What is the maximum spacing for double floor joists that are separated to allow installation of piping?

What is the maximum spacing for double floor joists that are separated to allow installation of piping?

• A. 3 feet on center
• B. 4 feet on center
• C. 5 feet on center
• D. 6 feet on center

Answer: (B)

When you separate two floor joists to create a chase for piping, you still must keep the joists spaced close enough to carry the floor load effectively. Four feet on center is the maximum spacing that allows room for piping while preserving adequate stiffness and load transfer in the floor system. If the gap between the joists were larger, the floor would span more unbraced distance, increasing deflection under live loads and making it harder to support the piping properly without added structural work. Keeping the separation to four feet provides enough clearance for typical piping while maintaining the floor’s structural integrity. Smaller spacings would simply reduce the available space for piping but aren’t required here, since four feet already balances both needs.

When you separate two floor joists to create a chase for piping, you still must keep the joists spaced close enough to carry the floor load effectively. Four feet on center is the maximum spacing that allows room for piping while preserving adequate stiffness and load transfer in the floor system. If the gap between the joists were larger, the floor would span more unbraced distance, increasing deflection under live loads and making it harder to support the piping properly without added structural work. Keeping the separation to four feet provides enough clearance for typical piping while maintaining the floor’s structural integrity. Smaller spacings would simply reduce the available space for piping but aren’t required here, since four feet already balances both needs.