How do I ground a detached garage electrical panel properly in New Brunswick soil?

A detached garage in New Brunswick requires its own grounding electrode system at the garage, separate from the house — and NB's soil conditions, frost depth, and moisture levels all affect how you do it correctly.

This is not a DIY project. All electrical work in NB garages requires a permit and a licensed electrician. That said, understanding the requirements helps you have an informed conversation with your electrician and verify the work is done properly.

The Two-Structure Grounding Rule

When a detached garage receives power from the house via a feeder cable, the NB Electrical Code (which adopts the Canadian Electrical Code, Part I) treats the garage as a separate structure with its own grounding requirements. The garage sub-panel needs two independent grounding electrodes at the garage itself — you cannot simply rely on the grounding back at the house panel through the feeder. At the garage sub-panel, the neutral and ground buses must also be bonded together (unlike in the house panel, where they are kept separate after the main disconnect). Your electrician will know this distinction, but it's worth confirming.

Grounding Electrode Options in NB

The most common grounding electrode for a detached garage in New Brunswick is a ground rod — a copper-clad steel rod, minimum 5/8 inch diameter and 8 feet long, driven vertically into the soil beside the garage. NB's high soil moisture content (thanks to the Maritime climate and significant annual precipitation) generally provides good ground rod conductivity. However, the rod must be driven to its full depth, which means the top of the rod ends up below grade — typically 4-6 inches underground to protect it from frost heave and physical damage.

Because NB frost depth runs 4 to 5 feet, the top portion of a ground rod will be in freeze-thaw territory every winter. This is normal and acceptable — the rod is driven deep enough that the majority of its length is in stable, moist soil below the frost line where conductivity is consistent year-round. The connection between the ground rod and the grounding electrode conductor (GEC) must be made with a listed clamp rated for direct burial, not a standard pipe clamp. This connection point is the most common failure in amateur installations.

If a single ground rod tests above 25 ohms resistance, the CEC requires a second ground rod driven at least 6 feet away from the first. In practice, most NB electricians install two rods automatically on detached garage sub-panels rather than testing and potentially having to come back — it's inexpensive insurance and good practice.

The Grounding Electrode Conductor

The wire connecting the ground rod(s) to the garage sub-panel is the grounding electrode conductor (GEC). For most residential garage sub-panels (100-amp or 125-amp service), this is a #6 AWG bare or green-insulated copper wire. It must run in a continuous, unspliced length from the panel to the ground rod clamp. Where it passes through the garage wall or foundation, it needs protection — typically a short section of conduit or a bushing to prevent abrasion damage.

NB Soil Considerations

New Brunswick's soil varies considerably across the province. Sandy coastal soils around Shediac and the Northumberland Shore drain quickly and can have higher ground rod resistance in dry summer months — though this is rarely a problem given NB's rainfall. Clay-heavy soils common in the Saint John River valley and parts of Fredericton hold moisture well and typically provide excellent grounding conductivity. Rocky terrain in parts of northern NB and the Fundy coast can make driving a full 8-foot ground rod difficult — in these situations, your electrician may use a ground plate electrode (a buried copper plate) or a concrete-encased electrode (rebar in the garage footing, sometimes called a Ufer ground) as an alternative. The concrete-encased option is particularly effective and must be planned before the slab is poured — it cannot be added afterward.

Practical Tips

If your garage slab hasn't been poured yet, tell your electrician before the concrete work begins. A concrete-encased electrode (20 feet of bare #4 copper wire or rebar encased in the footing) is one of the most effective grounding methods available and costs almost nothing to add at the forming stage. Once the slab is poured, that opportunity is gone permanently.

Make sure your electrical permit covers both the feeder from the house and the garage sub-panel installation — some homeowners mistakenly pull a permit only for the house-side work. The garage grounding system will be inspected as part of the electrical rough-in and final inspection.

For related electrical contractors in your area, the New Brunswick Construction Network directory at newbrunswickconstructionnetwork.com lists licensed electricians working across NB. Need help finding a garage builder to coordinate the full project? New Brunswick Garages can match you with local contractors for free.