If you do a lot of work around the house or consider yourself a do-it-yourselfer, at some point, you may find yourself needing to install or re-locate an electrical box in a wall.
Whether you are renovating a room or doing a complete house remodel, electrical boxes must be installed properly for your lights to shine and your electrical devices to run once the work is complete.
Electrical boxes should be mounted so that the outer edges are recessed no more than one-quarter inch (6 mm) from the drywall surface. The reason is not for aesthetics but to minimize the risk of arcing and electrical fires for safety.
Although standard drywall made from gypsum (the most common of drywall material) is reasonably fire-resistant, it falls short of actually being fire-proof. (Source: Angie’s List – Solution Center)
As such, certain precautions must be taken when installing electrical boxes in walls, and this includes mounting them so that they are flush with the drywall surface. This is not only good practice but in the U.S., it is the national electrical standard.
Should Electrical Boxes Be Installed Flush with Drywall?
Electrical boxes are designed to safely contain the electrical wiring for things like electrical outlets and light switches. They can vary in size and shape but are most commonly configured for one (single-gang) or two (double-gang) electrical hookups.
As such, electrical boxes serve a vital function as far as electrical and fire safety in a home or structure. (Source: This Old House)
According to Article 314.20 of the National Electrical Code, electrical boxes that are installed in walls or ceilings with surface materials consisting of “concrete, tile, gypsum, plaster, or other non-combustible material” must be positioned such that the forward (outer) edge of the box is recessed no more than one-quarter inch.
In the case of combustible materials like wood paneling, the edges of the electrical box must be completely flush with the wall or ceiling surface. (Source: National Electrical Contractors Association – NECA)
What is the National Electrical Code?
The National Electrical Code (NEC) is the “official” rulebook for the United States (and much of the world) as far as establishing and maintaining electrical safety standards. The NEC covers virtually everything pertaining to residential, commercial, and industrial electrical applications.
Also known as the NFPA 70, the NEC is published by the National Fire Protection Association, and updates are released every three years. The latest version is the 2020 NEC, and four states in the U.S. have updated their regulations accordingly.
Still, the overwhelming majority of states (31 out of 50) have electrical codes based on the 2017 version of the NEC, while the remaining states rely on even older versions. (Source: National Fire Protection Association – NFPA)
How to Install Electrical Boxes to be Flush with Drywall
When installing electrical boxes, they are typically mounted to studs or joists for greater stability. This phase of the work is done before the drywall is put up, so proper positioning is important so that when the drywall is installed, the edges of the electrical box end up being flush with the drywall surface.
Fortunately, there are a couple of simple tips and steps that take the guesswork out of installing electrical boxes at the proper wall depth:
- The standard thickness of drywall is either 3/8” or 1/2″ (1/4” and 5/8” drywalls are also available, but these are non-standard thicknesses).
- With the electrical box positioned, but not yet fastened to a stud or joist, hold a piece of scrap drywall of the same thickness as what will be installed, and lay it against the side of the electrical box.
- Adjust the depth of the electrical box against the stud or joist so that the outer edges are flush with the piece of drywall when it is held against the side of the box.
- Once the correct positioning is verified, you can proceed with fastening the electrical box to the stud or joist permanently.
Many electrical boxes available today come with depth gauges built into them, so you can quickly determine the proper position of the box and fasten them in short order without going through the additional step of measuring depth with a piece of drywall. (Source: Better Homes & Gardens)
One thing to consider as far as determining the proper depth of electrical boxes is whether additional material will be applied on top of the drywall. For instance, decorative tile, adhesive faux tile panels, and similar wall coverings will add additional thickness to the underlying drywall.
Therefore, if you plan to add additional material to your wall, the edges of your electrical box must protrude further out than the drywall thickness to account for the additional wall material.
Why Does Installing Electrical Boxes Flush with Drywall Matter?
If you are wondering why the proper installation of electrical boxes matters so much, the reason is that faulty electrical work is a contributing factor to thousands of house fires each year, causing billions of dollars of damages and losses, and tragically, hundreds of deaths.
The data is sobering and highlights the ongoing need for rigid electrical standards and strict enforcement of electrical codes.
Here are a few figures to consider:
- Each year, over 50,000 fires are caused by electrical problems and are associated with nearly 500 deaths, over 1,400 injuries, and over $1.3 billion in property damage.
- The third leading cause of house fires is electrical distribution systems.
- Over 28,000 house fires every year are caused by electrical arcing.
- Faulty electrical receptacles cause over 5,300 fires each year.
The key takeaway here as far as installing electrical boxes is that, by setting them flush with the drywall surface, the possibility of arcing from the wires to the wall substrate is minimized, which reduces the risk of an electrical fire.
This is particularly crucial when flammable materials are used for wall surfaces, such as wood paneling or synthetic materials like faux-tile decals, that are applied on top of the drywall.
Is Your Electrical Box Not Flush with Your Drywall?
Sometimes, even though you do everything by-the-book, things do not always work out as intended. And when it comes to do-it-yourself home renovations, they seldom do.
In the case of electrical boxes, if the drywall goes up and you find that an electrical box is recessed more than the quarter-inch that is allowed under the National Electrical Code, there is no need to panic.
This happens more often than you would think.
It happens so often that there is a readily available remedy just for such instances, and it is known as an electrical box extender.
Purchase an electrical box extender online (link to Amazon)
This inexpensive gadget acts like an electrical box that slides inside the actual (and improperly installed) electrical box, allowing its edge to be installed flush with the drywall surface while still safely housing the electrical wiring.
This YouTube video outlines how to use electrical box extenders:
Having a few electrical box extenders handy would definitely qualify as a pro move, especially on a large project. (Source: Mike Holt – General Electrical Forum)
Performing your home’s electrical work yourself can be done safely and with satisfactory results as long as you are committed to learning the proper techniques.
With electrical boxes, planning so the edges are flush, or no more than one-quarter inch recessed from the wall surface, will ensure that your work is up to code. It will also result in a finished job that has been completed with electrical safety in mind.
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As a homeowner, I am constantly experimenting with making the structure of my house more energy-efficient, eliminating pests, and taking on DIY home improvement projects. Over the past two decades, my family has rehabbed houses and contracted new home builds and I’ve learned a lot along the way. I share my hard-learned lessons so that you can save time and money by not repeating my mistakes.