Underground Power to a Detached Garage, Shed or Outbuilding

Direct burial depths, at a glance (CEC / OESC Rule 12-012 & Table 53)

Every one of these needs an ESA permit before you dig. Under the Canadian Electrical Code (CEC Part I) and Ontario Electrical Safety Code (OESC), direct burial requires NMWU (Non-Metallic Wet Underground) or TECK90 cable. Note: US UF-B cable is not CEC approved in Canada.

The same depths, in plain numbers (minimum cover from finished grade to the top of the cable or conduit):

• Outdoor receptacle or yard lighting: 600 mm (24 in) with NMWU or TECK90 direct burial.
• Shed or gazebo branch circuit: 600 mm (24 in) with NMWU or TECK90 direct burial.
• Garage feeder / subpanel supply: 600 mm (24 in) with NMWU or TECK90 direct burial, or 450 mm (18 in) in rigid PVC conduit.
• Under a driveway or other vehicle area: 900 mm (36 in) with direct burial cable, or 600 mm (24 in) in rigid PVC conduit.
• Pool, hot tub or spa equipment: varies by installation — licensed electrical contractor only.

Add a minimum 75 mm (3 in) of clean sand above and below direct-buried cable and lay yellow warning tape partway up the trench. Solid rock and runs under a concrete slab have their own, shallower rules — the direct burial calculator covers them.

1. Single Branch Circuit vs. Subpanel Feeder

Before buying wire or digging a trench, decide how much electrical power your detached garage or shed will require:

• Single 120V Branch Circuit (15A or 20A): Ideal for simple shed lighting and 1 or 2 outlets for light power tools. Requires 14/2 NMWU (15A) or 12/2 NMWU (20A). No subpanel required, but a local disconnect switch (like a single-pole wall switch) at the shed door is required by CEC.
• Subpanel Feeder (30A to 100A, 120/240V): Required if you plan to run an air compressor, EV charger, 240V heater, or multiple power tools simultaneously. Requires a 4-conductor feeder (e.g. 8/3, 6/3, or 2/2/2/4 NMWU/TECK90) back to a dedicated double-pole breaker in the main home panel.

2. Main Disconnect Means at the Detached Building

CEC Section 6 and 26 require a single main disconnect means at any outbuilding fed by a subpanel or feeder. This allows anyone inside the garage or shed to shut off all power instantly in an emergency. This can be a main breaker inside the subpanel or an external weatherproof disconnect switch near the entry door.

3. Crucial 4-Wire Subpanel Rule: Separating Neutral & Ground

One of the most common ESA inspection failures for DIY garage wiring is improperly bonding the neutral bar inside a subpanel. Under Canadian Electrical Code:

• 4 Conductors Required: Hot 1 (Red), Hot 2 (Black), Neutral (White), and Ground (Bare/Green).
• Remove the Bonding Screw: The green neutral bonding strap/screw included with new panels MUST BE REMOVED in a subpanel. Neutral and ground buses must remain floating and isolated.
• Grounding Plate / Ground Rods: Detached structures fed by a subpanel must have their own ground electrode system (typically 2 ground plates or ground rods spaced at least 2 metres apart per CEC Rule 10-102) connected to the subpanel ground bus.

4. Protecting Wire From Frost Heave (Expansion Sleeves)

In Canadian climates (Ontario / GTA), freezing ground expands and moves vertically (frost heave). Rigid PVC conduit coming out of the ground into a building or main house wall must be fitted with an approved PVC Expansion Joint / Sleeve (CEC Rule 12-012). Without an expansion joint, winter ground movement will crack the conduit or rip the panel box right off the wall.

5. Interior Wiring Rules Inside Garages & Sheds

• Physical Protection: Romex / NMD90 wire running on unfinished garage walls below 1.5m (5 ft) off the floor must be protected from mechanical damage inside EMT conduit or PVC.
• GFCI Protection: Outlets in unfinished garages, sheds, or outdoors must have GFCI protection (CEC Rule 26-704).
• Weatherproof Covers: Outdoor receptacles must be equipped with "Extra-Duty" while-in-use wet location covers.

6. ESA Inspection Process in Ontario

When installing power to a detached garage or shed, the Electrical Safety Authority (ESA) requires a 2-stage inspection process:

1. Rough-In & Trench Inspection: Must occur while the trench is wide open (bedding sand + cable + warning tape visible) and before any drywall/insulation covers subpanel wiring.
2. Final Inspection: Conducted after all fixtures, receptacles, panel breakers, covers, and disconnect switches are fully trimmed out.

7. Acreage and multiple outbuildings

If you have a barn, workshop, pump house and a garage spread across a property, the same rules apply to each building, but long runs and shared loads need more planning up front:

• Longer runs mean more voltage drop. A feeder that is fine at 15 m can struggle at 100 m, especially with motors, compressors or welders. You may need a larger conductor than ampacity alone suggests. Check it with the Voltage Drop Calculator and size the conductor with the Wire Size Calculator.
• Add up the loads for the whole property. List what will run in each building, then check that the house panel and service have room for all of them together. The Load Calculator and Service Size Calculator are good places to start.
• Plan the layout before you dig. Decide whether buildings will be fed by separate feeders or one feeder that continues to the next building. Each building still needs its own disconnect and grounding; ask the ESA or a licensed contractor which arrangement they will accept.
• Install for the future. If more buildings or an EV charger might come later, installing larger conduit with a pull string now is far cheaper than re-trenching.
• Mind other things in the ground. Wells, septic systems, water lines and gas lines all matter on acreage. Call Ontario One Call (1-800-400-2255) for utility locates and keep a sketch of where your own cables and conduit run.
• Check the cover depths again for each crossing. A laneway or farm-equipment crossing is a vehicle area: use the 900 mm (36 in) direct-burial depth or 600 mm (24 in) in rigid PVC.

Outside Ontario?

The Canadian Electrical Code (CEC) is a national standard, but each province and territory adopts it with its own amendments, and the local authority enforces the version it has adopted. Burial depths, permit steps and inspection rules can differ from what is described here, so confirm the rules with your provincial regulator or local authority before you dig.

Why pool equipment is different

Pool and hot tub wiring sits in its own category — bonding requirements around water are stricter (CEC Section 68), and the depth and method depend heavily on the specific run and equipment. This is one of the few jobs on this list we'd say don't DIY any part of, not even the trench.