DIY pro tips: Electrical rough-in

A lot of people now prefer handling various aspects of home building themselves in an attempt to reduce labor costs. One of those aspects is what contractors call roughing in.

In construction parlance, rough-in refers to the stage of home construction when the basic structure has been built, and initial services like basic plumbing and electrical wires have also been completed. However, these services aren’t connected to outlets such as plumbing and light fixtures yet. 

At this stage of the construction, the roofing and walls are complete to an extent to protect the plumbing, electrical, and HVAC connections, but the drywall installation and other finishing touches are still pending. This allows building inspectors to check and approve the quality of the wiring and plumbing installations.

Electrical rough-in is something that even greenhorn home builders without too much experience can handle, just as long as they follow simple instructions. The use of flexible non-metallic cables, popularly called Romex, and plastic boxes make this an easy DIY project.

Keep in mind though that these tips are to only show you how to do a basic electrical rough-in wiring, and not the full-blown electrical installation using circuit designs and making connections to your circuit breakers and electrical panel. That requires the attention of a professional electrical contractor.

Don’t forget to get the necessary permit from your local building department before you begin, and to schedule an inspection after you’re done. 

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Tools 

The tools needed for this job are fairly simple. The basic tools used are a hammer, a cordless drill/driver, and a tape measure. In addition, you will need a special tool to cut and strip electrical wire. Use a ¾ inch spade bit to drill holes using your electric drill. You may also need to rent a heavy-duty right angle drill for larger jobs, along with a ¾ inch x 6-inch auger bit.

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The process

The first thing you need to do is mark box locations. To do this, begin by measuring and marking the center of each box. Mark the location of each box from the floor on the wall. This is usually 48 inches for switches and 12 inches for outlets. 

Mark the boxes with alphabets and letters so they’re easy to identify. For boxes that need to be positioned close to doors and windows, add 2×4 boxes to help position them properly.

1. Make sure you use the correct symbols to indicate the locations of switches, lights, and outlets.
2. Next, you will need to place the box on the framing member. To do this, place the box face flush with the wall covering material. Make sure the box is parallel to the framing member and nail the box to the framing.
3. There is a simple formula to calculate the minimum box size you require, according to the National Electrical Code. The formula is to add 1 for each hot and neutral wire entering the box, 1 for all the ground wires combined, 1 for any cable clamps you may use, and 2 for each switch or outlet, not counting lighting fixtures.

Multiplying the total by 2 for 14 gauge wires and 2.25 for 12 gauge wires will give you the minimum box size required in cubic inches.

1. Measure 8 inches above the boxes and drill holes into the framing using the ¾ inch bit. 
2. Use the right-angle drill to drill holes in the corner. Maintain a distance of at least 1 -¼ inches between the cable and the back face of the stud.
3. If that distance is not maintained, use a metal nail plate to cover the stud and protect the cable.
4. Straighten out around 12 feet of cable and thread through the holes from one box to the other. At every new box, strip the cable before pushing the conductors and about a ¼ inch of the sheathed cable into the box.

Then staple the cable and cut the end still connected to the coil.

1. When you need to fish electrical cables around corners, bend a sharp hook in them and push it through one end of the hole. Push a finger in through the other end, feel for the cable and guide it out.
2. When a cable reaches a box, grab it around where you estimate it to enter the box. Then cut it around 12 inches ahead of that point and strip all of it except one inch of sheathing.
3. Use a screwdriver to knock out holes in the box. Push in about a ¼ inch of sheathed cable and conductors into the box. Staple the cable about 8 inches from the box. Remember to keep the cable at least 1-1/4 of an inch away from the face of the framing.
4. Next, run the cable to your service panel from your completed circuits. Label the cables to show the location of the circuits. Then, hire an electrician to connect the circuits.
5. Cut and strip the wires, and then splice them with wire connectors.
6. Group and label the wires inside the electrical box so you can easily connect them after the drywalling is done. Your electrical rough-in is completed and ready for inspection.

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Costs

The average cost of an electrical rough-in is between $51 and $100, although the actual cost will depend on the size of the home and the number of materials needed. Expect this project to take you a few days to complete.

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Written by Narayan Shrouthy. January 6, 2022

Narayan is a content writer for Kukun. With experience in both content writing and editing, Narayan mixes his writing and love for reading with his passion for music. As an active musician, He aims to be a key player in Kukun's content experience.

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barbara.smith.lgtb@gmail.com(@barbara-smith-lgtbgmail-com)

One recommendation, never let your kid near for electrical contractors or family on electrical DIY projects, is distressing