Holes bored in joists for piping or wiring should not exceed what fraction of the joist depth?

Holes bored in joists for piping or wiring should not exceed what fraction of the joist depth?

• A. One-third
• B. One-half
• C. One-quarter
• D. One-sixth

Answer: (A)

When you bore holes in joists, you’re removing material that carries bending loads. The joist’s strength in bending depends on its depth and the amount of wood left. To keep the joist from losing too much capacity, the widest hole you can safely drill for piping or wiring is one-third of the joist depth. Keeping the hole in the middle portion of the depth helps protect the critical fibers near the top and bottom surfaces, preserving both compression and tension strength. If a hole is larger than this or placed too close to the edges, the joist can weaken significantly and fail under load. So, one-third of the joist depth is the standard maximum for holes in this context, with smaller holes and proper placement being acceptable.

When you bore holes in joists, you’re removing material that carries bending loads. The joist’s strength in bending depends on its depth and the amount of wood left. To keep the joist from losing too much capacity, the widest hole you can safely drill for piping or wiring is one-third of the joist depth. Keeping the hole in the middle portion of the depth helps protect the critical fibers near the top and bottom surfaces, preserving both compression and tension strength. If a hole is larger than this or placed too close to the edges, the joist can weaken significantly and fail under load. So, one-third of the joist depth is the standard maximum for holes in this context, with smaller holes and proper placement being acceptable.