A single row of solid blocking is installed between 17 floor joists. Each block is cut 14-1/2 in. long. What total block length is required?
Correct Answer
A) 19.3 ft
Seventeen joists create 16 spaces between joists. Total block length is 16 x 14.5 = 232 in.; 232/12 = 19.3 ft. Other choices count the wrong number of spaces or use a different block length.
Why This Is the Correct Answer
Seventeen joists create 16 spaces between joists. Total block length is 16 x 14.5 = 232 in.; 232/12 = 19.3 ft. Other choices count the wrong number of spaces or use a different block length.
Why the Other Options Are Wrong
Option B: 17.1 ft
blocking length, choice a: 17.1 ft backs into 1.01 when divided by 17; the accepted setup gives 1.14 on that same base.
Option C: 18.1 ft
blocking length, choice b: 18.1 ft backs into 1.29 when divided by 14; the accepted setup gives 1.38 on that same base.
Option D: 20.5 ft
blocking length, choice c: 20.5 ft backs into 41 when divided by 1/2; the accepted setup gives 38.6 on that same base.
Memory Technique
Say the blocking length rule aloud as a chain; the chain ends at 19.3 ft, not an intermediate stop.
Reference Hint
Open Carpentry and Building Construction, 2016; use the index entry or section for "Solid blocking takeoff between floor joists" to confirm that Seventeen joists create 16 spaces between joists.
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