According to code, what is the maximum diameter of a hole that may be bored in a 2 by 10 joist?

According to code, what is the maximum diameter of a hole that may be bored in a 2 by 10 joist?

• A. 2-1/2
• B. 1
• C. 2
• D. 3

Answer: (D)

Holes bored in a joist are limited in size to preserve bending strength. The standard rule is that the hole diameter should not exceed about one-third of the joist depth. A 2 by 10 joist has an actual depth of 9.25 inches; one-third of that is roughly 3.08 inches. So the largest hole that can be bored without reducing strength beyond the allowed limit is 3 inches. The other given sizes are smaller, but they’re not the maximum you’re allowed; 3 inches is the correct maximum.

Holes bored in a joist are limited in size to preserve bending strength. The standard rule is that the hole diameter should not exceed about one-third of the joist depth. A 2 by 10 joist has an actual depth of 9.25 inches; one-third of that is roughly 3.08 inches. So the largest hole that can be bored without reducing strength beyond the allowed limit is 3 inches. The other given sizes are smaller, but they’re not the maximum you’re allowed; 3 inches is the correct maximum.