Soil Bearing Values from the Presumptive Load-Bearing Table
"Soil Bearing Values from the Presumptive Load-Bearing Table" is lesson 1 of 6 in the Manufactured Housing (C-47) Learning Hub. It opens with "Why You Check the Soil Before You Size Anything" and works through 5 short steps, then a worked example you can check yourself against.
One-time purchase, no subscription. Law & Business included.
Steps in this lesson
Why You Check the Soil Before You Size Anything
Read Table R401.4.1(1)
Match the Soil to a Row by Its Symbol
When the Table Does Not Apply
California Soils Reports and the Permit
The worked example in the course applies this lesson to a realistic job in 4 steps, from "Pick one design pressure for the pad" through "See what the weaker soil costs you".
What you'll be able to do
Explain the main idea of "Soil Bearing Values from the Presumptive Load-Bearing Table" in plain language you can use on the exam.
Apply this step with confidence: "Match the Soil to a Row by Its Symbol".
Apply this step with confidence: "When the Table Does Not Apply".
Apply this step with confidence: "California Soils Reports and the Permit".
Test yourself on the worked example and the quick-check quiz inside the classroom.
The diagram for this lesson, exactly as it appears in the Learning Hub.
The first steps of this lesson
Step 1: Why You Check the Soil Before You Size Anything
Every pier footing on a manufactured home setup is sized from what the soil can carry. 2025 CRC R401.2 requires foundation construction to transmit all loads to the supporting soil, and R401.4.1 says that in lieu of a complete geotechnical evaluation the load-bearing values in Table R401.4.1(1) and the soil classes in Table R401.4.1(2) are assumed. The CSLB C-47 Study Guide lists "Lot evaluation" under Planning and Estimating and "Support and foundation systems" under Installation, so this is exam territory.
Step 2: Read Table R401.4.1(1)
The 2025 CRC prints these presumptive pressures: crystalline bedrock 12,000 psf; sedimentary and foliated rock 4,000 psf; sandy gravel and/or gravel (GW and GP) 3,000 psf; sand, silty sand, clayey sand, silty gravel and clayey gravel (SW, SP, SM, SC, GM and GC) 2,000 psf; and clay, sandy clay, silty clay, clayey silt, silt and sandy silt (CL, ML, MH and CH) 1,500 psf. 2025 CBC Table 1806.2 prints the same vertical foundation pressures, and CBC 1806.2 says design values may not exceed them unless data to substantiate higher values are submitted and approved.
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.
Independent exam preparation. Contractors Classroom is not affiliated with the Contractors State License Board, and no course can guarantee a passing result.
