In this article, you will learn about electrical scabs, which are used to push out an electrical box so it doesn’t interfere with another piece of equipment, like a door frame, kitchen cabinet, or get buried behind mechanical devices.
The goal is to always have the electrical plug or switch be accessible, and that the cover plate can easily go on during the electrical finishing stage of the job.
Don’t miss my electrical roughing-in series videos!
Note, sometimes Union electricians call “Non-union electricians” a scab, which is bad practice, and should never be repeated.
This article is referring to ELECTRICAL BOXING SCABS in the ROUGH-IN STAGE of the job. View my other electrical rough-in video series.
I worked non-union my whole electrical career, and learned well, with lots of opportunity. Union was not very popular where I lived, which made non-union the main way to find an electrical job.
What We Cover in this Article:
- What is an Electrical Scab (for Boxing)
- How Long to Make a Scab for Electrical Outlets
- Where to Use a Scab in Electrical Rough-In
- Different Materials to Use for a Scab
You need to know about:
- How many layers of drywall will go on a particular wall (so you know how far to stick out your switch box, after you break the box tabs off)
- What height to mount electrical boxes
- How easy the wire pull will be to the box BEFORE drilling holes for wires
What is an Electrical Scab (for Boxing)
In short, an electrical scab is used to push the box away to avoid it interfering with other equipment. This also makes sure we can have a clean finish and put the box cover plate on comfortably.
If your box was installed too close to another object, it either looks very tight, or you have to cut the cover plate to make it fit.. which is a clear sign of an amateur install!
Electrical scabs should be installed with screws for easy of install, and a strong hold.
Typically 8×3 wood screws are used, which I explain in my how to install a single gang electrical box, where you see I used 8×1 wood screws for the box, and 8×3 wood screws for the electrical scab.
You’re only allowed to install a maximum of TWO SCABS. If you need to push the box out further, you’ll want to either install another stud for your exact measurement, or you’ll need to do some fancy build-out (which takes way more time and effort).
How Long to Make a Scab for Electrical Outlets
I’ve found 10″ inch scabs for general switches and plugs is be the sweet spot to cut your scrap pieces of wood (scabs).
This allows you to move the electrical scab up and down without having to be perfect, and the electrical box ears usually fit nice every time!
For lights, you’ll always have to custom-cut the scab length EACH TIME, as joists and roof trusses can vary in distance a lot!
Pro-tip: For lights, it’s wise to make the scab 1/8″ longer than you need, so you can hit it into place and it won’t fall, then you can put your screws in!!
To be a wise electrician, BEFORE BOXING, you’ll want to cut a bunch of electrical scabs, and place them on the ground where electrical boxes need a scab.
It’s important to know that on some jobsites, scrap wood is HARD TO FIND because either the framers were very conservative on the amount of wood they used, or the general contractor cleaned up too early! (It’s a nightmare, as you need to push out the box, but can’t find any wood!)
So don’t make your scabs too long, otherwise you’ll waste wood, which can hurt you later on. If you go smaller than 10″ inches, I always found it finicky because sometimes you didn’t put the scab high enough, and the electrical box ears go above the scab.
Where to Use a Scab in Electrical Rough-In
Some BIG GOTCHAS are usually:
- Door Frames (Wood trim molding size can vary between 2-4 inches!! Make sure plugs, switches, and thermostats are away from the door frame!)
- Kitchen Cabinets (Make sure that your RANGE BOX or FRIDGE BOX do not line up IN-BETWEEN kitchen cabinets! You NEED TO KNOW the millwork layout before installing electrical boxes!)
- Mechanical Equipment (You must know where heaters, pumps or mechanical devices are to be installed, so that you can easily access your electrical box!)
Different Materials to Use for a Scab
In this article, I’m talking to you from a wood frame setting.
However, commercial electricians often use METAL STUDS. These metal studs can very in gauge (thickness), so try to find THIN GAUGE METAL, if using metal scabs, to make life much easier with TIN SNIPS!
Metal boxing requires different skills and time. Also, you’re cutting metal which can be VERY SHARP, and you have to learn how to cut and fold metal for very powerful scabs.
Conclusion: What is an Electrical Scab
I hope that helps you understand that an electrical scab is used to push out an electrical box to prevent it from being in the way of another piece of equipment, and that we can comfortably install our cover plate.
Please view my electrical roughing-in series for more videos!
You may like to have a little laugh with funny electrician jokes, too 😂