Manufactured Housing (C-47) · Lesson 3 of 6

Masonry Pier Height Limits and Wood-to-Ground Clearances

"Masonry Pier Height Limits and Wood-to-Ground Clearances" is lesson 3 of 6 in the Manufactured Housing (C-47) Learning Hub. It opens with "What the California Residential Code Prints About Piers" 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 California Residential Code Prints About Piers
  2. The Height Rule: Thickness Sets the Limit
  3. Piers Under Girders
  4. Keep Wood Away From the Ground
  5. Where These Rules Stop

The worked example in the course applies this lesson to a realistic job in 5 steps, from "Pier height" through "Check wood clearance".

What you'll be able to do

  • Explain the main idea of "Masonry Pier Height Limits and Wood-to-Ground Clearances" in plain language you can use on the exam.
  • Apply this step with confidence: "Piers Under Girders".
  • Apply this step with confidence: "Keep Wood Away From the Ground".
  • Apply this step with confidence: "Where These Rules Stop".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Masonry Pier Limits and Ground ClearancePIER UNDER A WOOD GIRDER (ELEVATION)GRADEWOOD GIRDERPIERfooting38 in42 inpier heightfooting top4 in below grade38 in = grade to girder bottom42 in = footing top to girder bottomR404.1.9 PIER HEIGHT = 38 + 4 = 42 inHollow 8 in pier: 4 x 8 = 32 inFAILCells solid: 10 x 8 = 80 inOKHollow 12 in pier: 4 x 12 = 48 inOKGirder pier: min 12 in, max 4 ftOKR304.1 girder 38 in vs 12 inOKR304.1 joists 38+ in vs 18 inOKHollow: length also max 3 x thicknessUse a 12 in nominal hollow masonry pier, 42 in tallCap with 4 in solid masonry or concrete, cap block, or filled top cellsIn SDC D0, D1, D2 piers need accepted engineering design (R404.1.9.4)Source: 2025 CRC R404.1.9, R404.1.9.1, R404.1.9.2, R404.1.9.4 and R304.1 item 1.CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: What the California Residential Code Prints About Piers

The HUD installation tables for manufactured home piers are not part of the California books used in this course. What the 2025 CRC does print is R404.1.9 Isolated Masonry Piers, which governs piers on foundations designed and permitted under the CRC. The permit plans say which design applies to a given home, so use this section and the plans together. Piers are built to R404.1.9 and the masonry rules of R606.

Step 2: The Height Rule: Thickness Sets the Limit

R404.1.9: hollow masonry piers have a minimum nominal thickness of 8 inches, a nominal height not exceeding four times the nominal thickness, and a nominal length not exceeding three times the nominal thickness. Where the hollow units are solidly filled with concrete or grout, the height may be up to ten times the nominal thickness. So an 8 in hollow pier tops out at 32 in, a 12 in hollow pier at 48 in, and an 8 in solid-filled pier at 80 in. R404.1.9.1 requires a cap: 4 inches of solid masonry or concrete, a masonry cap block, or the top-course cavities filled with concrete or grout.

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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