Which of the following size, type, grade, and spacing of floor joists (excluding built up wood beams) are indicated for some part of the first floor? a) 2x6, Select Structural, 16 inches on center
b) 2x8, No.1 Grade, 24 inches on center
c) 2x10, Construction Grade, 12 inches on center
d) 2x12, Standard Grade, 18 inches on center