Final answer:
The correct spacing for attaching metal furring channels to bar joists with a furred ceiling is 24" on center maximum, and they should run at right angles to the bar joists.
Step-by-step explanation:
The metal furring channels should be attached to bar joists with a furred ceiling 24" on center maximum, at right angles to the bar joists. When installing metal furring channels or hat channels for a suspended ceiling or wall framing, adherence to proper spacing is critical for structural stability. Channels should be securely fastened to the bar joists to ensure they effectively support the weight of the ceiling material.