The maximum size of conduit or pipe shall NOT exceed _______ of the thickness of the concrete.

• A. 1/3
• B. 1/2
• C. 1/4
• D. 1/5

Answer: (A)

Openings for conduits in concrete must leave enough material around them to keep the member strong. The rule sets a limit so the conduit diameter does not exceed one-third of the concrete thickness. This preserves adequate concrete cover and cross‑section, helping the slab or wall carry loads, resist cracking, and maintain durability. For example, in a 6-inch-thick slab, the largest conduit allowed would be about 2 inches in diameter. Larger openings would weaken the member too much; smaller ones are more restrictive than required. So one-third of the thickness is the correct limit.