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le="text-align: justify; text-indent: 2em; margin-top: 0px; margin-bottom: 0px; -ms-text-justify: inter-ideograph;">17'-6"
2 x 12 x 68
27'-8"
25'-1"
21'-11"
25'-1"
22'-10"
19'-11"
2 x 12 x 97
30'-9"
27'-11"
24'-5"
27'-11"
25'-4"
22'-2"
For SI: 1 inch = 25.4 mm, 1 psf = 0.0479 kN/m2, 1 foot = 0.3m.
1Table provides the maximum clear span in feet and inches.
2Bearing stiffeners shall be installed at all support points and concentrated loads.
3Deflection criteria: L/480 for live loads; L/240 for total loads.
4Floor dead load = 10 psf (0.479 kN/m2)
5For actual size refer to Table 2.1.
Table 5.4
Allowable Spans For Cold-Formed Steel Floor Joists1,2,3,4,5,6
Multiple Spans
33 ksi Steel
| Nominal Joist | 30 psf Live Load | 40 psf Live Load | ||||
| Size 7 | Spacing (inches) | Spacing (inches) | ||||
| 12 | 16 | 24 | 12 | 16 | 24 | |
| 2 x 6 x 33 | 12'-10" | 10'-6" | 7'-10" | 11'-0" | 9'-0" | 6'-7" |
| 2 x 6 x 43 | 15'-8" | 13'-6" | 11'-0" | 14'-0" | 12'-1" | 9'-10" |
| 2 x 6 x 54 | 17'-7" | 15'-3" | 12'-5" | 15'-9" | 13'-8" | 11'-2" |
| 2 x 6 x 68 | 19'-6" | 17'-2" | 14'-0" | 17'-8" | 15'-4" | 12'-6" |
| 2 x 6 x 97 | 21'-7" | 19'-7" | 16'-8" | 19'-7" | 17'-10" | 14'-11" |
| 2 x 8 x 33 | 12'-9" | 10'-2" | 7'-1" | 10'-9" | 8'-6" | 5'-8" |
| 2 x 8 x 43 | 19'-5" | 16'-8" | 12'-6" | 17'-5" | 14'-3" | 10'-8" |
| 2 x 8 x 54 | 23'-0" | 19'-11" | 16'-3" | 20'-6" | 17'-9" | 14'-6" |
| 2 x 8 x 68 | 25'-10" | 22'-5" | 18'-3" | 23'-2" | 20'-0" | 16'-4" |
| 2 x 8 x 97 | 29'-4" | 26'-7" | 21'-11" | 26'-7" | 24'-0" | 19'-7" |
| 2 x 10 x 43 | 20'-3" | 16'-5" | 12'-1" | 17'-3" | 13'-11" | 10'-2" |
| 2 x 10 x 54 | 25'-6" | 22'-1" | 18'-0" | 22'-10" | 19'-9" | 15'-6" |
| 2 x 10 x 68 | 30'-6" | 26'-5" | 21'-7" | 27'-4" | 23'-8" | 19'-3" |
| 2 x 10 x 97 | 35'-4" | 31'-9" | 25'-11" | 32'-1" | 28'-5" | 23'-2" |
| 2 x 12 x 43 | 19'-8" | 15'-9" | 11'-3" | 16'-7" | 13'-3" | 9'-0" |
| 2 x 12 x 54 | 27'-8" | 23'-9" | 17'-10" | 24'-9" | 20'-4" | 15'-2" |
| 2 x 12 x 68 | 32'-7" | 28'-3" | 23'-0" | 29'-2" | 25'-3" | 20'-7" |
| 2 x 12 x 97 | 41'-3" | 36'-7" | 29'-10" | 37'-5" | 32'-9" | 26'-9" |
For SI: 1 inch = 25.4 mm, 1 psf = 0.0479 kN/m2, 1 foot = 0.3m.
1Table provides the maximum clear span in feet and inches to either side of the interior support.
2Interior bearing supports for multiple span joists shall consist of structural (bearing) walls or beams.
3Bearing stiffeners shall be installed at all support points and concentrated loads.
4Deflection criteria: L/480 for live loads; L/240 for total loads.
5Floor dead load = 10 psf (0.479 kN/m2)
6Interior supports shall be located within two feet (610 mm) of mid span provided that each of the
resulting spans does not exceed the appropriate maximum span shown in the table above.
7 For actual size refer to Table 2.1.
,PRESCRIPTIVE METHOD FOR RESIDENTIAL COLD-FORMED
STEEL FRAMING
Second Edition
Prepared for
The U.S. Department of Housing
and Urban Development
Office of Policy Development and Research
Washington, DC
Co-Sponsored by
The American Iron and Steel Institute
Washington, DC
and
The National Association of Home Builders
Washington, DC
by
NAHB Research Center, Inc.
400 Prince George's Boulevard
Upper Marlboro, MD 20774-8731
August 1997
CONTENTS
5.0STEEL FLOOR FRAMING21
5.1Floor Construction21
5.2Floor to Foundation or Bearing Wall Connection21
5.3Allowable Joist Spans21
5.4Joist Bracing21
5.5Floor Cantilevers22
5.6Splicing22
5.7Framing of Floor Openings22
5.8Floor Trusses22
5.0STEEL FLOOR FRAMING
5.1Floor Construction
Cold-formed steel framing members shall comply with the provisions of Section 2.0. Steel floors shall be constructed in accordance with this section and Figure 5.1.
5.1.1Applicability Limits
The applicability limits of Section 1.3 and Table 1.1 shall apply.
5.1.2In-Line Framing.
Load bearing steel floor framing, wall framing, and ceiling/roof framing shall be constructed in-line with the vertical load bearing members (i.e. studs) located below. A maximum tolerance of 3/4 inch (19 mm) between the centerlines of the in-line members shall be permitted in accordance with Figure 1.2.
5.2Floor to Foundation or Bearing Wall Connection
Cold-formed steel floor framing shall be anchored to foundations, wood sills, or load bearing walls in accordance with Table 5.1 and Figures 5.1 through 5.10. Fastening of steel joists to other framing members shall be in accordance with Table 5.2.
5.3Allowable Joist Spans
The clear span of cold-formed steel floor joists shall not exceed the limits set forth in Table 5.3 for single spans and Table 5.4 for multiple spans. When continuous joist members are used for multiple spans, the interior bearing supports shall be located within two feet (0.6 m) of mid-span of the steel joists, and the individual spans shall not exceed the applicable spans in the table. Floor joists shall have a bearing support length of not less than 1.5 inches (38 mm) for exterior wall supports and 3.5 inches (89 mm) for interior wall supports. Bearing stiffeners shall be installed at each joist bearing location in accordance with Section 2.9. The thickness of joist tracks shall be a minimum of 33 mils (0.84 mm) thick except when used as part of floor header or trimmer in accordance with Section 5.7.
5.4Joist Bracing
The top flanges of floor joists shall be laterally braced by the application of floor fastened to the joists in accordance with Table 5.2. Floor joists with spans that exceed 12 feet (3.7 m) shall have the bottom flanges laterally braced in accordance with one of the following:
1. Gypsum board installed with minimum#6 screws in accordance with the
applicable building code, or
2. Continuous steel strapping installed in accordance with Figure 5.1 and 5.2. Steel straps shall be at least 1-1/2 inches (38 mm) in width and 33 mils (0.84 mm) in thickness. Straps shall be fastened to the bottom flange of each joist with at least one #8 screw and shall be fastened to blocking with at least two #8 screws. Blocking or bridging (X-bracing) shall be installed between joists at a maximum spacing of 12 feet (3.7m) measured along the continuous strapping (perpendicular to the joist run). Blocking or bridging shall also be located at the termination of all straps.
5.5 Floor Cantilevers
Floor cantilevers for the second floor of a two-story building or the first floor of a one-story building shall not exceed 24 inches (610 mm) as illustrated in Figure 5.1. Cantilevers shall support interior floor loading only. Cantilevers, not exceeding 24 inches (610 mm) and supporting one floor and roof (first floor of a two story building), shall be permitted provided that all cantilevered joists are doubled (nested or back-to-back). The doubled cantilevered joists shall extend a minimum of 6 feet (1.8 m) toward the inside and shall be fastened with a minimum of two #8 screws spaced at 24 inches (610 mm) on center through the webs (for back-to-back) or flanges (for nested joists). Approved design is required for cantilevered areas supporting uniform live loads greater than 40 psf (1.92 kN/m2).
5.6Splicing
Joists and other structural members shall not be spliced without an approved design. Splicing of tracks shall conform with Figure 5.11.
5.7Framing of Floor Openings
Openings in floors shall be framed with header and trimmer joists. Header joist spans shall not exceed 8 feet (2.4 m) in length. Header and trimmer joists shall be fabricated from joist and track sections, which shall be of a minimum size and thickness as the adjacent floor joists and shall be installed in accordance with Figures 5.1, 5.12, and 5.13. Each header joist shall be connected to trimmer joists with a minimum of four 2 inch x 2 inch (51 mm x 51 mm) clip angles. Each clip angle shall be fastened to both the header and trimmer joists with four #8 screws evenly spaced on each leg of the clip angle. The clip angles shall have a thickness not less than that of the floor joist.
5.8Floor Trusses
Cold-formed steel floor trusses shall be designed, braced, and installed in accordance with an approved design. Truss members shall not be notched, cut, or altered in any manner unless by an approved design. All trusses shall be aligned with load carrying members (i.e. studs) in the wall. Refer to AISI publication RG-9518 [17] “Design Guide For Cold-Formed Steel Trusses” for additional guidance.
Table 5.1
Floor to Foundation or Bearing Wall Connection Requirements
| Framing Condition | Wind Speed (mph), Exposure, and Seismic Zones 1,2 | ||
| Up to 90 A/B or 70 C or Seismic Zones 0, 1, 2, & 3 | Up to 110 A/B or 90 C or Seismic Zone 4 | Up to 110 C | |
| Floor joist to wall track of exterior steel load bearing wall per Figure 5.3 | 2 - #8 screws | 3- #8 screws | 4- #8 screws |
| Joist track or end joist to bearing wall top track per Figure 5.3 | 1- #8 screw at 24" o.c | 1- #8 screw at 24" o.c. | 1- #8 screw at 12" o.c. |
| Floor joist track or end joist to wood sill per Figure 5.4 | Steel plate spaced at 4’ o.c. with 4-No. 8 screws and 4-10d or 6-8d common nails | Steel plate spaced at 2’ o.c. with 4-No. 8 screws and 4-10d or 6-8d common nails | Steel plate spaced at 1’ o.c. with 4-No. 8 screws and 4-10d or 6-8d common nails |
| Floor joist track or end joist to foundation per Figure 5.5 | 1/2" minimum diameter anchor bolt and clip angle spaced at 6’ o.c. with 8- #8 screws | 1/2" minimum diameter anchor bolt and clip angle spaced at 4’ o.c. with 8- #8 screws | 1/2" minimum diameter anchor bolt and clip angle spaced at 2’ o.c. with 8- #8 screws |
| Cantilevered joist to foundation per Figure 5.6 | 1/2" minimum diameter anchor bolt and clip angle spaced at 6’ o.c. with 8- #8 screws | 1/2" minimum diameter anchor bolt and clip angle spaced at 4’ o.c. with 8- #8 screws | 1/2" minimum diameter anchor bolt and clip angle spaced at 2’ o.c. with 8- #8 screws |
| Cantilevered joist to wood sill per Figure 5.7 | Steel plate spaced at 4’ o.c. with 4-No. 8 screws and 4-10d or 6-8d common nails | Steel plate spaced at 2’ o.c. with 4-No. 8 screws and 4-10d or 6-8d common nails | Steel plate spaced at 1’ o.c. with 4-No. 8 screws and 4-10d or 6-8d common nails |
| Cantilevered joist to wall track per Figure 5.8 | 1/2" minimum diameter anchor bolt and clip angle spaced at 6’ o.c. with 8- #8 screws | 1/2" minimum diameter anchor bolt and clip angle spaced at 4’ o.c. with 8- #8 screws | 1/2" minimum diameter anchor bolt and clip angle spaced at 2’ o.c. with 8- #8 screws |
For SI:1 inch = 25.4 mm, 1 psf = 0.0479 kN/m2, 1 mph = 1.61 km/hr, 1 foot = 0.3m.
1Use the highest of the wind speed and exposure or the seismic requirements for a given site.
2All screw sizes shown are minimum
Table 5.2
Floor Fastening Schedule1
| Description of Building Elements | Number and Size of Fasteners | Spacing of Fasteners |
| Floor joist to track of an interior load bearing wall per Figures 5.9 and 5.10 | 2 - #8 screws | Each joist |
| Floor joist to track at end of joist | 2- #8 screws | One per flange or two per bearing stiffener |
| Subfloor sheathing to floor joists | #8 screws2 | 6 inches on center on edges and 10 inches on center at intermediate supports |
For SI:1 inch = 25.4 mm
1All screw sizes shown are minimum.
2Head styles shall be bugle-head, flat-head, or similar with a minimum head diameter of 0.29 inch
(7 mm).
Table 5.3
Allowable Spans For Cold-Formed Steel Floor Joists1,2,3,4
Single Span
33 ksi Steel
| Nominal Joist | 30 psf Live Load | 40 psf Live Load | ||||
| Size 5 S | Spacing (inches) | Spacing (inches) | ||||
| 12 | 16 | 24 | 12 | 16 | 24 | |
| 2 x 6 x 33 | 11'-7" | 10'-7" | 9'-1" | 10'-7" | 9'-7" | 8'-1" |
| 2 x 6 x 43 | 12'-8" | 11'-6" | 10'-0" | 11'-6" | 10'-5" | 9'-1" |
| 2 x 6 x 54 | 13'-7" | 12'-4" | 10'-9" | 12'-4" | 11'-2" | 9'-9" |
| 2 x 6 x 68 | 14'-6" | 13'-2" | 11'-6" | 13'-2" | 12'-0" | 10'-6" |
| 2 x 6 x 97 | 16'-1" | 14'-7" | 12'-9" | 14'-7" | 13'-3" | 11'-7" |
| 2 x 8 x 33 | 15'-8" | 13'-3" | 8'-10" | 14'-0" | 10'-7" | 7'-1" |
| 2 x 8 x 43 | 17'-1" | 15'-6" | 13'-7" | 15'-6" | 14'-1" | 12'-3" |
| 2 x 8 x 54 | 18'-4" | 16'-8" | 14'-7" | 16'-8" | 15'-2" | 13'-3" |
| 2 x 8 x 68 | 19'-8" | 17'-11" | 15'-7" | 17'-11" | 16'-3" | 14'-2" |
| 2 x 8 x 97 | 21'-10" | 19'-10" | 17'-4" | 19'-10" | 18'-0" | 15'-9" |
| 2 x 10 x 43 | 20'-6" | 18'-8" | 15'-3" | 18'-8" | 16'-8" | 13'-1" |
| 2 x 10 x 54 | 22'-1" | 20'-1" | 17'-6" | 20'-1" | 18'-3" | 15'-11" |
| 2 x 10 x 68 | 23'-8" | 21'-6" | 18'-10" | 21'-6" | 19'-7" | 17'-1" |
| 2 x 10 x 97 | 26'-4" | 23'-11" | 20'-11" | 23'-11" | 21'-9" | 19'-0" |
| 2 x 12 x 43 | 23'-5" | 20'-3" | 14'-1" | 20'-11" | 16'-10" | 11'-3" |
| 2 x 12 x 54 | 25'-9" | 23'-4" | 19'-7" | 23'-4" | 21'-3" |
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