Manufactured Housing (C-47) · Lesson 2 of 6

Sizing Pier Footings from Pier Load and Soil Pressure

"Sizing Pier Footings from Pier Load and Soil Pressure" is lesson 2 of 6 in the Manufactured Housing (C-47) Learning Hub. It opens with "Every Pier Needs a Footing That Fits the Soil" and works through 5 short steps, then a worked example you can check yourself against.

Open the free trialSee pricing

One-time purchase, no subscription. Law & Business included.

Steps in this lesson

  1. Every Pier Needs a Footing That Fits the Soil
  2. Find the Area: Load Divided by Pressure
  3. Check the Footing Minimums
  4. Depth, Level and Slope
  5. What Still Comes From the Permit

The worked example in the course applies this lesson to a realistic job in 5 steps, from "Required area" through "Compare with better soil".

What you'll be able to do

  • Explain the main idea of "Sizing Pier Footings from Pier Load and Soil Pressure" in plain language you can use on the exam.
  • Apply this step with confidence: "Check the Footing Minimums".
  • Apply this step with confidence: "Depth, Level and Slope".
  • Apply this step with confidence: "What Still Comes From the Permit".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Pier Footing: Load, Soil Pressure, ThicknessPLAN VIEW - 22 x 22 in PAD, 8 x 16 in PIERPIER8 x 16 inP = 7 in(22 - 8) / 2P = 3 in22 inPIER LOAD 4,800 lb ON CL CLAY, 1,500 psf1 Area = load / pressure 4,800 / 1,500 = 3.2 sq ft2 3.2 x 144 = 460.8 sq in3 Side = sqrt(460.8) = 21.5, use 22 in4 22 x 22 = 484 sq in = 3.36 sq ft 3.36 x 1,500 = 5,042 lb ≥ 4,800 OK5 Projection (22 - 8) / 2 = 7 in P ≤ T, so T = 7 in (min 6 in)Use 22 x 22 x 7 in pad on 1,500 psf clay (CL)On 2,000 psf silty sand (SM): 19 x 19 x 6 in pad (projection 5.5 in)Pad minimums: 12 in wide, 6 in thick, projection 2 in to TSource: 2025 CRC R403.1.1 and Table R401.4.1(1). The 4,800 lb pier load is given for the example.CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: Every Pier Needs a Footing That Fits the Soil

A pier puts a heavy load on a few square inches of block, and the footing spreads it over enough soil that it does not settle. 2025 CRC R403.1.1 says the size of footings supporting piers and columns shall be based on the tributary load and the allowable soil pressure in accordance with Table R401.4.1(1). R403.1 requires footings to be supported on undisturbed natural soils or engineered fill, and R401.2 requires fill that supports footings to be designed, installed and tested to accepted engineering practice.

Step 2: Find the Area: Load Divided by Pressure

Required bearing area in square feet equals the pier load in pounds divided by the allowable soil pressure in psf from Table R401.4.1(1). The CRC tells you to use the tributary load; the load number itself comes from the permitted foundation plan or the engineer, so this lesson gives it to you. Convert to square inches (multiply by 144), take the square root for a square pad, and round up to the next whole inch.

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.

More lessons for this trade

Browse all lesson previews

Ready to practice for real?

Try the real classroom free, no sign-up, or get the full course for your trade.

Open the free trialSee pricing

Independent exam preparation. Contractors Classroom is not affiliated with the Contractors State License Board, and no course can guarantee a passing result.