Residential Wiring - New Construction Rough-In

A new house is wired in stages. Rough-in comes after framing and before insulation and drywall, and it is where almost all the wiring goes in. Everything you hide in a wall has to be right, because getting back to it later means cutting drywall. This guide covers the physical work of rough-in, in the order you do it, and what an inspector looks for at the end.

What You Will Be Able to Do

• Plan a rough-in from the plans and walk the house before you drill.
• Set boxes at the right height and depth for the finished wall.
• Drill framing and protect cable where it runs close to a surface.
• Secure NM cable to code in walls, attics and basements.
• Make up boxes so they are ready for trim, and pass the rough-in inspection.

Section numbers are from the National Electrical Code (NEC). The 2026 edition renumbered some of them, and your state or city may enforce an older edition with local changes. Check before you start.

The Three Stages

The rough-in inspection is the gate. Insulation and drywall crews cannot start until you pass, so a failure holds up other trades.

Before You Drill

Walk the house with the plans. Mark every box location on the studs with a lumber crayon, room by room. Look for these conflicts:

• A receptacle where a cabinet or tub will go.
• A switch behind a door swing.
• A box in the path of a duct or drain.
• A panel in a clothes closet or bathroom, where code does not allow it.
• A panel without clear working space, which is usually 30 inches wide, 36 inches deep and 6-1/2 feet high.

Tell the journeyman about any problem. Do not move a required box on your own. Coordinate with the plumbers and HVAC crew, because whoever gets there first takes the space, and ducts cannot bend around your cable.

Identify the circuits and how each one gets back to the panel. The cable from the panel to the first box is called the home run. Plan runs to keep them short and to avoid crossing framing more than needed.

Setting Boxes

Depth

The front edge of a box must end up in the right place relative to the finished wall. Under NEC 314.20, in a noncombustible surface such as drywall, the box may be set back no more than 1/4 inch. In a combustible surface such as wood paneling, the box must be flush or stick out. Find out the wall finish first. Half-inch drywall is standard, 5/8 inch is common in garages and on fire-rated walls, and tile adds more. Most nail-on boxes have depth gauges molded into the side.

Height

Heights are set by the plans and local practice. Measure from the finished floor, not the subfloor. Allow for tile or hardwood that has not been installed yet. A laser or a story pole makes every box in the house match.

Level each box before you fasten it. Make sure gangs line up in a row.

Special Boxes

• Ceiling fans: use a box listed for fan support, secured to the framing or a listed brace. A standard light box is not rated to carry a moving fan.
• Heavy fixtures: a box must be listed for the weight, or the fixture must be supported separately.
• Outdoor boxes: use the plans and a weatherproof type for the location.
• Box size: count the box fill before you commit to a size. Deeper boxes make GFCI and smart devices easier to install.

Drilling the Framing

Wear eye protection. Use a right-angle drill with an auger or self-feed bit, and hold on. These drills can twist hard when the bit binds, and that can break a wrist or throw you off a ladder.

Warning: Stop and check before you drill or notch. Cutting a structural member beyond its limits weakens the building. Most building codes limit hole and notch sizes in studs and joists, and engineered lumber has its own rules. Never cut trusses or engineered joists without approval.

Drill near the center of the stud, about at the same height along a wall so the cable runs straight. A straight run also makes it easy to pull.

The 1-1/4 inch rule. A drywall screw or trim nail reaches about 1-1/4 inches into a stud. So cable in a hole must be at least 1-1/4 inches from the nearest edge. If it is closer, you must cover the framing with a steel plate at least 1/16 inch thick, long enough to cover the area. This rule is in NEC 300.4 in the 2023 edition and moved to 300.6 in the 2026 edition. It also applies to cable in a notch, and to cable lying in a groove in the wood.

Metal studs need a listed grommet or bushing at each hole, so the sharp edge cannot cut the jacket.

Running Cable

Unroll cable from the center of the coil, or use a reel, to avoid twists and kinks. Pull with steady pressure. If it stops, go find the snag. Do not yank it, because a damaged jacket fails inspection and a nicked conductor is hidden in the wall forever.

Leave enough cable at each box. The NEC requires at least 6 inches of free conductor from where it emerges in the box, reaching at least 3 inches past the box opening. Most electricians leave 8 to 12 inches, then trim. At the panel, leave enough to reach the far side of the panel, plus extra for neat routing.

Use a cable bend radius of at least 5 times the cable diameter. Avoid sharp folds at corners.

Bundled cables create heat. If you run several NM cables tightly through the same bored hole sealed with fire caulk or insulation, ampacity adjustment rules can apply. Ask the journeyman how the shop handles this, and do not stack more than local practice allows.

Do not run NM cable through air ducts or in other places listed as not permitted, and keep it away from hot flues. Some cities do not allow NM at all, so confirm the wiring method on your job.

Securing Cable

NEC 334.30 requires NM cable to be supported and secured. A nail-on or strap-type staple listed for the cable does the job.

The 8-inch rule comes from NEC 314.17 and applies only to small nonmetallic boxes that do not have internal clamps. In those boxes, the cable sheath must also extend at least 1/4 inch into the box, past the knockout, so the conductors do not rub on the edge.

Tips for stapling:

• Drive the staple until it holds the cable without squeezing it. A crushed jacket can fail inspection, and it can damage the conductors.
• Keep the flat side of the cable against the framing.
• Do not put more cables under one staple than it is listed for.
• Cable through bored holes in framing already counts as supported at those points, when the holes are no more than 4-1/2 feet apart.

Attics

Cable across the top of joists in an accessible attic needs protection so that it is not stepped on. Under NEC 320.23, which NM cable follows, guard strips at least as high as the cable are required in these places:

• Within 6 feet of the scuttle hole, if there are no permanent stairs or ladders.
• Across the whole area, if the attic is reached by permanent stairs or a ladder.

Running along the sides of joists, or through bored holes, avoids the issue.

Basements and Crawl Spaces

In unfinished basements, cables smaller than two 6 AWG or three 8 AWG conductors cannot be run across the bottom of joists unless they follow a running board. Drill through the joists or use a running board. Where cable drops down a bare wall, it needs protection from physical damage, such as conduit.

Making Up the Boxes

At rough-in, you normally make up the grounds and neutrals, so all that remains at trim is connecting devices.

1. Strip the outer jacket, leaving the sheath inside the box as required.
2. Splice all the grounds together, with a pigtail for the device. In a metal box, also bond to the green screw on the box.
3. Splice neutrals that are not going to a device, and leave a pigtail.
4. Fold conductors neatly to the back of the box, with hots left long.
5. Put a mark or tape on any switch leg or traveler.

Use twist-on connectors sized for the wires, or lever-type connectors listed for the gauge. Tug each conductor after you make the splice. A wire that slips will fail later when no one can see it.

Every splice must be in a box. Boxes must stay accessible, so no box can be buried behind drywall.

Labeling

Mark each home run at the panel end, before the walls close up. Use a marker on tape or a tag. Write the circuit number and the room or load, such as "12 KITCHEN SA1." Labels at this stage are for the inspector and the trim crew. An unlabeled stack of cables can take hours to sort out.

The Rough Inspection

Self-inspect before you call. The inspector usually checks these items:

• Boxes at the right depth, secured and the right size for the fill.
• Cable secured at the required distances.
• Nail plates wherever cable is close to a surface.
• Grounds spliced and bonded in each box.
• Required circuits present, including kitchen, bath and laundry.
• Fan-rated boxes and listed supports where needed.
• Smoke alarm boxes in the right places.
• Fire blocking restored where you drilled fire-rated assemblies.

Be on site if you can. If something fails, fix the problem and call for a recheck. Take photos of each wall before it closes. They are useful when someone needs to find a stud or a cable later.

Common Failures

Check Your Understanding

1. A cabinet maker tells you the kitchen wall will get 1/2 inch drywall and 3/8 inch tile. How do you set the boxes?

Set them so the front edge ends up at the finished tile surface, or no more than 1/4 inch behind it, which means allowing for both layers.

2. A hole has to go 1 inch from the face of a stud to clear a pipe. What do you do?

Install a steel nail plate at least 1/16 inch thick over the area on that face, because the hole is less than 1-1/4 inches from the edge.

3. You are running cable to a single-gang plastic box with no clamps. Where is your last staple?

Within 8 inches of the box, with the jacket extending at least 1/4 inch into the box.

4. Your staple gun has dented the cable jacket. Can you leave it?

No. Remove that staple and check the cable for damage. A crushed sheath can be cited, and it can hurt the conductors. Replace the section if the damage goes through the jacket.

5. The attic has a pull-down ladder. Do cables on top of the joists need guard strips?

A permanently installed ladder means protection is needed across the attic. Run the cables along the joists, or use guard strips.

Key Takeaways

• Walk the job with the plans, and resolve conflicts before you drill.
• Set boxes for the finished wall surface, measured from the finished floor.
• Cable in framing must be 1-1/4 inches from the edge, or protected with a steel plate.
• Secure NM every 4-1/2 feet and within 12 inches of a box, or 8 inches at a single-gang nonmetallic box with no clamp.
• All splices go in accessible boxes, and every conductor should pull tight.
• Label home runs and self-inspect before you call for the inspector.