What is the minimum clear cover for bars that are in contact with soil?

• A. 1 inch
• B. 2 inches
• C. 3 inches
• D. 4 inches

Answer: (C)

When reinforcement is in contact with soil, the concrete surrounding it must act as a durable barrier against moisture, chlorides, sulfates, and other aggressive substances in the ground. That protection is achieved with a sufficient concrete cover over the bars. In typical soil conditions, the minimum clear cover is three inches. A smaller cover would leave the steel more exposed to corrosion and chemical attack, shortening its life and compromising durability. A larger cover, like four inches, provides extra protection but isn’t required as the minimum in standard soil conditions. So three inches is the appropriate minimum.