Conduit Wiring: A Practical Homeowner’s Guide

Most residential electrical runs in modern American homes use Romex (NM-B cable) tucked through wall cavities. But step into a basement, garage, workshop, or any exterior wall, and the wiring switches to conduit wiring — protective tubing that shields the conductors from physical damage and code-required exposure issues. Knowing the conduit options helps you make smart choices on garage subpanels, EV charger installs, and exterior lighting projects.

This guide breaks down the major conduit types, what code requires where, how to size conduit for your wires, and what a DIYer can reasonably tackle.

Why Conduit Is Used Instead of Romex

The National Electrical Code (NEC) requires conduit anywhere wiring is exposed to physical damage, sunlight, moisture, or specific occupancy types. Garages, unfinished basements, exterior walls, and any exposed run below 8 feet typically require conduit protection in residential applications.

Conduit also enables you to pull or replace wires later without opening walls. That makes it the smart choice for any installation that may need future upgrades — EV chargers, garage subpanels, workshop circuits, and outdoor power.

EMT (Electrical Metallic Tubing)

EMT is thin-wall steel conduit, the most common choice for indoor exposed runs in residential garages and basements. It is light, easy to bend with a hand bender, and connects with set-screw or compression fittings. Standard sizes are 1/2, 3/4, 1, 1-1/4, 1-1/2, and 2 inches.

EMT is not rated for direct burial outdoors. It can be used outdoors above ground if all fittings are weatherproof and the conduit is properly supported. Expect $1 to $4 per linear foot for the conduit, plus $0.50 to $5 per fitting.

Rigid Metal Conduit (RMC) and IMC

Rigid Metal Conduit is the heavyweight option — thick-wall galvanized steel that can be threaded and is rated for direct burial. Intermediate Metal Conduit (IMC) is a lighter version with similar protection. Both are used for service entrances, large feeders, and high-impact areas like exterior walls of commercial buildings.

For most residential projects, RMC is overkill. PVC is cheaper for direct-burial runs and EMT is cheaper for indoor exposed runs. RMC’s main residential use is service entrance from the meter to the main panel where physical impact is a concern.

PVC Conduit

PVC (specifically Schedule 40 and Schedule 80 gray electrical PVC) is the standard for direct-burial outdoor runs and damp locations. Schedule 40 works for most residential below-ground installations. Schedule 80 has thicker walls and is required where exposed to physical damage above ground.

PVC connects with solvent-welded fittings and is the easiest material to work with for most DIYers. Cost runs $0.40 to $2 per linear foot for Schedule 40, with fittings at $0.50 to $4 each. Burial depth is typically 18 inches for residential branch circuits — local code may differ.

Flexible Conduit (FMC and LFMC)

Flexible Metal Conduit (FMC, often called “Greenfield”) is a coiled metal tubing used for short runs to motors, water heaters, and HVAC equipment where vibration or movement would damage rigid conduit. Standard residential use is 6 to 36-inch whips connecting equipment to junction boxes.

Liquidtight Flexible Metal Conduit (LFMC) and Liquidtight Flexible Nonmetallic Conduit (LFNC) add a sealed plastic jacket for outdoor and damp-location use. These are common for exterior AC condenser whips, pool equipment, and hot tubs.

Sizing Conduit for the Wires Inside

NEC limits the percentage of conduit cross-section that wires can fill. The basic rule is 53% for one wire, 31% for two wires, and 40% for three or more wires. Tables in NEC Chapter 9 list exact wire counts for each conduit size and wire gauge.

For practical residential work: 1/2-inch conduit fits up to nine 12 AWG conductors or six 10 AWG. 3/4-inch fits up to sixteen 12 AWG. For a 50-amp EV charger circuit (three 6 AWG plus ground), use 1-inch conduit. Always size up rather than max out — easier pulls and room for future additions.

Bends and Pull Boxes

Code limits the total bends in any single conduit run between accessible points to 360 degrees. That equals four 90-degree bends. Beyond this, you have to install a pull box or junction box to relieve the pulling stress.

Each 90-degree bend adds significant pulling resistance. Even within code, planning long runs with sweeps (large-radius bends) instead of tight 90-degree bends makes pulling wires far easier. For runs over 50 feet, plan a pull box at the midpoint to halve the pull length.

Common Residential Conduit Projects

EV charger installs are the most common modern conduit project. A 50-amp Level 2 charger circuit typically uses 1-inch EMT in the garage and 1-inch PVC for any underground or exterior run. Plan $200 to $600 for the conduit and wire alone, plus $400 to $1,500 for licensed installation.

Garage subpanels for workshops or shop equipment use 100-amp feeders in 1-1/4 to 2-inch conduit, depending on wire size and distance. Outdoor lighting and outlets along walkways and patios use 1/2 or 3/4-inch PVC buried per code.

Permits and Inspections

Almost all conduit work tied to permanent home wiring requires a permit and inspection in US jurisdictions. The inspector checks burial depth, conductor sizing, grounding, bonding, and proper fitting use.

Skipping permits is a common mistake. If the work fails later or causes a fire, your homeowner’s insurance can deny coverage on uninspected wiring. Permits typically cost $50 to $200 — cheap insurance.

DIY vs. Hiring an Electrician

Conduit work itself is straightforward — bending EMT, gluing PVC, and pulling wire are skills most handy homeowners can learn from a weekend of YouTube and practice. The decision-making (sizing, code compliance, panel work) is where mistakes get expensive and dangerous.

For projects involving the main panel, service entrance, or unfamiliar code requirements, hire a licensed electrician. For pulling new conductors through existing conduit or extending a circuit you understand, DIY is reasonable with permits and inspection.

Frequently Asked Questions

What is the difference between EMT and PVC conduit? EMT is metal and rated for indoor exposed use. PVC is plastic and rated for direct burial and outdoor damp locations. Both are common in residential work.

How deep should conduit be buried? Residential branch circuits in PVC need 18-inch minimum burial depth. Direct-burial cable (UF-B) without conduit needs 24 inches. Local code may require deeper.

Do I need a permit for conduit wiring? Yes, almost always. Tied-in electrical work requires permits and inspections in nearly every US jurisdiction. Skip the permit and your insurance may deny claims.

Can I run Romex inside conduit? Generally no for full conduit runs. Romex (NM-B) is rated for in-wall use without conduit; using it inside conduit defeats the heat-dissipation design and can violate code. Use individual THHN conductors instead.