Structural Steel (C-51) · Lesson 1 of 6

Reading Steel Callouts, Substitutions, and Material Identity

"Reading Steel Callouts, Substitutions, and Material Identity" is lesson 1 of 6 in the Structural Steel (C-51) Learning Hub. It opens with "A Callout Is a Recipe, Not a Name" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. A Callout Is a Recipe, Not a Name
  2. Weights Are Nominal Weights
  3. A Substitution Is Written Permission, Not a Shop Habit
  4. The Material Grade Rides with the Shape
  5. Special Inspection Follows the Steel

The worked example in the course applies this lesson to a realistic job in 6 steps, from "Decode the mark" through "Is the swap allowed?".

What you'll be able to do

  • Explain the main idea of "Reading Steel Callouts, Substitutions, and Material Identity" in plain language you can use on the exam.
  • Apply this step with confidence: "A Substitution Is Written Permission, Not a Shop Habit".
  • Apply this step with confidence: "The Material Grade Rides with the Shape".
  • Apply this step with confidence: "Special Inspection Follows the Steel".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Reading a Steel Callout and What the CA Books PrintCALLOUT ON THE PLANW6 x 9 x 6'-0" POST6 innominal depthW = wide flange9 lb of steel in every foot of length6 ft post: 9 x 6 = 54 lbReading order is drafting conventionWHAT THE CA BOOKS PRINTStd Specs 83-2.01A(2)A W6 x 8.5 post may replace a W6 x 9 postStd Specs 55-1.04Weight: nominal, no deduction for holesStd Specs 55-1.02D(3)Default plates, shapes, bars: ASTM A709 Gr 50Std Specs 55-1.02D(3)Swap: depth, width, thickness not less2025 CBC 2201.2Grade not identifiable? Test itAs drawn: 24 x 54 = 1,296 lb | W6 x 8.5: 24 x 51 = 1,224 lbPrinted swap saves 72 lb: 1,296 - 1,224 = 72 lbSources: Caltrans Std Plan A77N2; Std Specs 83-2.01A(2), 55-1.04, 55-1.02D(3); 2025 CBC 2201.2CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: A Callout Is a Recipe, Not a Name

One place the California books print a structural shape callout is Caltrans Standard Plan A77N2, which labels a guardrail line post W6 x 9 x 6'-0" POST. Read it left to right: the letter is the shape family (W = wide flange), the first number is the nominal depth in inches (6), the second is the weight in pounds per linear foot (9), and the last is the length (6'-0"). That reading order is a drafting convention; no California code section defines it, and the shape tables themselves are in the AISC Manual, which is not a California code book. The weight per foot is the number that drives freight, the crane pick and the bid, so read it first. Source: 2025 Caltrans Standard Plans, Plan A77N2 (Standard Plans text, page 107); reading order is convention.

Step 2: Weights Are Nominal Weights

When the State pays for structural steel it pays by weight, and the rule is printed: the weight of rolled shapes and structural plate is computed using nominal weight and dimensions with no deduction for copes, cuts, and holes. So a 9 lb/ft callout is taken as 9 lb every foot, even where the shop coped the ends or punched bolt holes. Use the same habit in your own takeoff. Source: 2025 Caltrans Standard Specifications, Section 55-1.04, item 2 (Std Specs text, page 908).

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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