Section R505 Cold-Formed Steel Floor Framing
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:
- 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 mm) between the web of the horizontal framing member and the edge of the vertical framing member.
For SI: 1 inch = 25.4 mm.
IN-LINE FRAMING
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.
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.
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.
- 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.
FIGURE R505.2.3(1)
C-SHAPED SECTION
TRACK SECTION
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).
Web holes in floor joists shall comply with all of the following conditions:
- Holes shall conform to Figure R505.2.6.1.
- Holes shall be permitted only along the centerline of the web of the framing member.
- Holes shall have a center-to-center spacing of not less than 24 inches (610 mm).
- Holes shall have a web hole width not greater than 0.5 times the member depth, or 21/2 inches (64.5 mm).
- Holes shall have a web hole length not exceeding 41/2 inches (114 mm).
- 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 these 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.
For SI: 1 inch = 25.4 mm.
FLOOR JOIST WEB HOLES
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:
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.
- 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).
For SI: 1 inch = 25.4 mm.
FLOOR JOIST WEB HOLE PATCH