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Section R804 Cold-Formed Steel Roof Framing

Residential Code 2018 of Kansas > 8 Roof-Ceiling Construction > R804 Cold-Formed Steel Roof Framing

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R804.1 General

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

R804.1.1 Applicability Limits

The provisions of this section shall control the construction of cold-formed steel roof framing for buildings not greater than 60 feet (18 288 mm) perpendicular to the joist, rafter or truss span, not greater than 40 feet (12 192 mm) in width parallel to the joist span or truss, less than or equal to three stories above grade plane and with roof slopes not less than 3:12 (25-percent slope) or greater than 12:12 (100-percent slope). Cold-formed steel roof framing constructed in accordance with the provisions of this section shall be limited to sites where the ultimate design wind speed is less than 140 miles per hour (63 m/s), Exposure Category B or C, and the ground snow load is less than or equal to 70 pounds per square foot (3350 Pa).

R804.1.2 In-Line Framing

Cold-formed steel roof framing constructed in accordance with Section R804 shall be located in line with load-bearing studs in accordance with Figure R804.1.2 and the tolerances specified as follows:

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.
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 (3.2 mm) between the web of the horizontal framing member and the edge of the vertical framing member.

For SI: 1 inch = 25.4 mm.
FIGURE R804.1.2
IN-LINE FRAMING

R804.2 Structural Framing

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

R804.2.1 Material

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.

R804.2.2 Corrosion Protection

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

Not less than G 60 in accordance with ASTM A653.
Not less than AZ 50 in accordance with ASTM A792.

R804.2.3 Dimension, Thickness and Material Grade

Load-bearing, cold-formed steel roof framing members shall comply with Figure R804.2.3(1) and with the dimensional and thickness requirements specified in Table R804.2.3. Additionally, 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). Tracks shall comply with Figure R804.2.3(2) and shall have a minimum flange width of 1¹/₄ inches (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.

TABLE R804.2.3

LOAD-BEARING COLD-FORMED STEEL ROOF FRAMING MEMBER SIZES AND THICKNESSES

MEMBER DESIGNATION^a	WEB DEPTH (inches)	MINIMUM BASE STEEL THICKNESS mil (inches)
350S162-t	3.5	33 (0.0329), 43 (0.0428), 54 (0.0538)
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

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

R804.2.4 Identification

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

Manufacturer's identification.
Minimum base steel thickness in inches (mm).
Minimum coating designation.
Minimum yield strength, in kips per square inch (ksi) (MPa).

R804.2.5 Fastening Requirements

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. Structural sheathing shall be attached to cold-formed steel roof rafters with minimum No. 8 self-drilling tapping screws that conform to ASTM C1513. Screws for attaching structural sheathing to cold-formed steel roof framing 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 R805. For all connections, screws shall extend through the steel not fewer than three exposed threads. 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.

R804.2.6 Web Holes, Web Hole Reinforcing and Web Hole Patching

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

R804.2.6.1 Web Holes

Web holes in roof framing members shall comply with all of the following conditions:

Holes shall conform to Figure R804.2.6.1.
Holes shall be permitted only along the centerline of the web of the framing member.
Center-to-center spacing of holes shall be not less than 24 inches (610 mm).
The web hole width shall be not greater than one-half the member depth, or 2¹/₂ inches (64 mm).
Holes shall have a web hole length not exceeding 4¹/₂ inches (114 mm).
The minimum distance between the edge of the bearing surface and the edge of the web hole shall be not less than 10 inches (254 mm).

Framing members with web holes not conforming to Items 1 though 6 shall be reinforced in accordance with Section R804.2.6.2, patched in accordance with Section R804.2.6.3 or designed in accordance with accepted engineering practices.

For SI: 1 inch = 25.4 mm.
FIGURE R804.2.6.1
ROOF FRAMING MEMBER WEB HOLES

R804.2.6.2 Web Hole Reinforcing

Reinforcement of web holes in ceiling joists not conforming to the requirements of Section R804.2.6.1 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 do not exceed 65 percent of the flat width of the web. The reinforcing shall be a steel plate or C-shaped section with a hole that does not exceed the web hole size limitations of Section R804.2.6.1 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 greater 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).

R804.2.6.3 Hole Patching

Patching of web holes in roof framing members not conforming to the requirements in Section R804.2.6.1 shall be permitted in accordance with either of the following methods:

Framing members shall be replaced or designed in accordance with accepted engineering practices where web holes exceed either of the following size limits:
1. 1.1. The depth of the hole, measured across the web, exceeds 70 percent of the flat width of the web.
2. 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.
Web holes not exceeding the dimensional requirements in Section R804.2.6.3, Item 1, shall be patched with a solid steel plate, stud section or track section in accordance with Figure R804.2.6.3. The steel patch shall, as a minimum, 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 patch shall be fastened to the web of the receiving member with No. 8 screws spaced not greater 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).

For SI: 1 inch = 25.4 mm.
FIGURE R804.2.6.3
ROOF FRAMING MEMBER WEB HOLE PATCH

R804.3 Roof Construction

Cold-formed steel roof systems constructed in accordance with the provisions of this section shall consist of both ceiling joists and rafters in accordance with Figure R804.3 and fastened in accordance with Table R804.3.

FIGURE R804.3
COLD-FORMED STEEL ROOF CONSTRUCTION

TABLE R804.3
ROOF FRAMING FASTENING SCHEDULE^{a, b}
DESCRIPTION OF BUILDING ELEMENTS			NUMBER AND SIZE OF FASTENERS^a				SPACING OF FASTENERS
Roof sheathing (oriented strand board or plywood) to rafter			No. 8 screws				6" o.c. on edges and 12" o.c. at interior supports. 6" o.c. at gable end truss
Gable end truss to endwall top track			No. 10 screws				12" o.c.
Rafter to ceiling joist			Minimum No. 10 screws, in accordance with Table R804.3.1.1(3)				Evenly spaced, not less than ¹/₂" from all edges.
Ceiling joist or roof truss to top track of bearing wall^b	Ceiling Joist Spacing (in.)	Roof Span (ft)	Ultimate Design Wind Speed (mph) and Exposure Category				Each ceiling joist or roof truss
	Ceiling Joist Spacing (in.)	Roof Span (ft)	126 B 110 C	<139 B 115 C	126 C	<139 C
	16	24	2	2	2	3
		28	2	2	3	3
		32	2	2	3	4
		36	2	2	3	4
		40	2	2	3	4
	24	24	2	2	3	4
		28	2	2	4	5
		32	2	3	4	5
		36	2	3	4	6
		40	2	3	5	6

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.

Screws are a minimum No. 10 unless noted otherwise.
Indicated number of screws shall be applied through the flanges of the truss or ceiling joist or through each leg of a 54 mil clip angle. See Section R804.3.8 for additional requirements to resist uplift forces.