Check concrete rebar cover against ACI 318 minimum requirements. Enter slab thickness, top and bottom clear cover, and rebar size to calculate net effective depth and see pass/fail against ACI 318 cover minimums by exposure condition. Includes full ACI 318 cover table for all standard exposure conditions.
Concrete cover is the clear distance from the concrete surface to the face of the reinforcing bar. ACI 318-19 Section 20.6.1 specifies minimum cover based on exposure conditions: 3/4 inch for interior slabs not exposed to weather (for #5 bars and smaller), 1.5 to 2 inches for concrete exposed to weather, and 3 inches for concrete cast against and permanently in contact with the ground.
Effective depth (d) is the key parameter for structural design — it is measured from the compression face of the member to the centroid of the tension reinforcement. For a slab with bottom bars: d = h − bottom cover − db/2, where h is total thickness and db is bar diameter. Increasing effective depth significantly improves moment capacity.
Concrete cover is the clear distance from the concrete surface to the nearest rebar face. It protects steel from corrosion, fire, and damage. ACI 318 sets minimums by exposure condition.
Interior slabs not exposed to weather: 3/4 in (small bars). Exposed to weather #5 and smaller: 1.5 in; #6+: 2 in. Cast against earth: 3 in. Always check your specific exposure class and project specifications.
Effective depth d = total thickness − bottom cover − half bar diameter. It is the distance from the compression face to the tension steel centroid. Used in flexural and shear strength calculations.
Insufficient cover accelerates rebar corrosion, leading to concrete spalling and structural deterioration. In coastal or marine environments the risk is even higher. Minimum cover is a code floor — engineers often specify more.
Net effective depth and ACI 318 concrete cover compliance check by exposure condition.
Concrete cover meters and rebar locators for quality control and inspection.
Shop Express Tools →Concrete cover is the clear distance from the concrete surface to the nearest rebar face. It protects steel from corrosion, fire, and damage. ACI 318 sets minimums by exposure condition.
Interior slabs not exposed to weather: 3/4 in (small bars). Exposed to weather #5 and smaller: 1.5 in; #6+: 2 in. Cast against earth: 3 in. Always check your specific exposure class and project specifications.
Effective depth d = total thickness − bottom cover − half bar diameter. It is the distance from the compression face to the tension steel centroid. Used in flexural and shear strength calculations.
Insufficient cover accelerates rebar corrosion, leading to concrete spalling and structural deterioration. In coastal or marine environments the risk is even higher. Minimum cover is a code floor — engineers often specify more.
Clear cover to top face of bar
Clear cover to bottom face of bar
| Exposure Condition | Top (in) | Bottom (in) |
|---|---|---|
| Cast in place — not exposed to weather, not in contact with ground (slabs, walls, joists) | 0.75 | 0.75 |
| Cast in place — not exposed to weather, beams/columns | 1.5 | 1.5 |
| Exposed to weather — #6–#18 bars | 2 | 2 |
| Exposed to weather — #5 and smaller | 1.5 | 1.5 |
| In contact with ground / cast against earth | 3 | 3 |
| Corrosive environment / Class F2/F3 freeze-thaw | 2 | 2 |
Source: ACI 318-19 §20.6.1. Always consult the project structural engineer of record for project-specific requirements.