Drywall (C-9) · Lesson 1 of 5

Steel Framing Thickness and Screw Selection for Board

"Steel Framing Thickness and Screw Selection for Board" is lesson 1 of 5 in the Drywall (C-9) Learning Hub. It opens with "Steel Thickness Is Printed Two Ways" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. Steel Thickness Is Printed Two Ways
  2. What the Code Says About the Framing Itself
  3. The 0.033 in. Line in the Screw Rule
  4. Turn the Rule Into a Screw Length
  5. On Some Walls the Board Is Doing Structural Work

The worked example in the course applies this lesson to a realistic job in 6 steps, from "Find the thickness band" through "Sheets and total".

What you'll be able to do

  • Explain the main idea of "Steel Framing Thickness and Screw Selection for Board" in plain language you can use on the exam.
  • Apply this step with confidence: "The 0.033 in. Line in the Screw Rule".
  • Apply this step with confidence: "Turn the Rule Into a Screw Length".
  • Apply this step with confidence: "On Some Walls the Board Is Doing Structural Work".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Steel Thickness Sets the Screw RuleSCREW RULE BY STEEL THICKNESS (R702.3.5.1)Steel thicknessScrew requirementUnder 0.033 in.(e.g. 0.018 in.)Type S (ASTM C1002) or bugle(C1513); 3/8 in. into the steel0.033 to 0.112 in.(33 mils and thicker)ASTM C954 or bugle (C1513)All steel framingNo. 6 screw minimumSECTION: 5/8 in. BOARD ON 0.018 in. STEEL5/8 in. board3/8 in. into steelSteel flange (not to scale)Length = 5/8 + 3/8 = 1 in.24 ft x 9 ft wall, Item 13-1.1 build0.018 in. studs 24 in. o.c.; 5/8 in. Type Xeach side; 4 x 9 ft sheets hung verticalLength: 5/8 + 3/8 = 1 in. No. 6 screwSchedule: 8 in. perimeter, 12 in. middle studSheets: 216 / 36 = 6 per side, 12 in allSCREWS PER 4 x 9 SHEETPerimeter: 2 x (108 + 48) = 312 in.312 / 8 = 39 screwsMiddle stud: 108 / 12 = 9 spaces9 - 1 = 8 screws (ends counted above)39 + 8 = 47 per sheet; 12 x 47 = 5641 in. No. 6 Type S or bugle screws: 47 per 4 x 9 sheet, 564 for the wallSources: 2025 CRC R702.3.5.1 and R603.2.5; 2025 CBC Table 721.1(2) Item 13-1.1.The closed-loop perimeter count is an estimating method, not a code value.CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: Steel Thickness Is Printed Two Ways

California's books give steel framing thickness two ways. The 2025 CBC prescriptive wall assemblies in Table 721.1(2) print decimal inches with a sheet-steel gage number: 0.018 in. (No. 25 gage) channel studs in Items 13-1.1 and 13-1.2, and 0.055 in. (No. 16 gage) nailable studs in Item 13-1.3. The 2025 CRC steel-framing tables (Section R603) print thickness in mils, such as 33 and 43, with the footnote 1 mil = 0.0254 mm. A mil is 1/1000 in., so 33 mils is 0.033 in. (the CRC pairs 33 mils with 0.84 mm). Read each book in its own unit.

Step 2: What the Code Says About the Framing Itself

2025 CRC R702.3.3 requires cold-formed steel framing that supports gypsum board to be not less than 1-1/4 in. wide in its least dimension. Nonload-bearing steel framing must comply with AISI S220 and load-bearing steel framing with AISI S240. 2025 CBC Table 2506.2 lists the same two: AISI S220 for nonstructural studs and track, AISI S240 for structural. The schedule on the plans tells you which one you are hanging board on.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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