Residential Wiring - New Construction Rough-In

A new single-family house is wired in three stages: rough-in, inspection, and trim. Rough-in is where the real craft lives. Everything you hide behind drywall has to be right, because once the tapers show up you are not getting back in without a saw. This guide walks you through the rough-in sequence from plans to panel labels - NM-B cable, staples, box fill, mounting heights, GFCI/AFCI zones, and the small habits that keep your work off the inspector's failure list.

The Three Stages

| Stage        | When                                  | What You Do                                  |
|--------------|---------------------------------------|----------------------------------------------|
| Rough-in     | Frame done, before drywall            | Boxes, cable runs, staples, nail plates, labels |
| Inspection   | Right after rough-in, before drywall  | Inspector verifies box fill, staples, zones |
| Trim         | After paint                           | Devices, fixtures, panel makeup, testing     |

The rough-in inspection is the gate. Nothing gets covered until the inspector signs it. The drywall crew will not hang until you clear. So the pressure is real - rough it right the first time, because opening a wall on a fail is ugly.

Plans and Prints

Before the first cable goes up, somebody reads the plans. On a small residential job the journeyman usually does this, but you should be reading along.

• Electrical floor plan - Shows device locations (receptacles, switches, lights), circuit numbers, homeruns to the panel.
• Panel schedule - Lists every circuit, breaker size, wire size, and description.
• General notes - Jurisdictional amendments, special circuits (EV charger, hot tub, solar), smoke/CO detector requirements.
• Specs - Brand requirements for devices, boxes, panels.

If something on the plan is wrong (receptacle right where a cabinet is going, switch in a door swing, panel in a closet where code forbids it), catch it before you run cable. Raise it to the journeyman; do not just move the box on your own.

The Panel-to-Device Path

Every circuit follows the same logical path:

1. Branch-circuit breaker at the panel.
2. Homerun cable from the panel to the first box on the circuit.
3. "Travelers" between boxes on the same circuit.
4. Final box for the last device on the circuit.

You will run homeruns first (pulling from each circuit's first box back to the panel), then daisy-chain the rest. A clean homerun stack at the panel makes trim-out five times faster.

NM-B Cable Types and Sizing

NM-B (non-metallic sheathed, dry/damp locations, 90 deg C insulation rated to 60 deg C ampacity) is the residential default - what people call "Romex." Commit these wire-to-circuit pairings to memory:

| Cable     | Copper Ampacity | Typical Circuit          |
|-----------|-----------------|--------------------------|
| 14/2      | 15 A            | Lighting, general 15A    |
| 14/3      | 15 A            | 3-way switched lighting  |
| 12/2      | 20 A            | Kitchen, bath, outdoor, small appliance |
| 12/3      | 20 A            | 3-way 20A, shared neutral |
| 10/3      | 30 A            | Electric dryer           |
| 8/3       | 40 A            | Electric range (typical) |
| 6/3       | 55 A            | Sub-panel feeder, large range |
| 4/3 or 2/3| 70+ A           | Main service, large sub-panel |

The number before the slash is the wire gauge (AWG). The number after is the count of current-carrying conductors plus a bare equipment grounding conductor (EGC). So 12/2 is two 12 AWG insulated conductors (hot and neutral) plus one bare 12 AWG ground.

Never install a circuit where the wire is too small for the breaker. The breaker protects the wire - a 20A breaker on 14 AWG is a fire hazard; a 15A breaker on 12 AWG is legal but wasteful.

Running Cable

Drill Holes Center of Stud

Every hole drilled through a stud goes through the center. Why:

• A hole within 1.25 inches of the stud edge is too close to the finished wall surface - a drywall screw or a picture nail can hit it.
• Centered holes keep the wood structure strong.

If a hole ends up less than 1.25 inches from an edge (ripping around a duct, routing around a window header), install a nail plate (metal stud guard) over the hole on the face where the cable passes. Nail plates prevent drywall and finish screws from piercing the cable.

Drill with a 3/4 inch or 7/8 inch auger or self-feed bit for single-cable runs. Pull multiple cables together through one hole where possible (up to four cables in a 7/8 inch hole typically; check local amendments for derating rules).

Run Through Top Plates and Bottom Plates

Vertical runs from an outlet up to a light or switch go up through the top plate. If the wall has two stacked top plates (almost always) and the run continues to the attic, drill through both plates in line. Nail plates on both faces if within 1.25 inches of the face.

Staples - the Rules

NM-B cable must be secured by staples (or listed cable clamps) per NEC 334.30:

• Within 8 inches of every single-gang plastic box (without internal clamps). A nail-on plastic box with integrated clamps allows 12 inches.
• Within 12 inches of every metal box or box with its own clamp.
• Every 4.5 feet along the run.
• Listed staples only. Not fence staples. Not insulated staples driven so far they crush the sheathing - staples sit flush, not tight.

Staple through the flat side of the cable (the wide dimension) - staples across the narrow edge pinch and can damage the conductors.

Cable Protection Between Boxes

Cable running in an attic or crawl space parallel to framing members must be secured every 4.5 feet. Cable running across joists (perpendicular) in an accessible attic within 7 feet of the scuttle hole needs a running board (a board wide enough to protect the cable from being walked on). In unfinished basements, cable 6 AWG and smaller running across joists must be routed through holes or along running boards.

Box Fill Calculations

Box fill is the part of the rough that trips up more apprentices than any other single topic, because it looks like math but is really just bookkeeping. NEC 314.16 is the reference.

Start with the box's cubic-inch rating (stamped on the box, e.g., 18 cu-in for a typical plastic single-gang).

Deduct for each item that enters the box:

| Item                             | Count as               |
|----------------------------------|------------------------|
| Each 14 AWG insulated conductor  | 2.00 cu-in             |
| Each 12 AWG insulated conductor  | 2.25 cu-in             |
| Each 10 AWG insulated conductor  | 2.50 cu-in             |
| Each 8 AWG insulated conductor   | 3.00 cu-in             |
| Each device (yoke)               | 2x largest conductor in box |
| Internal cable clamps (one or more)| 1x largest conductor    |
| All EGCs (grounds) combined      | 1x largest conductor    |

Key rules most apprentices miss:

• Yoke counts as 2 conductors of the largest size in the box. A single receptacle on 14 AWG counts as 2 x 2.00 = 4.00 cu-in.
• All grounds combined count as one conductor. Not one per ground.
• Clamps inside the box count as one conductor total - not one per clamp.
• Conductors originating and terminating in the box count once. A pigtail made inside the box and not entering/leaving does not count.
• Wire nuts and push-in connectors do not count.

Worked example: plastic single-gang box, 18 cu-in. Two 14/2 cables enter (one home, one going on). Internal clamps. One duplex receptacle.

• 4 x 14 AWG conductors (2 hots + 2 neutrals) = 4 x 2.00 = 8.00 cu-in
• All grounds combined (2 bare 14 AWG grounds count as one 14 AWG) = 2.00 cu-in
• Internal clamp(s) = 1 x 14 AWG = 2.00 cu-in
• Yoke (receptacle) = 2 x 14 AWG = 4.00 cu-in
• Total = 8 + 2 + 2 + 4 = 16.00 cu-in, under the 18 cu-in box. Legal.

Add a switch and another cable? You run over and have to upsize to a 22.5 cu-in box.

Box Mounting

Box faces sit proud of the stud by the thickness of the finished wall material - typically 1/2 inch for standard drywall, 5/8 inch in garage walls or where fire-rated board is called for. The cover plate must sit flush to the finished wall surface; most plastic nail-on boxes have a 1/2 inch plaster ring built in.

Level the box before you nail. A box that is 1/4 inch tilted looks tilted for the next 50 years.

Receptacle Heights

• General rooms - Centerline 12-18 inches off the finished floor. Most shops spec 15 inches center as a standard.
• Kitchen counter - Centerline 42-46 inches off the finished floor (to put the receptacle above the backsplash). Typical is 44 inches center.
• Bathroom - Next to the sink, 38-42 inches is typical. Confirm with the plans.
• Garage - Same 12-18 inches unless spec says otherwise.
• Outdoor / damp - Spec-driven, but usually 12-18 inches above finished grade with weatherproof in-use cover.

Switch Heights

• Standard switch - 48 inches to the top of the box (the "top of the switch plate" is a common spec - confirm whether the plan is calling out top of box or centerline).
• ADA residential - 48 inches maximum centerline.

Smoke and CO Detector Boxes

• On the ceiling - Smoke detectors centered 4+ inches from a wall (or follow manufacturer). In a bedroom, one inside, one right outside in the hall.
• CO detectors - One on every floor with a fuel-burning appliance or attached garage, and outside each sleeping area. Hardwired with battery backup, interconnected (the 3-conductor leg between them).

GFCI and AFCI Zones - NEC 2023

Two overlapping protection systems. Check which version of the NEC your jurisdiction has adopted.

GFCI (Ground-Fault Circuit Interrupter) - NEC 210.8

Required in every location where water or dampness increases the shock hazard:

• Kitchens - All counter receptacles. Dishwasher now requires GFCI protection.
• Bathrooms - All receptacles.
• Garages and accessory buildings.
• Outdoors (all locations readily accessible).
• Laundry areas.
• Basements (finished and unfinished).
• Crawl spaces at or below grade.
• Within 6 ft of a sink (laundry room, wet bar, etc.).
• Near pools, hot tubs, and fountains (specific distances per article 680).

GFCI can be at the breaker (protects whole circuit) or at the first receptacle (protects that and downstream). Breaker-type is cleaner and expected on most new work.

AFCI (Arc-Fault Circuit Interrupter) - NEC 210.12

Required on all 120V, 15A and 20A branch circuits supplying outlets or devices in:

• Bedrooms
• Living rooms
• Family rooms
• Dining rooms
• Halls and hallways
• Closets
• Laundry areas
• Sunrooms
• Kitchens (some NEC editions; check jurisdiction)

"Combination-type AFCI" is the standard - handles both series and parallel arcs. Where GFCI is also required (kitchens, laundry), a dual-function breaker (DFCI - AFCI/GFCI combo) covers both.

Dedicated Circuits

Some loads must be on their own circuit (not shared with anything else):

• Kitchen small-appliance branch circuits - Minimum 2 x 20A circuits feeding countertop receptacles. No lighting, no refrigerator-only circuit mandate but most jobs dedicate one.
• Bathroom - Minimum 20A circuit feeding only bathroom receptacles. One bath circuit may serve multiple bathrooms, OR a single bath's circuit may serve lighting and fan - but not both (serves either multiple bath outlets, or all loads of a single bath). Read 210.11(C)(3) carefully.
• Laundry - Dedicated 20A circuit.
• Dishwasher, disposal, microwave - Individual circuits per spec.
• Range, dryer, water heater, HVAC, EV charger - Individual per-device circuits.

Wet/Damp Locations

• Damp location (covered porch, under a roof) - Weatherproof cover when cover is closed (WP).
• Wet location (exposed to weather, outdoor receptacle) - Weatherproof cover when in use (WP-IU) - the bubble cover. Use outdoor-rated box (cast alum or approved PVC with gaskets) and weather-resistant (WR) receptacles.

Pigtails vs. Backstabs

At every device, you have two choices for how conductors land:

• Pigtail - All incoming conductors are joined with a wire nut, and a 6-inch pigtail of the same gauge lands on the device terminal. Pros: device removal does not break the downstream circuit, terminal torque on a single conductor is reliable.
• Backstab (push-in) - Push the conductor into the rear hole of the device. Pros: fast. Cons: these holes fail under vibration, under heat, and over time. Many shops forbid backstabs on new work.
• Screw terminal (side-wired) - Loop the conductor clockwise around the terminal screw, torque to spec. Reliable. Allowed on virtually all jobs.

Pigtails and side-wiring are the professional default. Backstabs on 15A/20A receptacles are where apprentices learn why pigtails exist - when the first floor of a house has eight receptacles wired downstream of a backstabbed outlet and one fails, the homeowner's whole living room goes dark.

Splicing

All splices happen inside boxes. Methods:

• Wire nuts - Twist conductors clockwise 3-5 twists in advance with linemans (no pre-twist on some small-gauge, shop preference), then apply the nut. Tug each conductor; anything that pulls is a redo.
• Push-in (WAGO / Ideal Lever-Nut) - Fast, reliable, reusable. Increasingly popular. Read the listing for the gauge range.
• Crimp sleeves - Less common in residential; used on some service and equipment grounds.

Whatever the method, the splice goes inside a covered box - never behind drywall, never in a ceiling cavity, never in an attic without a junction box.

Labeling at the Panel

Every homerun cable gets labeled at the panel end before drywall. Sharpie on a strip of masking tape or a wrap-around label. Typical format:

• Circuit number (assigned from the panel schedule)
• Room or device identifier (KITCHEN SA1, MBED RECEP, LAUNDRY)
• Homeowner-friendly labels will get finalized at trim; rough labels are for the rough inspector and for the trim electrician to pick up the circuits fast.

An unlabeled stack of 30 homerun cables at trim-out is a four-hour problem that five minutes of Sharpie at rough-in would have prevented.

The Rough-In Inspection

When the inspector arrives, they are checking:

• All boxes installed, level, at correct height, correct cubic-inch rating for the fill.
• All cables stapled per 334.30 - within 8 inches of plastic single-gang boxes, every 4.5 ft.
• All cables through drilled holes or behind nail plates where within 1.25 inches of a stud edge.
• Wet/damp location boxes and fittings correct.
• Dedicated circuits to fixed appliances.
• GFCI and AFCI protection per zones.
• Panel grounding electrode connections (if the panel is in before drywall).
• Smoke/CO detector boxes at correct locations, interconnected traveler present.

A clean rough, with homeruns labeled and every box plumbed, walks out in a 20-minute inspection. A messy rough with a dozen small misses becomes an all-day back-and-forth.

Common Failures

• Staple tight enough to squash the cable. Back it off. Staples sit against the sheathing, not crushing it.
• Cable through a stud less than 1.25 inches from the face, no nail plate. Automatic fail.
• Over-filled box. Count again. Upsize if needed.
• Missing AFCI. Hallway and bedroom circuits are a common miss.
• Dishwasher not on GFCI (NEC 2020+). Catches people who learned on older code cycles.
• Unterminated hots left bare inside a box. Every conductor must be wire-nutted or on a device. No exposed copper in a covered box.

Day 1 Checklist

• Drill, 3/4 and 7/8 inch auger/self-feed bit
• NM-B cable to the sizes in the plans
• Cable staples (plastic-insulated, listed)
• Nail plates, a stack of them
• Plastic nail-on boxes, single and multi-gang, mud rings for metal boxes if used
• Wire nuts and/or push-in connectors, assorted
• Sharpie and masking tape for labeling
• Plans and panel schedule

Expert Tips

• "Rough as if the drywall is going up tomorrow, because it is." No reopening after tape.
• "Label every homerun before lunch on the last rough day." Future-you at trim-out will thank you.
• "Count conductors twice for box fill, not once." One mis-count becomes a failed inspection.
• "Pigtails on every device, every time." Shop will teach you the same habit.
• "When the plan says 44 inches to counter receptacle center, it means 44 inches off the finished floor - not the subfloor." Subtract the flooring thickness.