In this article, you will learn best practices for mounting and installing electrical boxes. This is a part of my electrical roughing-in series.
For homeowners doing DIY electrical, there is no “standard electrical box height measurements”, there are CODE MINIMUM heights, but generally, 48″ to top of switch and 16″ to top of plug is a good place to start.
If prints don’t state switch heights, I like to do the “pretend switch test”. Walk into the room, pretend to turn the switch on, and that will give you an idea of where to mount your switch heights. It really works! 😂
What We Cover in this Article:
- Important Things to Know BEFORE Installing Electrical Boxes
- First Determine your Box Mounting Heights
- Always Consider Drywall Depth (Being in is Better than Out)
- Does the Layout Make Sense?
- Recommended Boxing Tips for an Awesome Workflow
Important Things to Know BEFORE Installing Electrical Boxes
Over your electrical career (whether you’re an apprentice or journeyman), you’ll work with quite a few foreman (a foreman is the one running the job).
Each foreman has their own way of doing things, and sometimes they don’t understand the little tricks to make life easier for electricians (they just want the job done FAST.. no matter what it takes).
So listen close when I say A GOOD ROUGH-IN MAKES FOR AN EASY FINISH!
(Finishing is once dry wall and paint is on the walls. We electricians then install our plugs, switches, lights, circuit breakers, and make sure the right voltage is at each device!)
So let’s get started:
Where to Find Box Mounting Height Information
You must make sure your ground is A.F.F. (Above Finished Floor!)
In other words, are they going to pour concrete and change the floor height? You NEED to know the EXACT height of the floor to find your “Above Finished Floor” height. Fight for this answer!!
WATCH OUT: Ceiling Heights Will Get You!
Be very catious of ceiling heights in a commercial building. These ceiling heights are given in our architectural prints.
If you don’t look at ceiling heights, your electrical box may end up above the ceiling, or even more embarrassing, you may see only half your electrical box, because the ceiling is in the center of it! 😂
The reason ceiling heights may be lower then the actual ceiling is beause equipment is run in the ceiling like electrical pipes, mechanical pipes (plumbing and sprinklers), and HVAC ducts. If it’s a hard ceiling (drywall), you need to have access panels for electrical boxes. If it’s a T-Bar ceiling, you can just pop-up a ceiling tile to access things.
Access panels are expensive, and don’t look good, so you should always try to avoid them (by installing the box in an easy to access area.. but if you can’t, you’ll need an “access panel”. Now you know!
Top of Box is your Measurement!
In short, use the TOP OF BOX when installing your electrical boxes and measuring heights!
I can’t tell you how annoying it is when a foreman says, “Mount electrical boxes to bottom of box”. Have you ever tried to install a plug to the bottom of the box? You have to get on your knees, lean over, and even then, you can barely see if you’re lined up.. it’s horrible!
What about center of box? You’re going to have VERY INCONSISTENT box heights because it’s so hard to get EXACTLY CENTER each time.
Also, your hand will block your view if you meausre to bottom or center of box.. it’s just not a good way to work.
TOP OF BOX is easy to see, easy to remain consistent, and makes everyone happy on the jobsite 🙂
Measure to SCREW HOLE on Serious Electrical Boxes
There’s two types of situations you’ll run into when mounting boxes..
- General Plugs/Switches
- Serious Plugs/Switches
General Plugs/Switches don’t need to be EXACT. Because they aren’t very close to each other, it’s hard to see if a plug or switch is out a 1/4″.
Serious Plugs/Switches must be within a 1/16″!! (Even that’s noticable to a trained eye). I’m 100% serious, and that’s why it’s worth talking about.
For SERIOUS BOX HEIGHTS, you’ll want to make sure to use a laser, or, measure to the SCREW HOLE on the box.
An example of a SERIOUS BOX SITUATION would be plugs in the kitchen’s backsplash where there’s groutlines! If you are off by an 1/8″, grout-lines create a visual line to compare our boxes to, and box height becomes VERY noticable!
What’s Your Wall Depth or Ceiling Depth?
When you’re new to construction, you’re not aware of FIRE RATING.
In a multi-dwelling building (condo/apartment), fire rating is VERY IMPORTANT because someone else can cause a fire in another suite. That is why condos have a dedicated fire alarm system and sprinkler system!
We electricians must pay close attention to drywall depth, otherwise electrical boxes get burried BEHIND the wall!
(We are only allowed a little gap according to electrical code in the drywall to our electrical box, and if there’s too big of gap, we must use a “box insert”… I used to call these box inserts “oopsies” because someone didn’t look at the prints).
How do you find wall depth and ceiling depth?
You use architectural prints! (Every job will have them. They share dry-wall depth, ceiling height, ground work, and so much valuable information on the building!)
For example, they sometimes use a layer of plywood then drywall. Plywood is not fire rating, but to keep the building strong. Drywall TYPE-X is for fire rating. However, plywood still adds thickness to the wall, which we have to take into account to push our box out further!
You must look for WHAT SIZE of dry wall. Is it 1/2″ or 5/8″ ?
Do You Need to Use an Electrical Scab?
An electrical scab pushes out the box away from a door frame for example.
If your box is TOO CLOSE to certain devices, it will be hard to put on the cover plate, and make the install look good.
We use Electrical Scabs to nudge our box over.
And now you know the core basics of mounting electrical boxes.. let’s cover them a bit more general now, and that’s it for this article!:
FIRST DETERMINE YOUR BOX MOUNTING HEIGHTS
Even before you consider installing a box while you’re in the rough-in stage, it’s absolutely crucial to know your mounting heights.
It’s crazy how many times I’ve had to go back because a foreman got the mounting heights wrong.
This really eats up time on a job fixing simple tasks like this.
So know your numbers!
In a condo, for example, we’d have to know heights for:
- Kitchen Counter Plugs
- Fridge Plug
- Fire Alarm Devices
- Emergency Heads (Remote Heads)
In addition to mounting heights, you also have to be aware of your ceiling heights, too, as you don’t want devices above the ceiling or too close to the ceiling!
And, besides heights, we also have to know of any special rules.
A common special rule would be party walls, for example! (A party wall is a wall that is shared with a separate suite. Boxes typically have to be a full stud-space apart and cannot be a data ring – a single-gang box must be installed instead. Party walls are in shared-unit buildings.)
Trust me, it’s important to get all these details up front. Otherwise, I guarantee you’re going to waste time going back and tweaking these simple tasks!
Where to Find This Info:
So, where do we find these mounting heights and any special rules pertaining to our building?
The site specs are that particular job site’s guidelines on how the engineer wants the job done. (Don’t let those slip through the cracks. It’s really important stuff – it can be the difference between a pass and fail through your inspection/walkthroughs.)
Plywood Floors in Condos – Poured Concrete Adds 1.5″:
Another super important tip about mounting heights in condos is when you are on a plywood floor.
For example, your first floor is the actual concrete slab, so your mounting heights are exactly as they are told to you on the site specs.
But, once you go up a floor in a wood framed condo, you are then walking on a plywood floor which eventually gets poured with 1.5″ liquid concrete! (If you don’t take this into account, all your devices will be 1.5″ too low!)
How this works is the framers install two bottom plates on the floors above the main concrete slab.
When they pour the liquid concrete (called gyp-crete), they pour it just enough to cover the first 2×4, which is 1.5″.
So on the floors above the main concrete slab which are just plywood during your rough-in stage, you have to add 1.5 inches onto the given measurements, as the prints typically say A.F.F. which stands for Above Finished Floor.
The plywood floor is not your finished floor, the poured concrete is!
Not adding 1.5″ to your mounting heights before concrete is poured on your upper floors is a rookie mistake to make!
ALWAYS CONSIDER DRYWALL DEPTH (BEING IN IS BETTER THAN OUT)
The next thing you want to consider is your drywall depth.
Especially when working in condos, we can deal with 1/2″, 5/8″, or multiple layers of drywall. (Sometimes soundbar is also included which adds even more depth.)
What this means is you have to break off the tabs on your box so you can stick the box out to the correct depth.
Now, in my experience, it’s ALWAYS BETTER TO BE TOO FAR IN than too far out.
There is a code rule that specifies how far you’re allowed to be in the drywall, but you can easily use a box extender so you can comply with these rules.
When a box is too far out you have to cut down the plastic to make it flush with the drywall. Otherwise, when you install your device, your cover plate will have a noticeable gap in it! (This is a horrible fix to have to make.)
So where do you find this information on drywall depth?
You’d find drywall depth info on the architectural prints.
There’s usually a page which shows you all the different types of walls/ceilings and what each wall/ceiling gets. It tells you exactly from start to finish that exact materials used.
For example, let’s say our wall designation is P2:
- Finished Paint Color
- 1 Layer 5/8″ (Suite Side)
- 2×6 Roxull Insulation
- 2 Layers 5/8″ Drywall (Corridor/Hallway)
- Finished Paint Color
So wherever you’d see the P2 designation, you’d know what side gets 2 layers of 5/8″ drywall and what side only gets 1 layer.
It’s tricky to keep track of drywall depths, so sometimes you can use spray paint studs to determine drywall depth ahead of time, or just simply write on the stud to save yourself from always checking.
Don’t forget about your ceiling drywall depth, too. Especially in a condo, these drywall depths can change, like if you were on the top floor compared to the first floor for example.
DOES THE LAYOUT MAKE SENSE?
This one will happen with experience, but over your years you’ll pick up the common tricks for laying out boxes and if the layout has an error or is kind of funky feeling.
- Are the plugs all within 12′ and on usable wall space?
- Do the 3-way switches make sense?
- Do the prints show the panel in a closet? (Not allowed!)
RECOMMENDED BOXING TIPS FOR AN AWESOME WORKFLOW
So if you’re ever in charge of apprentices or left alone, here’s my recommended tips to you when you’re on a brand-new job site and now it’s time to start boxing!
- Find your mounting heights first – I’d also suggest to cut templates out of wood. For example, cut a piece of wood at your switch height and a piece of wood for your plug height to save time. If your boss doesn’t like that then I guess you’re going to have to use a tape measure. Make sure to cut new template sticks when you move up to floors that require you to add 1.5″ because the concrete is not poured yet, or you’re devices will all be 1.5″ too low!)
- Walk around the rooms with prints and draw symbols on the studs where devices go and mark the heights, too!
- Layout all your boxes underneath the studs, making sure the outside boxes are vapor barrier boxes.
- Cut and layout scabs for boxes where they should be out 1 or two stud spaces. (To get away from the door frame trim, if a box is three gang or larger, or if it’s too close to another box, for example.)
- Load up on 1″ screws for your boxes and long screws for your scabs (Sometimes a company will use nails instead of long screws for scabs. Nails are less expensive, but screws are definitely faster.)
- Grab your drill and have at it!
This is by far the fastest way I’ve found to box out a suite in a condo or home.
Hope your boxing improves 😉