Flat-top underfloor raceways over 4 in. but not over 8 in. wide, with a minimum 1 in. spacing between raceways, shall be covered with concrete to a depth of not less than 1 in. Raceways spaced less than 1 in. apart shall be covered with concrete to a depth of _____.
a) 1 in.
b) 1½ in.
c) 2 in.
d) 4 in.
See answer and applicable Code reference
The correct answer is: b) 1½ in.
Article 390 outlines the requirements for underfloor raceways. As per 390.4(B), raceways sized as noted above and spaced less than 1 in. apart shall be covered with concrete to a depth of 1½ in.
