Yes, a slab needs to be grounded for a residential addition.Code Reference

[National Electrical Code (NEC) 250.53](https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=70&edition=2020)

Exception

The exception to this requirement is if the slab is isolated from the earth and from all other conductive objects by at least 2 feet of nonconductive material.

Grounding Method

The slab can be grounded by using one of the following methods:

Grounding Electrodes

Copper rods, pipes, or plates driven into the earth

Concrete-Encased Electrode

A steel reinforcing bar or mesh embedded in the concrete slab

Other Approved Methods

As permitted by the NEC and local regulations

Justification:

Grounding the slab helps to protect people and equipment from electrical shock and fire hazards. It provides a low-resistance path for electrical current to flow back to the grounding system and the earth. This prevents dangerous voltages from accumulating on the slab and its associated equipment and structures. Flag for review