Section Table 20.6.1.3.1/Specified Concrete Cover
ACI 318-19 Table 20.6.1.3.1 specifies minimum concrete cover for reinforcement based on exposure condition and member type.
The minimum concrete cover over reinforcing bars varies by exposure condition and member type. Concrete cast against and permanently in contact with earth requires 3 inches of cover. Concrete exposed to weather with larger bars (No. 6 through No. 18) requires 2 inches. Concrete exposed to weather with No. 5 bars and smaller requires 1.5 inches. Interior concrete not exposed to weather requires 0.75 to 1.5 inches depending on member type and bar size.
Why this section exists
Concrete cover protects reinforcing steel from corrosion. When the cover is too thin, moisture and chlorides penetrate the concrete and reach the reinforcement, causing it to corrode. Corroding steel expands, cracking and spalling the concrete, which accelerates the deterioration cycle. Adequate cover is the primary defense against reinforcement corrosion and is essential for the long-term durability of concrete structures.
What plan reviewers look for
Plan reviewers check the structural general notes and section details for concrete cover dimensions. They verify that the cover matches the exposure condition (cast against earth, exposed to weather, or protected). They pay particular attention to foundation elements (which require 3-inch cover), exterior walls, and parking structures (which are exposed to weather and de-icing chemicals).
Common violations
Related ACI 318 requirements
Section 25.4.2 uses the concrete cover to calculate development lengths.Section 20.6.1.4 provides cover requirements for prestressed concrete. Section 26.4.1 covers construction tolerances for reinforcement placement, which affect whether the specified cover is achieved in the field.