- 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 center line 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.
Load-bearing, cold-formed steel roof framing members shall comply with Figure R804.2(1) and with the dimensional and minimum thickness requirements specified in Tables R804.2(1) and R804.2(2). Tracks shall comply with Figure R804.2(2) and shall have a minimum flange width of 11/4 inches (32 mm).
LOAD-BEARING COLD-FORMED STEEL MEMBER SIZES
|NOMINAL MEMBER SIZE |
|WEB DEPTH |
|MINIMUM FLANGE WIDTH |
|MAXIMUM FLANGE WIDTH |
|MINIMUM LIP SIZE |
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 [see Table R804.2(2)].
MINIMUM THICKNESS OF COLD-FORMED STEEL MEMBERS
|DESIGNATION THICKNESS (mils)||MINIMUM BASE STEEL THICKNESS (inch)|
For SI: 1 inch = 25.4 mm, 1 mil = 0.0254 mm.
Load-bearing, cold-formed steel framing members shall be cold-formed to shape from structural quality sheet steel complying with the requirements of one of the following:
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).
Load-bearing, cold-formed steel framing shall have a metallic coating complying with ASTM A 1003 and one of the following:
- A minimum of G 60 in accordance with ASTM A 653.
- A minimum of AZ 50 in accordance with ASTM A 792.
Screws for steel-to-steel connections shall be installed with a minimum edge distance and center-to-center spacing of 1/2 inch (13 mm), shall be self-drilling tapping, and shall conform to ASTM C 1513. Structural sheathing shall be attached to cold-formed steel roof rafters with minimum No. 8 self-drilling tapping screws that conform to ASTM C 1513. 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 (10 mm). Gypsum board ceilings shall be attached to cold-formed steel joists with minimum No. 6 screws conforming to ASTM C 954 or ASTM C 1513 with a bugle-head style and shall be installed in accordance with Section R805. 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.
Where No. 8 screws are specified in a steel-to-steel connection, reduction of the required number of screws in the connection is permitted in accordance with the reduction factors in Table R804.2.4 when larger screws are used or when one of the sheets of steel being connected is thicker than 33 mils (0.84 mm). When applying the reduction factor, the resulting number of screws shall be rounded up.
SCREW SUBSTITUTION FACTOR
|SCREW SIZE||THINNEST CONNECTED STEEL SHEET (mils)|
For SI: 1 mil = 0.0254 mm.
Web holes in roof framing members shall comply with all of the following conditions:
- Holes shall conform to Figure R804.2.5.1;
- Holes shall be permitted only along the centerline of the web of the framing member;
- Center-to-center spacing of holes shall not be less than 24 inches (610 mm);
- The web hole width shall not be greater than one-half the member depth, or 21/2 inches (64.5 mm);
- Holes shall have a web hole length not exceeding 41/2 inches (114 mm); and
- The minimum distance between the edge of the bearing surface and the edge of the web hole shall not be less than 10 inches (254 mm).
Framing members with web holes not conforming to the above requirements shall be reinforced in accordance with Section R804.2.5.2, patched in accordance with Section R804.2.5.3 or designed in accordance with accepted engineering practices.
Patching of web holes in roof framing members not conforming to the requirements in Section R804.2.5.1 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 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; or
- 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 R804.2.5.3, Item 1, shall be patched with a solid steel plate, stud section or track section in accordance with Figure R804.2.5.3. The steel patch shall, as a minimum, be the same thickness as the receiving member and shall extend at least 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 no greater than 1 inch (25 mm) center-to-center along the edges of the patch with minimum edge distance of 1/2 inch (13 mm).
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, and hip framing in accordance with Section R804.3.3.
ROOF FRAMING FASTENING SCHEDULEa, b
|DESCRIPTION OF BUILDING ELEMENTS||NUMBER AND SIZE OF FASTENERS||SPACING OF FASTENERS|
|Ceiling joist to top track of load-bearing wall||2 No. 10 screws||Each joist|
|Roof sheathing (oriented strand board or ply- |
wood) to rafter
|No. 8 screws||6" o.c. on edges and 12" o.c. at interior |
supports. 6" o.c. at gable end truss
|Truss to bearing walla||2 No. 10 screws||Each truss|
|Gable end truss to end wall top track||No. 10 screws||12" o.c.|
|Rafter to ceiling joist||Minimum No. 10 screws,||Evenly spaced, not less than 1/2" from all edges|
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 shall be applied through the flanges of the truss or ceiling joist or a 54-mil clip angle shall be used with two No. 10 screws in each leg. See Section R804.3.9 for additional requirements to resist uplift forces.
- Spacing of fasteners on roof sheathing panel edges applies to panel edges supported by framing members and at all roof plane perimeters. Blocking of roof sheathing panel edges perpendicular to the framing members shall not be required except at the intersection of adjacent roof planes. Roof perimeter shall be supported by framing members or cold-formed blocking of the same depth and gage as the floor members.