protected to maintain the integrity of the construction.

Although not required by current building codes, information for on site inspection of firestop systems is provided in ASTM E2174, Standard Practice for On-Site Inspection of Installed Fire Stops (ref. 15) and ASTM E2393, Standard Practice for On-Site Inspection of Installed Fire Resistive Joint Systems and Perimeter Fire Barriers (ref. 16).

REFERENCES

  1. International Building Code. International Code Council, 2006 and 2009.
  2. Fire Resistance Ratings of Concrete Masonry Assemblies, TEK 07-01D. Concrete Masonry & Hardscapes Association, 2018.
  3. Standard Test Method for Fire Tests of Penetration Firestop Systems, ASTM E814-10. ASTM International, Inc., 2010.
  4. Fire Tests of Through-Penetration Firestops, UL 1479. Underwriters Laboratories, 2003.
  5. Standard Test Methods for Fire Tests of Building Construction and Materials, ASTM E119-09c. ASTM International, Inc., 2009.
  6. Standard for Fire Dampers, UL 555. Underwriters Laboratories, 2006.
  7. Standard for Smoke Dampers, UL 555S. Underwriters Laboratories, 1999.
  8. Standard Test Method for Fire-Resistive Joint Systems, ASTM E1966-07. ASTM International, Inc., 2007.
  9. Standard for Tests for Fire Resistance of Building Joint Systems, UL 2079. Underwriters Laboratories, 2004.
  10. Standard for Fire Tests of Building Construction and Materials, UL 263. Underwriters Laboratories, 2003.
  11. Code Requirements for Determining Fire Resistance of Concrete and Masonry Construction Assemblies, ACI 216.1-07/TMS-0216 07. American Concrete Institute and The Masonry Society, 2007.
  12. Detailing Concrete Masonry Fire Walls, TEK 05-08B. Concrete Masonry & Hardscapes Association, 2005.
  13. Firestop Industry Manual of Practice. Firestop Contractors International Association, 2009.
  14. International Fire Code. International Code Council, 2006 and 2009.
  15. Standard Practice for On-Site Inspection of Installed Fire Stops, ASTM E2174-09. ASTM International, Inc., 2009.
  16. Standard Practice for On-Site Inspection of Installed Fire Resistive Joint Systems and Perimeter Fire Barriers, ASTM E2393-10. ASTM International, Inc., 2010.

Detailing Concrete Masonry Fire Walls

  • August 2018

INTRODUCTION

Concrete masonry, due to its inherent durability, reliability and superior fire resistance characteristics, is well suited to a range of fire protection applications.

The International Building Code (IBC) (ref. 1) defines three wall types for fire protection— fire wall, fire barrier and fire partition—depending on the level of protection provided for the type of occupancy and intended use. Of the three defined fire-rated assemblies, a fire wall is generally considered to provide the highest level of robustness and fire safety. As such, it is intended to provide complete separation and must be structurally stable under fire conditions.

Generally, fire barriers and fire partitions are required to provide the minimum protection necessary to assure that building occupants can evacuate a structure without suffering personal injury or loss of life. In addition to these requirements, fire walls reduce the likelihood of fire spread into the adjoining space, thus minimizing major property loss. Potentially significant architectural and economic advantages can be gained from using fire walls since each portion of a building separated by fire walls is considered a separate building for code compliance purposes.

Designing and detailing fire walls is a complex task with many facets, including structural criteria, fire resistance, vertical and horizontal continuity, and criteria for protecting openings and joints. It is beyond the scope of this TEK to include every code provision and exception for fire wall design for all project conditions. While much of the information in this TEK is applicable to both the IBC and the NFPA 5000 (ref. 2) building codes, the provisions are based on the 2003 IBC, so certain provisions may be different from NFPA 5000 requirements. Hence, the information may or may not conform to local building code requirements and should be carefully reviewed to ensure compliance. In addition, the details shown here are not the only ones that will comply, but are included as examples. Project specific needs will dictate the final detailing decisions.

FIRE WALLS

By Code (ref. 1), fire walls are required to have the minimum fire-resistance rating acceptable for the particular occupancy or use group which they separate and must also have protected openings and penetrations. A fire wall must have both vertical and horizontal continuity to ensure that the fire does not travel over, under or around the fire wall. In addition, the wall must have sufficient structural stability under fire conditions to remain standing for the duration of time indicated by the fire-resistance rating even with the collapse of construction on either side of the fire wall.

Fire-Resistance Rating

Because fire walls provide a complete separation between adjoining spaces, each portion of the structure separated by fire walls is considered to be a separate building. Fire walls in all but Type V construction must be constructed of approved noncombustible materials. Table 1 shows minimum required fire-resistance ratings. Information on determining the fire-resistance ratings of concrete masonry assemblies is contained in Fire Resistance Rating of Concrete Masonry Assemblies, TEK 07-01D and Standard Method for Determining Fire Resistance of Concrete and Masonry Construction Assemblies (refs. 3, 4).

Protected Openings and Penetrations

The IBC states that fire walls must have closures such as fire doors or shutters which automatically activate to secure the opening in the event of a fire. Further, openings in fire walls are restricted to a maximum size of 120 ft2 (11.2 m2). An exception permits larger openings provided both buildings separated by the fire wall are equipped throughout with automatic sprinkler systems. In all cases, the aggregate width of all openings at any floor level is limited to 25 percent of the wall length.

Through-penetrations in fire walls must utilize either fire-resistance rated assemblies or a firestop system which is tested in accordance with either ASTM E 814 (ref. 5) or UL 1479 (ref. 6). The annular space between steel, iron or copper pipes or steel conduits and surrounding concrete masonry fire walls may be filled with concrete, grout or mortar for the thickness required to provide a fire-resistance rating equivalent to the fire-resistance rating of the wall penetrated. In addition, the penetrating item is limited to a 6-in. (152-mm) nominal diameter and the opening is limited to 144 in.2 (92,900 mm2). Openings for steel electrical outlet boxes are permitted provided they meet the Code specified requirements.

Combustible members, such as wood, are permitted to be framed into concrete masonry fire walls provided that, when framed on both sides of the wall, there is at least 4 in. (102 mm) between the embedded ends of the wood framing. The full thickness of the fire wall 4 in. (102mm) above and below, as well as in between, the combustible member must be filled with noncombustible materials approved for fireblocking.

Voids created at the junction of walls and floor/ceiling/ roof assemblies must be protected from fire passage by using fireresistant joint systems tested in accordance with ASTM E 1966 or UL 2079 (refs. 7, 8). Control joints in fire walls must have fire-resistance ratings equal to or exceeding the required rating of the wall. Recommendations for locating and spacing control joints in concrete masonry walls also apply to concrete masonry fire walls. Crack Control Strategies for Concrete Masonry Construction, CMU-TEC 009-23 (ref. 9) includes control joint spacing criteria and illustrates control joint details for various fire-resistance ratings.

Vertical and Horizontal Continuity

The IBC mandates vertical continuity of a fire wall by requiring that the wall extend continuously from the foundation to a termination point at least 30 in. (762 mm) above both adjacent roofs. Exceptions permitting the fire wall termination at the underside of the roof deck or slab are listed in the Code. These exceptions require the use of Class B roof coverings (minimum), no openings within 4 ft (1.22 m) of the fire wall and other criteria for roof assembly protection. Buildings located over parking garages and stepped buildings are subject to additional requirements and permitted exceptions.

Horizontal continuity limits the spread of fire around the ends of a fire wall. The IBC requires that fire walls be continuous from exterior wall to exterior wall and that they extend at least 18 in. (457 mm) beyond the exterior surface of exterior walls. As with the vertical continuity requirements, there are criteria for terminating the fire wall at the interior surface of an exterior wall based on the types and fire resistance ratings of the intersecting wall constructions and on the presence of an automatic sprinkler system installed per Code requirements.

Structural Stability Under Fire Conditions

While concrete masonry remains structurally stable during the extreme temperatures experienced under fire conditions, steel framing undergoes a reduction in strength as the surrounding temperature and duration of exposure are increased. This decreased structural capacity is evidenced by a dramatic increase in the deflection and twisting of steel members. Wood framing may burn, collapse, shrink and/or deform under fire exposure and it too loses its load-carrying capability. For these reasons, concrete masonry firewalls should be designed and detailed to withstand any loading imposed by fire-compromised framing systems or detailed so that those loads are not imparted to the fire wall during a fire. This is perhaps the most difficult detailing provision in fire wall design.

DETAILING CONSIDERATIONS FOR STRUCTURAL STABILITY

Because most fire wall criteria relating to fire-resistance rating, protected openings and penetrations, and vertical and horizontal continuity are prescriptive, the designer’s primary challenge when engineering and detailing a concrete masonry fire wall relates to maintaining the structural stability of the wall under fire conditions.

There are various methods of designing, detailing and constructing fire walls for structural stability during a fire. Among the systems recommended for use as fire walls are: (a) cantilevered or freestanding walls, (b) laterally supported and tied walls, and (c) double wall construction.

Cantilevered or Freestanding Walls

Cantilevered walls (Figure 1) do not depend on the roof framing for structural support. The wall is cantilevered from the foundation by grouting and reinforcing, or by prestressing. Freestanding walls may also be designed to span horizontally between pilasters or masonry columns integral to the wall.

It can be difficult to design a cantilevered single wythe loadbearing fire wall. Thermal stresses may cause deformation in steel or wood joists or framing systems which can eccentrically load the top of the fire wall. Designing the wall to remain stable under that loading condition may be difficult especially for tall or slender walls. For this reason, cantilevered single wythe fire walls are often designed as nonbearing walls with the primary roof framing system running parallel to the fire wall. Column lines on either side of the wall support the roof framing. Details for cantilevered/freestanding fire walls are similar to those for laterally supported walls (shown in Figures 2, 3 and 4) with the exception that cantilevered walls do not include through-wall ties or break-away connectors.

Laterally Supported or Tied Walls

Laterally supported or tied walls rely on the building frame for lateral stability. The fire wall is laterally supported on each side by the framing system. As such, forces due to the collapse of the structure on one side of the fire wall are resisted by the structural framework on the other side of the wall. Adequate clearance, as listed in Table 2, between the framing and the concrete masonry fire wall is necessary to allow framing expansion or deformation without exerting undue pressure on the wall.

Laterally supported fire walls may utilize break-away connectors
manufactured with metals having melting points lower than structural steel (generally about 800° F (427° C)), so that, in the event of fire, the connectors on the fire side of the wall will give way before those on the non-fire side. In Figures 2 and 3, the structural diaphragm on the side of the wall opposite the fire provides the stability. The connections between the roof and wall must be designed to resist these forces. If the diaphragms occur at different elevations, the wall must be designed to withstand the anticipated flexural forces that will be generated as well. Figure 4 shows a laterally supported fire wall with combustible framing supported by metal joist hangers. Joist hanger manufacturers may have alternate details as well. Note that there may be code limitations on the use of combustible framing.

Figure 5 shows design and detailing options for tied fire walls. Tied fire walls are a type of laterally supported fire wall where the roof structure is not supported by the fire wall, but rather by the roof structure on the other side of the fire wall, thus the two roof structures are tied together across the fire wall. Figure 5a illustrates one choice for a “double column” detail which uses a through-wall tie to connect the primary steel on both sides of the fire wall. In this detail, the primary roof framing steel is parallel to the fire wall and supported on fireproofed columns. One column is used on each side of the fire wall to support the roof system for that building. Both steel columns and primary support beams/trusses should be aligned vertically and horizontally with the columns and beams/trusses on the opposite side of the wall and should be fireproofed. If the primary steel is not parallel to the fire wall Figure 5b shows a through-wall tie which can be used.

As an alternative to using two steel columns, Figure 5c shows one steel support column encased entirely within the concrete masonry fire wall. Fire protection requirements for steel columns are included in Steel Column Fire Protection, TEK 07-06A (ref. 11). This system creates a single column line tied at the top of the wall to horizontal roof framing. Detailing the connection of the steel beams to the concrete masonry fire wall varies based on the framing layout, but the wall must be supported at the top and the connection must be fire protected.

Double Wall Fire Wall

Double wall construction (Figure 6) is generally easy to design and detail for loadbearing conditions, especially for taller walls. It utilizes two independent concrete masonry walls side by side, each meeting the required fire-resistance rating. In the event one wall is pulled down due to fire, the other wall remains intact, preventing fire spread. Floor and roof connections to each fire wall are the same as for conventional concrete masonry construction. These walls are often cantilevered or freestanding but may be tied or laterally supported as well if so detailed and designed. This system is also easy to use when a building addition requires a fire wall between the existing structure and the new construction.

REFERENCES

  1. International Building Code 2003. International Code Council, 2003.
  2. Building Construction and Safety Code – 2003 Edition, NFPA 5000. National Fire Protection Association, 2003.
  3. Fire Resistance Rating of Concrete Masonry Assemblies, CMHA TEK 07-01D. Concrete Masonry & Hardscapes Association, 2018.
  4. Standard Method for Determining Fire Resistance of Concrete and Masonry Construction Assemblies, ACI 216.1-97/ TMS 0216-97.
    American Concrete Institute and The Masonry Society, 1997.
  5. Standard Test Method for Fire Tests of Through Penetration Fire Stops, ASTM E 814-02. ASTM International, 2002.
  6. Fire Tests of Through-Penetration Firestops, UL
  7. Underwriters Laboratory, 2003.
  8. Standard Test Method for Fire-Resistive Joint Systems, ASTM E 1966-01. ASTM International, 2001.
  9. Tests for Fire Resistance of Building Joint Systems, UL
  10. Underwriters Laboratory, 2004
  11. Crack Control Strategies for Concrete Masonry Construction, CMU-TEC-009-23. Concrete Masonry & Hardscapes Association, 2023.
  12. Criteria for Maximum Foreseeable Loss Fire Walls and Space Separation, Property Loss Prevention Data Sheets 1-22. Factory Mutual Insurance Company, 2000.
  13. Steel Column Fire Protection, CMHA TEK 07-06A. Concrete Masonry & Hardscapes Association, 2003.