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// CODE SNIPPET

Section R505 Cold-Formed Steel Floor Framing

2015 Michigan Residential Code > 5 Floors > R505 Cold-Formed Steel Floor Framing
JUMP TO FULL CODE CHAPTER

R505.1 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.

R505.1.1 Applicability Limits

The provisions of this section shall control the construction of cold-formed steel floor framing for buildings not greater than 60 feet (18288 mm) in length perpendicular to the joist span, not greater than 40 feet (12192 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).

R505.1.2 In-Line 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:
  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.


For SI: 1 inch = 25.4 mm.
FIGURE R505.1.2
IN-LINE FRAMING

R505.1.3 Floor Trusses

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.

R505.2 Structural Framing

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

R505.2.1 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.

R505.2.2 Corrosion Protection

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.

R505.2.3 Dimension, Thickness and Material Grade

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.
  1. 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.

R505.2.4 Identification

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

R505.2.5 Fastening

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.

R505.2.6 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.

R505.2.6.1 Web Holes

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.


For SI: 1 inch= 25.4 mm.
FIGURE R505.2.6.1
FLOOR JOIST WEB HOLES

R505.2.6.2 Web Hole Reinforcing

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).

R505.2.6.3 Hole Patching

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

For SI: 1 inch= 25.4 mm.
FIGURE R505.2.6.3
FLOOR JOIST WEB HOLE PATCH

R505.3 Floor Construction

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

Related Code Sections


R505.1 Floors, 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 ...
2015 Michigan Residential Code > 5 Floors > R505 Cold-Formed Steel Floor Framing > R505.1 Cold-Formed Steel Floor Framing
R505.3.6 Floors, Floor Cantilevers
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 ...
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R505.3.5 Floors, Cutting and Notching
Flanges and lips of load-bearing cold-formed steel floor framing members shall not be cut or notched ...
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R505.3.1 Floors, Floor to Foundation or Load-Bearing Wall Connections
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 ...
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R505.3.2 Floors, Minimum Floor Joist Sizes
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 ...
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