Reinforcing Steel (C-50) · Lesson 5 of 7

Minimum Bars in Footings and Plain Concrete Walls: Checking Bar Area

"Minimum Bars in Footings and Plain Concrete Walls: Checking Bar Area" is lesson 5 of 7 in the Reinforcing Steel (C-50) Learning Hub. It opens with "What the CBC Prints for Plain Concrete Footings" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. What the CBC Prints for Plain Concrete Footings
  2. Get the Bar Area From the Printed Diameter
  3. Footings in Seismic Design Categories D0, D1 and D2 (2025 CRC R403.1.3)
  4. Plain Concrete Walls: Corner, Opening and Spacing Bars (CBC 1905.5.1)
  5. Where It Stops: Footings in SDC A and B and Exceptions

The worked example in the course applies this lesson to a realistic job in 4 steps, from "Required area" through "Thickness rule".

What you'll be able to do

  • Explain the main idea of "Minimum Bars in Footings and Plain Concrete Walls: Checking Bar Area" in plain language you can use on the exam.
  • Apply this step with confidence: "Footings in Seismic Design Categories D0, D1 and D2 (2025 CRC R403.1.3)".
  • Apply this step with confidence: "Plain Concrete Walls: Corner, Opening and Spacing Bars (CBC 1905.5.1)".
  • Apply this step with confidence: "Where It Stops: Footings in SDC A and B and Exceptions".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
MINIMUM BARS IN A PLAIN CONCRETE FOOTING2025 CBC Sec. 1905.6.2 item 3 | 2025 CRC R403.1.3.3 | bar diameters: Caltrans Sec. 52-1.04PLAIN FOOTING, 18" x 12"wall above18"12"top #5bottom #5Two continuous #5 bars, one near the top and one near the bottom.BAR AREA FROM DIAMETERBardb, in.area, sq in.#30.3750.110#40.5000.196#50.6250.307#60.7500.442#70.8750.601#81.0000.785area = 0.7854 x db x db (db: Caltrans 52-1.04)1Gross area = 18 x 12 = 216 sq in.; required steel = 0.002 x 216 = 0.432 sq in.2Two #4: 2 x 0.196 = 0.393 sq in., less than 0.432 - NO. Three #4 = 0.589 OK3Two #5: 2 x 0.307 = 0.614 sq in., at least 0.432 - OK4Footing is 12" thick, more than 8": at least one bar at the top and one at the bottom OKRESULT: two continuous #5 bars, one top and one bottomAreas computed from printed diameters. Plain footings supporting walls in SDC C-F (CBC 1905.6.2).CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: What the CBC Prints for Plain Concrete Footings

2025 CBC Section 1905.6.2 says structures in Seismic Design Category C, D, E or F shall not have structural plain concrete elements except as listed. Item 3 permits plain concrete footings supporting walls provided they have not fewer than two continuous longitudinal reinforcing bars. The bars may not be smaller than No. 4 and must have a total area of not less than 0.002 times the gross cross-sectional area of the footing. For footings thicker than 8 inches, not fewer than one bar must be provided at the top and bottom of the footing, and continuity of reinforcement must be provided at corners and intersections.

Step 2: Get the Bar Area From the Printed Diameter

The Caltrans Section 52-1.04 table gives each bar's nominal diameter, and the cross-sectional area of a round bar is 0.7854 x diameter squared. #4 (0.500 in.) = 0.196 sq in.; #5 (0.625 in.) = 0.307; #6 (0.750 in.) = 0.442; #8 (1.000 in.) = 0.785. Multiply by the number of bars to get the total steel area and compare it with the required area.

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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