Underground wiring to a detached garage or shed

A detached garage or shed feeder combines route planning, load planning, trench work, cable or raceway selection, and inspection timing.

Use this guide before trenching or buying cable for a detached garage, shed, pump, gate, workshop, or outdoor structure fed from a dwelling or service.

When to use this guide

• A homeowner wants lights and receptacles in a detached garage or shed.
• A workshop or future EV charger could make a small underground run become a feeder, subpanel, or service-capacity question.
• A trench route is being planned and inspection-before-backfill timing must be settled.

Inputs to gather

• Structure type, distance, route sketch, source panel, destination equipment, and whether the building is attached or detached.
• Current and future loads: lights, receptacles, heater, compressor, welder, EV-ready conduit, door opener, pump, or subpanel.
• Utility locate ticket, property constraints, frost/settlement concerns, driveway or walkway crossings, and landscaping constraints.
• Wiring method under review: direct-burial cable, PVC conduit, rigid metal conduit, or other authority-approved method.
• Inspection timing, open-trench photos, backfill plan, warning/marker tape, and transition details above grade.

Project path matrix

Working checklist

• Confirm the project branch: A homeowner wants lights and receptacles in a detached garage or shed.
• Measure or photograph the first hard inputs: Structure type, distance, route sketch, source panel, destination equipment, and whether the building is attached or detached. Current and future loads: lights, receptacles, heater, compressor, welder, EV-ready conduit, door opener, pump, or subpanel.
• Record the decision basis: A short shed circuit and a detached workshop feeder are different planning jobs. Locate processes, inspection timing, cover, marking, backfill, and detached-structure requirements vary by authority.
• Keep the handoff package together: Locate confirmation, route sketch, trench photos, open-trench inspection notes, and backfill photos.
• Stop before work proceeds if this applies: The run crosses driveways, public utility areas, shared property, pools/hot tubs, or unknown underground services.

Workflow

1. Call or request locates before any excavation planning becomes field work.
2. Build the load list first so the trench is not sized around only today’s light and receptacle needs.
3. Sketch the route, depth-control points, above-grade transitions, and future access needs.
4. Choose wiring method only after environment, mechanical protection, pulling, and inspection timing are reviewed.
5. Keep the trench open until the required local inspection or review step is complete.

Decision checkpoints

• A short shed circuit and a detached workshop feeder are different planning jobs.
• Future EV, heater, welder, compressor, or subpanel needs can change service-capacity and voltage-drop discussions.
• Direct burial, conduit, and above-grade transitions have different product, protection, and inspection questions.
• Backfill, settlement, and driveway crossings can affect long-term reliability even when the electrical calculation looks simple.

Canada-specific checks

• Locate processes, inspection timing, cover, marking, backfill, and detached-structure requirements vary by authority.
• Underground work may need inspection before concealment or backfill.
• Confirm current Canadian Electrical Code context, local authority requirements, product markings, utility rules, and qualified review before work begins.

Project package to keep

• Locate confirmation, route sketch, trench photos, open-trench inspection notes, and backfill photos.
• Load-list worksheet and future-load notes.
• Cable or conduit markings, product data, and above-grade transition details.
• Voltage-drop and conduit-fill outputs where relevant.

Stop and get local review

• The run crosses driveways, public utility areas, shared property, pools/hot tubs, or unknown underground services.
• The detached structure may need a subpanel, disconnect, grounding/bonding review, or future EV/heater loads.
• The trench will be backfilled before inspection timing is confirmed.

Questions to settle before work starts

• Which local authority, utility, property authority, product listing, or manufacturer instruction controls this wire and raceway decision?
• Which inputs are measured from the field or nameplate, and which are still assumptions from a quote, drawing, or memory?
• Which part of the work will be concealed, energized, interconnected, or purchased before review if the sequence is not controlled?
• Which single assumption would change the equipment choice, installation path, cost, schedule, or inspection timing?
• Who will keep the final photos, calculator outputs, product documents, permit or utility records, and commissioning notes?

Use the related tools

• Use the Load List kVA and Amps Calculator to separate current and future garage loads.
• Use the Voltage Drop Calculator for long detached-building runs.
• Use the Conduit Fill Calculator if a raceway method is selected.

Public reference starting points

• ESA buried wiring information sheet - Ontario underground wiring workflow example.
• Technical Safety BC underground installations bulletin - British Columbia underground installation authority example.
• EleCanada utility locate colour chart - Use as a visual handoff for locate-colour terminology; local locate instructions still govern.

Local standards and authority note

Confirm underground cover, wiring method, bonding, grounding, inspection, and utility locate requirements locally before trench work.