When framing a header opening in a load-bearing wall using California prescriptive methods, what is the maximum span allowed for a double 2x8 Douglas Fir-Larch header supporting a roof and ceiling load only?
Correct Answer
A) 8 feet
According to California Residential Code Table R602.7(1), a double 2x8 Douglas Fir-Larch header can span up to 8 feet when supporting roof and ceiling loads only. This table provides prescriptive header spans based on species, size, and loading conditions.
Why This Is the Correct Answer
California Residential Code Table R602.7(1) provides prescriptive header spans for load-bearing walls. For a double 2x8 Douglas Fir-Larch header supporting roof and ceiling loads only (no floor load above), the maximum prescriptive span is 8 feet. This span accounts for the combined bending strength of two 2x8 members with the structural properties of Douglas Fir-Larch, one of the stronger common framing species. The 'roof and ceiling only' condition is less demanding than carrying a floor load above, which would reduce the allowable span.
Why the Other Options Are Wrong
Option B: 12 feet
12 feet exceeds what a double 2x8 DF-L header can prescriptively span for any loading condition in Table R602.7(1). To achieve a 12-foot span, a larger header (such as a double 2x12 or an engineered LVL) would be required. Selecting 12 feet reflects an overestimate of the double 2x8's load-carrying capacity.
Option C: 10 feet
10 feet also exceeds the prescriptive limit for a double 2x8 DF-L under roof and ceiling loads. While 10 feet is closer to the actual answer than 12 feet, it still surpasses what the code table allows. For spans in the 9–10 foot range, a double 2x10 would be the prescriptive minimum under roof/ceiling loads.
Option D: 6 feet
6 feet understates the capacity of a double 2x8 DF-L header. This size header can span up to 8 feet under roof/ceiling loads, so limiting it to 6 feet would result in unnecessary over-engineering or rejection of a compliant design. This answer may appeal to overly conservative candidates.
Memory Technique
Double 2x8 = 8-foot max span (roof/ceiling only). The number 8 appears in both the lumber size (2x8) and the maximum span (8 feet). When you see '2x8,' think '8 feet.' If there's a floor load above, the span drops — size up to 2x10 or 2x12.
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