How to Properly Install Exterior Electrical Conduit

Conduit is the backbone of any exterior electrical run, providing a physical shield against the elements, pests, and accidental damage. When you choose to run power along the outside of your home, you are inviting weather to test the integrity of your seals. Done well, this installation will last for decades, keeping your wiring bone-dry and your home's exterior clean and organized. Great work starts with planning your path. Avoid unnecessary bends that make pulling wire impossible later, and ensure that every point where the conduit enters the house is sealed with exterior-grade duct seal or silicone. When you secure your pipe firmly to the siding, you prevent the vibration and sagging that eventually cause connections to loosen and fail.

  1. Map the straightest path. Use a chalk line or pencil to map the straightest path from your power source to the outlet box. Keep the conduit away from low-traffic areas where it could be bumped or caught by gardening equipment.
  2. Mount boxes for water shedding. Attach your exterior-rated FS or FD boxes to the wall using anchors appropriate for your siding material. Use a rubber gasket behind the box if your siding is uneven to ensure a tight, weather-resistant fit.
  3. Cut and ream conduit cleanly. Measure the distance between your boxes and cut your conduit lengths using a hacksaw or a conduit cutter. If using metallic conduit, use a reamer to smooth the inside of the cut edges so you do not strip your wire insulation during the pull.
  4. Strap for strength and longevity. Place a one-hole or two-hole strap within 36 inches of each junction box and every 5 to 10 feet along the run. Use stainless steel or hot-dipped galvanized hardware to prevent rust streaks from staining your siding.
  5. Connect with rain-tight joints. Connect your lengths of conduit using rain-tight couplings and connectors. Tighten all set screws firmly, but avoid over-torquing them to the point of stripping the threads.
  6. Seal against weather and pests. Pack the area around the conduit where it enters the building with exterior-grade duct seal or silicone sealant. This stops cold air, water, and insects from entering your wall cavity.