When installing engineered lumber I-joists in California, what is the minimum bearing length required at intermediate supports according to manufacturer specifications typically referenced in the CRC?
Correct Answer
A) 1-3/4 inches
CRC Section R502.8 requires engineered lumber products to be installed per manufacturer specifications. Most I-joist manufacturers specify a minimum 1-3/4 inch bearing length at intermediate supports to ensure proper load transfer and prevent web crippling. End bearings typically require 1-3/4 inches minimum as well.
Why This Is the Correct Answer
CRC Section R502.8 requires engineered lumber products to be installed per manufacturer specifications. Industry-standard I-joist manufacturers (APA, TJI, etc.) uniformly specify a minimum 1-3/4 inch bearing length at intermediate supports. This ensures adequate load transfer from the web and flanges to the bearing surface and prevents web crippling under concentrated loads.
Why the Other Options Are Wrong
Option B: 2-1/2 inches
2-1/2 inches is not the standard manufacturer-specified minimum for intermediate bearing. It exceeds the required minimum and is not cited in typical I-joist installation guides or CRC-referenced specifications.
Option C: 3-1/2 inches
3-1/2 inches corresponds to a standard 2x4 stud width and might seem logical, but it is not the minimum bearing requirement for I-joists at intermediate supports. It is overly conservative relative to published manufacturer guidelines.
Option D: 1-1/4 inches
1-1/4 inches is less than the minimum required by I-joist manufacturers. Insufficient bearing can cause web crippling and localized failure at the support point, which is why 1-3/4 inches is the established minimum.
Memory Technique
1-3/4 inches is the same as a standard 2x lumber actual thickness (1-1/2 inches) plus a 1/4-inch margin — or think of it as 'one and three-quarters, like a good sandwich.' This dimension appears across many engineered lumber specs, so it's worth anchoring as a reference number.
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