Whether you are wiring in your basement, crawl space, attic, garage, or even in your kitchen, you might have to pass several wires from the same point before splitting them up. This could either be for aesthetics or to ensure functionality.
A common question people ask when two or more wires need to be passed from the same point is whether or not you can stack Romex under one staple. This question is frequently asked by DIY-ers and for good reason.
In most cases, stacking up to 3 Romex cables under one staple is allowed. However, certain conditions need to be met. There are no specific requirements under code for the staple being used. However, DIY-ers need to keep in mind that metal staples aren’t just cheaper, but they are also much better than plastic ones (albeit not as pretty).
Can You Stack Romex Under One Staple?
The reason for this question may arise in the first place is that when you staple wires, they get compressed. Over time, if the staple is too tight, it can start eating up the insulation or rubber underneath it, effectively exposing the conductors in between and getting energized. The weak insulation presents a risk of electric shock and conductors shorting out.
Hence, if you choose to staple more wires, i.e., stack them under one staple, there is a good chance that with time, especially in humid places where the metal will rust up, the wires may end up touching one another or the staple itself.
An obvious solution to this would seem to be plastic ones. Not only are they better looking, but they also don’t erode. However, this isn’t a sustainable solution since plastic staples are supported by nails on one or both sides. The nail will need to be hammered into the wall. This makes it much stronger and firmer in place, but the same cannot be said about the grip it has on the wire.
There are different plastic “staples” or braces for different wire sizes. When used for the dedicated wire size, these braces perform much better than metal staples. However, to brace two or more wires, you will need to buy braces fit for a bigger wire – not those suitable for several wires. The wires will end up crushing each other, effectively being more harmful at the end of the day.
Another issue with plastic staples on Romex is that they can be relatively hard to install in hard-to-reach places. We prefer metal ones, especially if we aren’t using conduits. However, if you are using those PVC channels, you would be better off using these plastic braces.
Things to Keep In Mind When Stacking Multiple Romex Wires Under One Staple
When stacking multiple Romex wires under one staple, the general rule of thumb is to always wire just one wire per stable, and if you really must, staple no more than two wires side by side. In the field, anything more than two wires at a time is known as a stack.
Most metal and plastic staples or ‘wire holders’ can hold stacks of up to six to eight (6 to 8) Romex wires under them. You can stack even more if you can fit them or use thinner wires.
However, it is not permitted by code to stack more than one 3-conductor cable under a staple, be it metal or plastic. If you must stack, you should consider doing it only if you plan on using single or double conductor wires. If you need to pass several wires from the same spot, we recommend using stacker-type fasteners. These fasteners can hold on to up to three wires easily, but again, we recommend you don’t run more than three wires through a single cable.
Since the goal is to stack the wires in a much neater and safer way, these fasteners can be the perfect solution.
What Does The Code Say About Stapling Multiple Wires Under One Staple?
Now that we know what professionals prefer and what they do, consider what the NEC Code recommends. As per Code section 310.15(B)(3)(a),
Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(3)(a). Each current-carrying conductor of a paralleled set of conductors shall be counted as a current-carrying conductor.NEC Code 310.15(B)(3)(a)
This statement is slightly unclear in terms of its representation and, therefore, houses several arguments from time to time. According to the first line, if you are stacking three or less than three cables under a single staple, you are good to go. However, if there are four, you are violating the NEC code.
Another translation is that this statement refers to the conductors within a wire. Romex typically has three conductions within it, and it means that Romex can’t be stacked at all.
According to NEC, the goal of this provision is to keep the heat within a conduit or a stack down to a minimum and, therefore, avoid a meltdown.
However, there is something that may save you in an inspection even if you have stacked the wires, and it’s using modern nonmetallic wires made from THHN. These wires are usually rated for 90 degrees centigrade, which means that they can take on heavy loads pretty easily. This is particularly true if you are starting with 30 amperes.
We prefer installing just one Romex under each staple – and this is not just us. Professionals all over the globe do it the same way. The only difference is that in the US, there is a very limited concept of plastic staples, and there is a risk of crushing the cable or tearing it. This is a very serious consideration to make.
Does Romex Even Need to Be Stapled?
Leaving Romex wires exposed, i.e. unstapled or hanging loose, is a direct code violation, especially for new construction homes. Regardless of whether you are remodeling a wall or a contractor has just finished a new construction home, you need to remember that the wires should be anchored to the wall separately if possible.
If stacking Romex cables is important, it must be done with stack fasteners and not under staples to make sure that there is no risk of your house failing inspection, and therefore, you get fined.
The clamps, staples, or braces holding a Romex cable shouldn’t be any further than 4.5 feet. However, we recommend stapling after every 2 feet, just to be sure. This is especially true when running a wire where you won’t have immediate access all the time. The first and the final staple, on the other hand, should be no further than 12 inches from the junction box, breaker box, or the wire’s final destination.
Another important factor to considering when you want to stack Romex under one staple is what your inspector prefers. It is a good idea to ask them before you start working. For example, in South Dakota and Minnesota, there have been many instances where people have complained that inspectors are strict about having no more than just one Romex under a staple while the same allows for 3 cables under a staple when tested in other states such as New York.