What is nominal cover in concrete?

Answer 1

Cover is the distance from the surface of the concrete to the surface of the reinforcement bar.

Nominal cover (Cnom) is the cover that the designer, and steel fixer tries to achieve.

Minimum cover (Cmin) is the absolute minimum cover that must be maintained for durability reasons after taking into account deviations in as built cover. Acceptable values of Cmin are given by BS8500 and EN 206. (Warning prior to BS8500, and EN206 minimum cover was also used as a term to describe nominal cover to the outer layer of bars).

Δc is the cover tolerance. (Cnom must be >= Cmin + Δc)

Note: bar bending/cutting tolerance for bars fitting between two fixed faces (defined in BS8666) is allowed for separately by reducing the scheduled dimensions of bars fitting between two fixed faces by +5mm (bending) +25mm (cutting) in the bar schedules.