TECHNICAL NOTE On Cold-Formed Steel Construction 1201 15th Street, NW, Suite 320 W ashington, DC 20005 (202) 785-2022 $5.00 SUGGESTED COST-EFFECTIVE COLD-FORMED STEEL FIRE AND ACOUSTIC-RATED WALL AND FLOOR/ CEILING ASSEMBLIES FOR MULTI-UNIT STRUCTURES Summary: This Technical Note addresses some of the most common types of assemblies used with multi-unit construction. Although not all-inclusive, the rated assemblies contained herein are included to help the designer, specifier, and builder achieve cost-effective construction with cold-formed steel (CFS) framing. Additional references and methodologies are included to allow specifiers or inspectors who want a more indepth treatment of the subject or additional information on a particular assembly to easily find this information. Disclaimer: Designs cited herein are not intended to preclude the use of other materials, assemblies, structures or designs when these other designs and materials demonstrate equivalent performance for the intended use; CFSEI documents are not intended to exclude the use and implementation of any other design or construction technique. INTRODUCTION With the advent of new designs and systems with cold-formed steel framing, as well as steel framing standards being incorporated into building codes, designers are realizing the economy and benefit of using steel framing for multi-family and multi-story construction. Common uses include hotels, motels, dormitories, apartments, condominiums, barracks, assisted living facilities, and other structures where light-framed systems are advantageous. Most of these construction types have repetitive floor-tofloor designs, relatively short spans across units (less than 20 feet), alignment of bearing and shear walls between floors, simple to moderate building geometry, and moderate to complex roof geometry. Also, because of safety, constructability, and building limitations, combustibility is an issue. The light weight of steel framing as compared to concrete or masonry structures gives an added benefit in high seismic regions. DESIGN Rated assemblies are not required in all areas of all structures, and it is beyond the scope of this note to show where it would be required by code to use a particular rating. However, in both multi-unit and mixed-use construction, fire ratings are required between occupancy types, and acoustic ratings are desirable both between living units and between occupancies. FIRE RATING AND TESTING Design professionals and builders are sometimes unclear as to what is really meant when an assembly is a one hour wall or a two hour floor ceiling assembly. A one hour rating does NOT mean that the wall is guaranteed to last one hour in a fire, nor does it mean that the elements of the assembly have specific minute ratings, and when they are all put together the total rating of the individual parts meets or exceeds 60 minutes. What it does mean is that under laboratory controlled conditions, a specimen (built with the exact components listed in the assembly) was able to pass a test where heat and flame was applied to one side, and heat sensors were monitored on the unexposed side. A passing assembly is one that keeps the maximum temperature on the unexposed side at or below 250 degrees Fahrenheit plus the ambient room temperature. Model building codes require one or two-hour ratings that are based on laboratory testing done in accordance with ASTM E119: Standard Test Methods for Fire Tests of Building Construction and Materials. Additional information about the exact methodology of the test is included in LGSEA Technical Note 420: Fire Rated Assemblies of Cold-Formed Steel Construction. ACOUSTIC RATING AND TESTING There are two primary types of acoustic ratings. The first rating is the Sound Transmission Class (STC), which measures an assembly s ability to block airborne sound transmission. STC is reported as a numerical value, and higher values represent a better ability to Cold-Formed Steel Engineers Institute 1 TECH NOTE T001-09 November 2009
block airborne sounds. There are two tests to determine STC. The laboratory test is based on ASTM E90, and the field test is based on ASTM E413. The key difference is the laboratory test measures only sound passing through the assembly. The field test measures all sound, which could have other transmission paths: adjacent floors or walls, openings, and structural elements such as beams and columns. The second rating is the Impact Insulation Class (IIC), which measures an assembly s ability to block impact sound transmitted through the assembly and structure. Impact sound transmission arises from a variety of sources, most notably the movement of people within a building. Examples of impact sounds include an individual walking with hard shoes on a tile floor or the slamming of doors. Like STC values, IIC also is reported as a numerical value, and higher values represent less sound transmission (and thus better ability to block sounds). The procedure for the IIC test is delineated in ASTM E492 and E989. The numerical value STC and IIC ratings are developed by analyzing sound pressure levels and averaging over 16 different frequency bands. More information on acoustic tests and resources is available in LGSEA Technical Note 360: Acoustic Insulation and Sound Transmission in Cold-Formed Steel Construction. Special Disclaimer on Cost Data: The cost data presented in the tables is based on the RS Means 2009 CostWorks software. The costs are based on United States national average costs and do not reflect local conditions. The end user should verify any local adjustments to these costs. The installed costs include the installer's overhead and profit, but do not include general conditions for a project. CODE REQUIREMENTS The 2006 International Building Code (IBC) contains specific minimum requirements for fire and acoustic ratings. Section 711, Horizontal Assemblies, of the IBC specifies the instances where floor assemblies are required to have a fire resistance rating. IBC sections 704 Exterior Walls, 705 Fire Walls, 706 Fire Barriers, 707 & 708 Fire Partitions specify the fire resistance requirements for walls. The ratings for load bearing walls are also required to comply with IBC table 601 depending on the building's type of construction. Section 1207.2 requires that wall and ceiling assemblies that separate dwelling units have a minimum STC rating of 50. In addition, section 1207.3 requires that floors also have a minimum IIC rating of 50. Following are tables that give information about some of the most common types of assemblies used with multiunit construction. Although not all-inclusive, the rated assemblies are included to help the designer, specifier, and builder achieve cost-effective construction with coldformed steel (CFS) framing. TECH NOTE T001-09 November 2009 2 Cold-Formed Steel Engineers Institute
TABLE 1: FLOOR / CEILING ASSEMBLIES Combustible Non-Combustible Criterion Wood Framing CFS Framing CFS Framing UL Assembly # L570 L527 G549 FC 1142 GA-600-2006 File # FC 5011 N/A FC 1143 Fire Rating 1 Hour 1-1/2 Hours 1 Hour Floor Construction Typical Joist 5 1/4" Acoustical Mat 1/2" Gypsum Topping on 19/32" Plywood 9-1/2" I-Joists 3/4" Plywood 3 1000S162-54 Fy = 50ksi 1-3/8" Normal Wt Conc on 28 ga. Steel Deck (2" Total) 3 1000S162-54 Fy = 50ksi Typical Framing Spacing 19.2" oc 24" oc 16" oc Resilient Channel Spacing 16" oc 16" oc 24" oc Layers of Gypsum 2 (1/2" or 5/8") 2 (5/8") 2 (1/2") STC Rating 60 1 51 2 CAR-UND 66 2 GFB, RC 60 2 NI, RC IIC Rating 54 1 CT, GFB, AM 58 1 SV, GFB, AM 62 1 LAM, GFB, AM 70 2 CAR-UND 34 2,4 GFB, RC <30 2,4 NI, RC Material Cost $/sf $ 6.44 $ 3.56 $ 5.61 Installed Cost $/sf Closed Shop $ 13.27 $ 9.42 $ 12.28 Floor Section Detail Sound Transmission Data Source Notes: Table Notes 1 GA-600-2006 Fire Resistance Design Manual. Sound ratings for this assembly are based on a joist spacing of 24" oc and a proprietary acoustical mat. 2 Steel Framing Alliance-A Guide to Fire & Acoustic Data for Steel Floor, Wall & Roof Assemblies (December 2007) 3 In UL designs, minimum size for this assembly is less than that shown. Larger sizes are permitted. 4 IIC values may be improved with the use of sound isolation mats and carpet with underlayment. 5 Framing sizes in the table are for comparison purposes only. Longer and shorter spans are possible for both wood and steel assemblies with the configurations shown. An assumed span of 15'-0" has been used to create an equal comparison of the framing systems. Abbreviations in Sound Data: AM = Acoustical Mat CAR-UND = Carpet & Underpad CT = Ceramic Tile GFB = Glass Fiber Batts (with thickness) LAM = Laminate Flooring NI = No Insulation RC = Resilient Channels Included SV = Sheet Vinyl Cold-Formed Steel Engineers Institute 3 TECH NOTE T001-09 November 2009
TABLE 2: LOADBEARING 1-HOUR AND 2-HOUR WALLS Criterion 1 Hour Fire Rating 2 Hour Fire Rating Wood Framing (Combustible) UL Assembly # U305 U423 U425 U334 GA-600-2006 File # WP 3242 N/A 5 Typical Wall Stud 2 x 4 CFS Framing (Non-Combustible) Wood Framing (Combustible) CFS Framing (Non-Combustible) 6 U423 7 U425 WP 1206 - N/A WP 1716 Fy = 33ksi 2 x 4 Fy = 33ksi Typical Spacing 16" oc 16" oc 16" oc 24" oc Layers of Gypsum 1 One Side (5/8") 2 @ RC Side (5/8") 1 Each Side (5/8") 2 Each Side (5/8") 2 Each Side (5/8") Resilient Channel Spacing 16" oc 24" oc 24" oc 24" oc 50 1 50 3 RC, RFB (3- RC, RFB (3") 1/2") STC Rating 60 4 RC, RFB (2") 55 4 RC, RFB (3") Material Cost $/sf $ 1.90 $ 1.77 $ 2.28 $ 2.45 Installed Cost $/sf Closed Shop $ 7.62 $ 5.97 $ 8.08 $ 7.71 Wall Plan Detail Table Notes Sound Transmission Data Source Notes: 1 GA-600-2006 Fire Resistance Design Manual 2 Steel Framing Alliance-A Guide to Fire & Acoustic Data for Steel Floor, Wall & Roof Assemblies (December 2007) 3 Sound estimation based on SOCRATES estimation software. See the Steel Framing Alliance guide for additional information. 4 Sound data is based on GA-600 assembly WP 3010 for the 2 hour wood assembly and WP 1470 for the CFS framed wall Abbreviations in Sound Data: RC = Resilient Channels Included RFB = Rock Fiber (mineral wool) Batts (with thickness) Framing Notes: 5 Framing member thickness/lumber grade may increase with structural requirements at lower floors. 6 UL U423 requires rock fiber insulation for full structural design load capacity. See UL directory for exact requirements. 7 80% of full structural load capacity for assembly UL U425. TECH NOTE T001-09 November 2009 4 Cold-Formed Steel Engineers Institute
TABLE 3: LOADBEARING 1-HOUR AND 2-HOUR PARTY WALLS 1 Hour Fire Rating 2 Hour Fire Rating Wood Framing CFS Framing Wood Framing CFS Framing Criterion (Combustible) (Non-Combustible) (Combustible) (Non-Combustible) UL Assembly # U376 V446 5 - V446 5 GA-600-2006 File # - WP 1024 WP 3820 WP 1516 Typical Wall Stud 4 2 x 4 Fy = 33ksi 2 x 4 Fy = 33ksi Typical Spacing 16" oc 24" oc 16" oc 24" oc Layers of Gypsum 1 Ext. Sides (5/8") 1 Ext. Sides (5/8") 2 Ext. Sides (5/8") 2 Ext. Sides (5/8") STC Rating 56 3 GFB (2-1/2") 50 1 GFB (3-1/2"), AIR (2") 55 1 GFB (3-1/2"), AIR (1") 55 1 GFB (3-1/2"), AIR (2") Material Cost $/sf $ 1.79 $ 2.42 $ 2.47 $ 3.20 Installed Cost $/sf Closed Shop $ 6.82 $ 6.80 $ 8.56 $ 8.54 Wall Plan Detail Table Notes Sound Transmission Data Source Notes: 1 GA-600-2006 Fire Resistance Design Manual 2 Steel Framing Alliance-A Guide to Fire & Acoustic Data for Steel Floor, Wall & Roof Assemblies (December 2007) 3 Sound estimation based on SOCRATES estimation software. See the Steel Framing Alliance guide for additional information. Abbreviations in Sound Data: AIR = Layer of Air (with thickness) GFB = Glass Fiber Batts (with thickness) Framing Notes: 4 Framing member thickness/lumber grade may increase with structural requirements at lower floors. 5 80% of full structural load capacity for assembly UL V446 (1 hour only). See UL directory for exact requirements. There is no reduction for the 2 hour assembly. Lateral bracing is required for this UL assembly and walls are to be constructed with separate top and bottom tracks. Cold-Formed Steel Engineers Institute 5 TECH NOTE T001-09 November 2009
DATA ESTIMATION Some of the sound data that has been incorporated into this Technical Note was based on: Warnock, A.C.C., Estimation of Sound Transmission Class and Impact Insulation Class Rating for Steel Framed Assemblies, Research Report RP08-7, Steel Framing Alliance, 2008. The above report has surveyed existing published sound test reports. Those reports, although not listed in these tables, are denoted in the source column of the Steel Framing Alliance AGuide to Fire and Acoustic Data for Steel Floor, Wall and Roof Assemblies by an alphanumeric acoustic test identifier. Letter prefixes in the identifier denote various acoustic testing laboratories. The Warnock report also provides numerous acoustic estimates. Acoustic estimates were made with an acoustic sound classification rating estimator, called SOCRATES, that is available from the National Research Council of Canada. Further information on accessing and downloading SOCRATES is listed in the preface notes of the Steel Framing Alliance guide. FUTURE RESEARCH The CFSEI Fire and Acoustic Task Group has identified research needs for testing of assemblies to meet minimum code requirements. Primarily, the testing will be acoustic STC tests on existing fire rated assemblies. As additional needs arise, testing will be evaluated and prioritized. Specifiers should be aware that acoustic performances of the assemblies shown can be greatly improved by using some of the proprietary products currently on the market. Most notably, gaskets, isolators, sheathing products and other devices can often be added or substituted without compromising the fire rating of an acoustic partition. CONCLUSION The assemblies listed are only a few of the hundreds of assemblies available using Cold-Formed Steel Framing. For a comprehensive listing of both proprietary and nonproprietary assemblies, including roof-ceiling and exterior wall assemblies not covered by this note, the Steel Framing Alliance has a searchable directory both online and available for download at www.steelframing.org. The CFSEI also maintains two Technical Notes originally published by the Light Gauge Steel Engineers Association (LGSEA). They are Fire Rated Assemblies of Cold-Formed Steel Construction (TN 420) and Acoustic Insulation and Sound Transmission in Cold-Formed Steel Construction (TN 360). In addition, many manufacturers of proprietary acoustic products have performed testing with steel framing products, and have data available as a part of their product literature. CONTRIBUTORS This publication was developed by the CFSEI Fire and Acoustic Task Group, and is intended to provide designers, specifiers and builders with guidance on construction using cold-formed steel framing that is safe and cost-effective. CFSEI acknowledges Matthew Saari, P.E., Don Allen, P.E., and the entire Fire and Acoustic Task Group, Ray Frobosilo Sr., Super Stud Building Products, Inc., chairman, responsible for development of this Technical Note. CFSEI is grateful to the American and Iron and Steel Institute, Steel Stud Manufacturers Association and all the companies and organizations whose members contributed their time and knowledge to the Fire and Acoustic Task Group during development of this CFSEI Technical Note. CFSEI also extends sincere appreciation to RSMeans, a product line of Reed Construction Data. RSMeans provides accurate and timely cost information for projecting the cost of both new building construction and renovation projects. References CFSEI Technical Review Committee: Rob Madsen, P.E., Devco Engineering, Inc., chairman. 1. ASTM E90-04 Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements 2. ASTM E119-08a Standard Test Methods for Fire Tests of Building Construction and Materials 3. ASTM E413-04 Classification for Rating Sound Insulation 4. ASTM E492-04 Standard Test Method for Laboratory Measurement of Impact Sound Transmission Through Floor-Ceiling Assemblies Using the Tapping Machine 5. ASTM E989-06 Standard Classification for Determination of Impact Insulation Class (IIC) 6. A Guide to Fire & Acoustic Data for Steel Floor, Wall & Roof Assemblies, 8th Edition. 2009, Steel Framing Alliance, August 2009 7. International Building Code, 2006 Edition 2006, International Code Council, Inc. 8. Residential Steel Framing Builders Guide. U. S. Department of Housing and Urban Development, Partnership for Advancing Technology in Housing (PATH) 9. Warnock, A.C.C., Estimation of Sound Transmission Class and Impact Insulation Class Rating for Steel Framed Assemblies, Research Report RP08-7, Steel Framing Alliance, 2008. This Technical Note on Cold-Formed Steel Construction is published by the Cold-Formed Steel Engineers Institute ( CFSEI ). The information provided in this publication shall not constitute any representation or warranty, express or implied, on the part of CFSEI or any individual that the information is suitable for any general or specific purpose, and should not be used without consulting with a qualified engineer, architect, or building designer. ANY INDIVIDUAL OR ENTITY MAKING USE OF THE INFORMATION PROVIDED IN THIS PUBLICATION ASSUMES ALL RISKS AND LIABILITIES ARISING OR RESULTING FROM SUCH USE. CFSEI believes that the information contained within this publication is in conformance with prevailing engineering standards of practice. However, none of the information provided in this publication is intended to represent any official position of the CFSEI or to exclude the use and implementation of any other design or construction technique. TECH NOTE T001-09 November 2009 6 Cold-Formed Steel Engineers Institute