Section R505 COLD-FORMED STEEL FLOOR FRAMING

Elements shall be straight and free of any defects that would significantly affect structural performance. Cold-formed steel floor framing members shall be in accordance with the requirements of this section.

The provisions of this section shall control the construction of cold-formed steel floor framing for buildings not greater than 60 feet (18 288 mm) in length perpendicular to the joist span, not greater than 40 feet (12 192 mm) in width parallel to the joist span and less than or equal to three stories above grade plane. Cold-formed steel floor framing constructed in accordance with the provisions of this section shall be limited to sites where the ultimate design wind speed is less than 139 miles per hour (62 m/s), Exposure Category B or C, and the ground snow load is less than or equal to 70 pounds per square foot (3.35 kPa).

Where supported by cold-formed steel framed walls in accordance with Section R603, cold-formed steel floor framing shall be constructed with floor joists located in-line with load-bearing studs located below the joists in accordance with Figure R505.1.2 and the tolerances specified as follows:

1. The maximum tolerance shall be ³/₄ inch (19.1 mm) between the centerline of the horizontal framing member and the centerline of the vertical framing member.

2. Where the centerline of the horizontal framing member and bearing stiffener are located to one side of the centerline of the vertical framing member, the maximum tolerance shall be ¹/₈ inch (3 mm) between the web of the horizontal framing member and the edge of the vertical framing member.




FIGURE R505.1.2 IN-LINE FRAMING

Cold-formed steel trusses shall be designed, braced and installed in accordance with AISI S100, Section D4. In the absence of specific bracing requirements, trusses shall be braced in accordance with accepted industry practices, such as the SBCA Cold-Formed Steel Building Component Safety Information (CFSBCSI), Guide to Good Practice for Handling, Installing & Bracing of Cold-Formed Steel Trusses. Truss members shall not be notched, cut or altered in any manner without an approved design.

Load-bearing cold-formed steel floor framing members shall be in accordance with this section.

Load-bearing cold-formed steel framing members shall be cold formed to shape from structural quality sheet steel complying with the requirements of ASTM A1003: Structural Grades 33 Type H and 50 Type H.

Load-bearing cold-formed steel framing shall have a metallic coating complying with ASTM A1003 and one of the following:

1. A minimum of G 60 in accordance with ASTM A653.

2. A minimum of AZ 50 in accordance with ASTM A792.

Load-bearing cold-formed steel floor framing members shall comply with Figure R505.2.3(1) and with the dimensional and thickness requirements specified in Table R505.2.3. Additionally, all C-shaped sections shall have a minimum flange width of 1.625 inches (41 mm) and a maximum flange width of 2 inches (51 mm). The minimum lip size for C-shaped sections shall be ¹/₂ inch (12.7 mm). Track sections shall comply with Figure R505.2.3(2) and shall have a minimum flange width of 1¹/₄ inch (32 mm). Minimum Grade 33 ksi steel shall be used wherever 33 mil and 43 mil thicknesses are specified. Minimum Grade 50 ksi steel shall be used wherever 54 and 68 mil thicknesses are specified.



FIGURE R505.2.3(1) C-SHAPED SECTION



FIGURE R505.2.3(2) TRACK SECTION

TABLE R505.2.3 COLD-FORMED STEEL JOIST SIZES AND THICKNESS

MEMBER DESIGNATIONa	WEB DEPTH (inches)	MINIMUM BASE STEEL THICKNESS mil (inches)
550S162-t	5.5	33 (0.0329), 43 (0.0428), 54 (0.0538), 68 (0.0677)
800S162-t	8	33 (0.0329), 43 (0.0428), 54 (0.0538), 68 (0.0677)
1000S162-t	10	43 (0.0428), 54 (0.0538), 68 (0.0677)
1200S162-t	12	43 (0.0428), 54 (0.0538), 68 (0.0677)

For SI: 1 inch = 25.4 mm, 1 mil = 0.0254 mm.

a. The member designation is defined by the first number representing the member depth in 0.01 inch, the letter "S" representing a stud or joist member, the second number representing the flange width in 0.01 inch, and the letter "t" shall be a number representing the minimum base metal thickness in mils.

Load-bearing cold-formed steel framing members shall have a legible label, stencil, stamp or embossment with the following information as a minimum:

1. Manufacturer's identification.

2. Minimum base steel thickness in inches (mm).

3. Minimum coating designation.

4. Minimum yield strength, in kips per square inch (ksi) (MPa).

Screws for steel-to-steel connections shall be installed with a minimum edge distance and center-to-center spacing of ¹/₂ inch (12.7 mm), shall be self-drilling tapping, and shall conform to ASTM C1513. Floor sheathing shall be attached to cold-formed steel joists with minimum No. 8 self-drilling tapping screws that conform to ASTM C1513. Screws attaching floor sheathing to cold-formed steel joists shall have a minimum head diameter of 0.292 inch (7.4 mm) with countersunk heads and shall be installed with a minimum edge distance of ³/₈ inch (9.5 mm). Gypsum board ceilings shall be attached to cold-formed steel joists with minimum No. 6 screws conforming to ASTM C954 or ASTM C1513 with a bugle head style and shall be installed in accordance with Section R702. For all connections, screws shall extend through the steel a minimum of three exposed threads. All fasteners shall have rust-inhibitive coating suitable for the installation in which they are being used, or be manufactured from material not susceptible to corrosion.

Web holes, web hole reinforcing, and web hole patching shall be in accordance with this section.

Web holes in floor joists shall comply with all of the following conditions:

1. Holes shall conform to Figure R505.2.6.1.

2. Holes shall be permitted only along the centerline of the web of the framing member.

3. Holes shall have a center-to-center spacing of not less than 24 inches (610 mm).

4. Holes shall have a web hole width not greater than 0.5 times the member depth, or 2¹/₂ inches (64.5 mm).

5. Holes shall have a web hole length not exceeding 4¹/₂ inches (114 mm).

6. Holes shall have a minimum distance between the edge of the bearing surface and the edge of the web hole of not less than 10 inches (254 mm).

Framing members with web holes not conforming to the above requirements shall be reinforced in accordance with Section R505.2.6.2, patched in accordance with Section R505.2.6.3 or designed in accordance with accepted engineering practices.




FIGURE R505.2.6.1 FLOOR JOIST WEB HOLES

Reinforcement of web holes in floor joists not conforming to the requirements of Section R505.2.6.1 shall be permitted if the hole is located fully within the center 40 percent of the span and the depth and length of the hole does not exceed 65 percent of the flat width of the web. The reinforcing shall be a steel plate or C-shape section with a hole that does not exceed the web hole size limitations of Section R505.2.6.1 for the member being reinforced. The steel reinforcing shall be the same thickness as the receiving member and shall extend not less than 1 inch (25 mm) beyond all edges of the hole. The steel reinforcing shall be fastened to the web of the receiving member with No. 8 screws spaced not more than 1 inch (25 mm) center-to-center along the edges of the patch with minimum edge distance of ¹/₂ inch (12.7 mm).

Patching of web holes in floor joists not conforming to the requirements in Section R505.2.6.1 shall be permitted in accordance with either of the following methods:

1. Framing members shall be replaced or designed in accordance with accepted engineering practices where web holes exceed the following size limits:

1.1. The depth of the hole, measured across the web, exceeds 70 percent of the flat width of the web.

1.2. The length of the hole, measured along the web, exceeds 10 inches (254 mm) or the depth of the web, whichever is greater.

2. Web holes not exceeding the dimensional requirements in Section R505.2.6.3, Item 1, shall be patched with a solid steel plate, stud section or track section in accordance with Figure R505.2.6.3. The steel patch shall, as a minimum, be of the same thickness as the receiving member and shall extend not less than 1 inch (25 mm) beyond all edges of the hole. The steel patch shall be fastened to the web of the receiving member with No. 8 screws spaced not more than 1 inch (25 mm) center-to-center along the edges of the patch with minimum edge distance of ¹/₂ inch (12.7 mm).




FIGURE R505.2.6.3 FLOOR JOIST WEB HOLE PATCH

Cold-formed steel floors shall be constructed in accordance with this section.

Cold-formed steel framed floors shall be anchored to foundations, wood sills or load-bearing walls in accordance with Table R505.3.1(1) and Figure R505.3.1(1), R505.3.1(2), R505.3.1(3), R505.3.1(4), R505.3.1(5) or R505.3.1(6). Anchor bolts shall be located not more than 12 inches (305 mm) from corners or the termination of bottom tracks. Continuous cold-formed steel joists supported by interior load-bearing walls shall be constructed in accordance with Figure R505.3.1(7). Lapped cold-formed steel joists shall be constructed in accordance with Figure R505.3.1(8). End floor joists constructed on foundation walls parallel to the joist span shall be doubled unless a C-shaped bearing stiffener, sized in accordance with Section R505.3.4, is installed web-to-web with the floor joist beneath each supported wall stud, as shown in Figure R505.3.1(9). Fastening of cold-formed steel joists to other framing members shall be in accordance with Section R505.2.5 and Table R505.3.1(2).

TABLE R505.3.1(1) FLOOR TO FOUNDATION OR BEARING WALL CONNECTION REQUIREMENTS^{a, b}

FRAMING CONDITION	BASIC ULTIMATE WIND SPEED (mph) AND EXPOSURE
	110 mph Exposure Category C or less than 139 mph Exposure Category B	Less than 139 mph Exposure Category C
Floor joist to wall track of exterior wall in accordance with Figure R505.3.1(1)	2-No. 8 screws	3-No. 8 screws
Rim track or end joist to load-bearing wall top track in accordance with Figure R505.3.1(1)	1-No. 8 screw at 24 inches o.c.	1-No. 8 screw at 24 inches o.c.
Rim track or end joist to wood sill in accordance with Figure R505.3.1(2)	Steel plate spaced at 4 feet o.c. with 4-No. 8 screws and 4-10d or 6-8d common nails	Steel plate spaced at 2 feet o.c. with 4-No. 8 screws and 4-10d or 6-8d common nails
Rim track or end joist to foundation in accordance with Figure R505.3.1(3)	1/2 inch minimum diameter anchor bolt and clip angle spaced at 6 feet o.c. with 8-No. 8 screws	1/2 inch minimum diameter anchor bolt and clip angle spaced at 4 feet o.c. with 8-No. 8 screws
Cantilevered joist to foundation in accordance with Figure R505.3.1(4)	1/2 inch minimum diameter anchor bolt and clip angle spaced at 6 feet o.c. with 8-No. 8 screws	1/2 inch minimum diameter anchor bolt and clip angle spaced at 4 feet o.c. with 8-No. 8 screws
Cantilevered joist to wood sill in accordance with Figure R505.3.1(5)	Steel plate spaced at 4 feet o.c. with 4-No. 8 screws and 4-10d or 6-8d common nails	Steel plate spaced at 2 feet o.c. with 4-No. 8 screws and 4-10d or 6-8d common nails
Cantilevered joist to exterior load-bearing wall track in accordance with Figure R505.3.1(6)	2-No. 8 screws	3-No. 8 screws

For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kPa, 1 mile per hour = 0.447 m/s, 1 foot = 304.8 mm.

a. Anchor bolts are to be located not more than 12 inches from corners or the termination of bottom tracks such as at door openings or corners. Bolts extend a minimum of 15 inches into masonry or 7 inches into concrete. Anchor bolts connecting cold-formed steel framing to the foundation structure are to be installed so that the distance from the center of the bolt hole to the edge of the connected member is not less than one and one-half bolt diameters.

b. All screw sizes shown are minimum.

TABLE R505.3.1(2) FLOOR FASTENING SCHEDULE^a

DESCRIPTION OF BUILDING ELEMENTS	NUMBER AND SIZE OF FASTENERS	SPACING OF FASTENERS
Floor joist to track of an interior load-bearing wall in accordance with Figures R505.3.1(7) and R505.3.1(8)	2 No. 8 screws	Each joist
Floor joist to track at end of joist	2 No. 8 screws	One per flange or two per bearing stiffener
Subfloor to floor joists	No. 8 screws	6 in. o.c. on edges and 12 in. o.c. at intermediate supports

For SI: 1 inch = 25.4 mm.

a. All screw sizes shown are minimum.

FIGURE 505.3.1(1) FLOOR TO EXTERIOR LOAD-BEARING WALL STUD CONNECTION




FIGURE R505.3.1(2) FLOOR TO WOOD SILL CONNECTION




FIGURE R505.3.1(3) FLOOR TO FOUNDATION CONNECTION




FIGURE R505.3.1(4) CANTILEVERED FLOOR TO FOUNDATION CONNECTION




FIGURE R505.3.1(5) CANTILEVERED FLOOR TO WOOD SILL CONNECTION




FIGURE R505.3.1(6) CANTILEVERED FLOOR TO EXTERIOR LOAD-BEARING WALL CONNECTION




FIGURE R505.3.1(7) CONTINUOUS SPAN JOIST SUPPORTED ON INTERIOR LOAD-BEARING WALL




FIGURE R505.3.1(8) LAPPED JOISTS SUPPORTED ON INTERIOR LOAD-BEARING WALL



FIGURE R505.3.1(9) BEARING STIFFENERS FOR END JOISTS

Floor joist size and thickness shall be determined in accordance with the limits set forth in Table R505.3.2 for single or continuous spans. Where continuous joist members are used, the interior bearing supports shall be located within 2 feet (610 mm) of midspan of the cold-formed steel joists, and the individual spans shall not exceed the spans in Table R505.3.2. Floor joists shall have a bearing support length of not less than 1¹/₂ inches (38 mm) for exterior wall supports and 3¹/₂ inches (89 mm) for interior wall supports. Tracks shall be not less than 33 mils (0.84 mm) thick except when used as part of a floor header or trimmer in accordance with Section R505.3.8. Bearing stiffeners shall be installed in accordance with Section R505.3.4.

TABLE R505.3.2 ALLOWABLE SPANS FOR COLD-FORMED STEEL JOISTS‒SINGLE OR CONTINUOUS SPANS^{a, b, c, d, e}

JOIST DESIGNATION	30 PSF LIVE LOAD				40 PSF LIVE LOAD
	Spacing (inches)				Spacing (inches)
	12	16	19.2	24	12	16	19.2	24
550S162-33	11'-7″	10'-7″	9'-6″	8'-6″	10'-7″	9'-3″	8'-6″	7'-6″
550S162-43	12'-8″	11'-6″	10'-10″	10'-2″	11'-6″	10'-5″	9'-10″	9'-1″
550S162-54	13'-7″	12'-4″	11'-7″	10'-9″	12'-4″	11'-2″	10'-6″	9'-9″
550S162-68	14'-7″	13'-3″	12'-6″	11'-7″	13'-3″	12'-0″	11'-4″	10'-6″
800S162-33	15'-8″	13'-11″	12'-9″	11'-5″	14'-3″	12'-5″	11'-3″	9'-0″
800S162-43	17'-1″	15'-6″	14'-7″	13'-7″	15'-6″	14'-1″	13'-3″	12'-4″
800S162-54	18'-4″	16'-8″	15'-8″	14'-7″	16'-8″	15'-2″	14'-3″	13'-3″
800S162-68	19'-9″	17'-11″	16'-10″	15'-8″	17'-11″	16'-3″	15'-4″	14'-2″
1000S162-43	20'-6″	18'-8″	17'-6″	15'-8″	18'-8″	16'-11″	15'-6″	13'-11″
1000S162-54	22'-1″	20'-0″	18'-10″	17'-6″	20'-0″	18'-2″	17'-2″	15'-11″
1000S162-68	23'-9″	21'-7″	20'-3″	18'-10″	21'-7″	19'-7″	18'-5″	17'-1″
1200S162-43	23'-9″	20'-10″	19'-0″	16'-8″	21'-5″	18'-6″	16'-6″	13'-2″
1200S162-54	25'-9″	23'-4″	22'-0″	20'-1″	23'-4″	21'-3″	20'-0″	17'-10″
1200S162-68	27'-8″	25'-1″	23'-8″	21'-11″	25'-1″	22'-10″	21'-6″	21'-1″

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 mil = 0.0254 mm.

a. Deflection criteria: L/480 for live loads, L/240 for total loads.

b. Floor dead load = 10 psf.

c. Table provides the maximum clear span in feet and inches.

d. Bearing stiffeners are to be installed at all support points and concentrated loads.

e. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thickness. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thickness.

Joist bracing and blocking shall be in accordance with this section.

The top flanges of cold-formed steel joists shall be laterally braced by the application of floor sheathing fastened to the joists in accordance with Section R505.2.5 and Table R505.3.1(2).

Floor joists with spans that exceed 12 feet (3658 mm) shall have the bottom flanges laterally braced in accordance with one of the following:

1. Gypsum board installed with minimum No. 6 screws in accordance with Section R702.

2. Continuous steel straps installed in accordance with Figure R505.3.3.2(1). Steel straps shall be spaced at a maximum of 12 feet (3658 mm) on center and shall be at least 1¹/₂ 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 one No. 8 screw, fastened to blocking with two No. 8 screws, and fastened at each end (of strap) with two No. 8 screws. Blocking in accordance with Figure R505.3.3.2(1) or R505.3.3.2(2) shall be installed between joists at each end of the continuous strapping and at a maximum spacing of 12 feet (3658 mm) measured along the continuous strapping (perpendicular to the joist run). Blocking shall also be located at the termination of all straps. As an alternative to blocking at the ends, anchoring the strap to a stable building component with two No. 8 screws shall be permitted.




FIGURE R505.3.3.2(1) JOIST BLOCKING (SOLID)




FIGURE R505.3.3.2(2) JOIST BLOCKING (STRAP)

Blocking is not required for continuous back-to-back floor joists at bearing supports. Blocking shall be installed between every other joist for single continuous floor joists across bearing supports in accordance with Figure R505.3.1(7). Blocking shall consist of C-shape or track section with a minimum thickness of 33 mils (0.84 mm). Blocking shall be fastened to each adjacent joist through a 33-mil (0.84 mm) clip angle, bent web of blocking or flanges of web stiffeners with two No. 8 screws on each side. The minimum depth of the blocking shall be equal to the depth of the joist minus 2 inches (51 mm). The minimum length of the angle shall be equal to the depth of the joist minus 2 inches (51 mm).

Blocking shall be installed between every other joist over cantilever bearing supports in accordance with Figure R505.3.1(4), R505.3.1(5) or R505.3.1(6). Blocking shall consist of C-shape or track section with minimum thickness of 33 mils (0.84 mm). Blocking shall be fastened to each adjacent joist through bent web of blocking, 33 mil clip angle or flange of web stiffener with two No. 8 screws at each end. The depth of the blocking shall be equal to the depth of the joist. The minimum length of the angle shall be equal to the depth of the joist minus 2 inches (51 mm). Blocking shall be fastened through the floor sheathing and to the support with three No. 8 screws (top and bottom).

Bearing stiffeners shall be installed at each joist bearing location in accordance with this section, except for joists lapped over an interior support not carrying a load-bearing wall above. Floor joists supporting jamb studs with multiple members shall have two bearing stiffeners in accordance with Figure R505.3.4(1). Bearing stiffeners shall be fabricated from a C-shaped, track or clip angle member in accordance with the one of following:

1. C-shaped bearing stiffeners:

1.1. Where the joist is not carrying a load-bearing wall above, the bearing stiffener shall be a minimum 33 mil (0.84 mm) thickness.

1.2. Where the joist is carrying a load-bearing wall above, the bearing stiffener shall be not less than the same designation thickness as the wall stud above.

2. Track bearing stiffeners:

2.1. Where the joist is not carrying a load-bearing wall above, the bearing stiffener shall be a minimum 43 mil (1.09 mm) thickness.

2.2. Where the joist is carrying a load-bearing wall above, the bearing stiffener shall be not less than one designation thickness greater than the wall stud above.

The minimum length of a bearing stiffener shall be the depth of member being stiffened minus ³/₈ inch (9.5 mm). Each bearing stiffener shall be fastened to the web of the member it is stiffening as shown in Figure R505.3.4(2).



FIGURE R505.3.4(1) BEARING STIFFENERS UNDER JAMB STUDS




FIGURE R505.3.4(2) BEARING STIFFENER

Flanges and lips of load-bearing cold-formed steel floor framing members shall not be cut or notched.

Floor cantilevers for the top floor of a two- or three-story building or the first floor of a one-story building shall not exceed 24 inches (610 mm). Cantilevers, not exceeding 24 inches (610 mm) and supporting two stories 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 not less than 6 feet (1829 mm) toward the inside and shall be fastened with not less than two No. 8 screws spaced at 24 inches (610 mm) on center through the webs (for back-to-back) or flanges (for nested joists).

Joists and other structural members shall not be spliced. Splicing of tracks shall conform to Figure R505.3.7.




FIGURE R505.3.7 TRACK SPLICE

Openings in floors shall be framed with header and trimmer joists. Header joist spans shall not exceed 6 feet (1829 mm) or 8 feet (2438 mm) in length in accordance with Figure R505.3.8(1) or R505.3.8(2), respectively. Header and trimmer joists shall be fabricated from joist and track members, having a minimum size and thickness at least equivalent to the adjacent floor joists, and shall be installed in accordance with Figures R505.3.8(1), R505.3.8(2), R505.3.8(3) and R505.3.8(4). Each header joist shall be connected to trimmer joists with four 2-inch by 2-inch (51-mm by 51-mm) clip angles. Each clip angle shall be fastened to both the header and trimmer joists with four No. 8 screws, evenly spaced, through each leg of the clip angle. The clip angles shall have a thickness not less than that of the floor joist. Each track section for a built-up header or trimmer joist shall extend the full length of the joist (continuous).




FIGURE R505.3.8(1) COLD-FORMED STEEL FLOOR CONSTRUCTION‒6-FOOT FLOOR OPENING




FIGURE R505.3.8(2) COLD-FORMED STEEL FLOOR CONSTRUCTION‒8-FOOT FLOOR OPENING




FIGURE R505.3.8(3) COLD-FORMED STEEL FLOOR CONSTRUCTION: FLOOR HEADER TO TRIMMER CONNECTION‒6-FOOT OPENING




FIGURE R505.3.8(4) COLD-FORMED STEEL FLOOR CONSTRUCTION: FLOOR HEADER TO TRIMMER CONNECTION‒8-FOOT OPENING