What is the minimum bearing length required for floor joists bearing on wood sill plates according to the California Residential Code?
Correct Answer
C) 1.5 inches
CRC Section R502.6 requires floor joists to have a minimum bearing length of 1.5 inches when bearing on wood sill plates or girders. This minimum bearing ensures adequate load transfer and prevents crushing of the wood fibers under concentrated loads from the floor system.
Why This Is the Correct Answer
CRC Section R502.6 specifies a minimum bearing length of 1.5 inches for floor joists resting on wood sill plates or wood girders. This minimum ensures adequate contact area for load transfer from the floor system into the foundation structure, preventing crushing or rolling of the joist end under load.
Why the Other Options Are Wrong
Option A: 2 inches
2 inches exceeds the code minimum of 1.5 inches. While 2 inches of bearing is acceptable (and often preferred in practice), it is not the minimum required by CRC R502.6. Selecting 2 inches confuses the minimum with a common practical standard.
Option B: 3 inches
3 inches significantly exceeds the 1.5-inch minimum. A 3-inch bearing length would be appropriate for masonry or concrete supports (which have a separate 3-inch minimum under CRC R502.6), not for wood-to-wood bearing on sill plates.
Option D: 1 inch
1 inch is below the code minimum and would not provide adequate bearing area for safe load transfer. CRC requires at least 1.5 inches — 1 inch is an insufficient and non-compliant bearing length for floor joists on wood sill plates.
Memory Technique
Remember '1.5 inches = one full piece of lumber nominal thickness.' A 2x4 or 2x6 has an actual thickness of 1.5 inches — so the minimum bearing on wood is essentially 'the width of one stud face.' This real-world connection makes the number easy to recall.
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