Can Romex Be Stapled To The Bottom Of Floor Joists?

When it comes to wiring ceilings joists or floor joists, you need to consider a large number of considerations before you finalize what method you will adopt. You can find these joists by going up into the attic or simply by making your way into the crawl space underneath.

It’s one thing to consider whether or not you can run Romex in these crawl spaces, it’s entirely another to consider how you will run the wire. DIY-ers often ask if Romex can be stapled to the bottom of floor joists or not and other liberties they can take.

It is okay to staple Romex along the floor joists, provided you keep it at a safe distance from the edge. This will help you protect it from screws and nails and any critters that may be crawling along the edges – since that is where insects usually decide to burrow. You can also run Romex THORUGH floor joists. However, there are some considerations to make that we will discuss in this article.

Can Romex Be Stapled to the Bottom of Floor Joists?

Can Romex be Stapled to the Bottom of Floor Joists?
Random arrangement of metal staples still joined together in rows

Whether you are taking down your ceiling to run some electrical wire or simply looking to run some new wire to new outlets, you may find yourself having to face the predicament of having to staple Romex to the bottom of the floor joist.

If you have an unfinished ceiling, we would recommend going through the joints when going perpendicular to get to the final destination. However, when you are taking the same wire to the breaker, you can either use a conduit or simply staple the wire directly.

It isn’t uncommon in the US to see some bent nails acting as homemade staples to secure the Romex or other wire passing along the floor. Even builders do this when they are working on an unfinished ceiling so that they can replace it with staples later on.

As mentioned above, this practice is completely fine, so long as the crooked nails are replaced with staples at the end. With the help of staples, the wire can be nailed across straight paths for quite a distance before it becomes a hazard. Remember, though, that the screws, nails, or the staples holding the wire should be evenly spaced in such a manner that the wire isn’t sagging from anywhere.

On the other hand, it is against NEC and building code to staple Romex in a “cross beam” fashion, i.e., running the wire from beam to beam, no matter how tightly the wire is stretched. This is because the wire doesn’t have anything on its back, which is ultimately classified as a ‘hanging’ wire.

If you want to do this, you will need to drill holes and run the wire through the beam and fasten it properly. An insulated Romex staple will be better here and if possible, brace it as much as possible. If you are short on material, position a brace mid-way between beams.

This will be a bit labor intensive but the alternative is to run the wire all the way around these joists, which will take up more material. The goal is to prevent animals (and people) to hang things from the wire in both finished and unfinished ceilings.

Here is an excerpt from the NEC Code, Chapter 3: Wiring Methods & Materials.

Chapter 3 Wiring Methods and Materials

Article 334 Nonmetallic-Sheathed Cable: Types NM, NMC, and NMS

II. Installation

334.15 Exposed Work.

(C) In Unfinished Basements and Crawl Spaces. Where cable is run at angles with joists in unfinished basements and crawl spaces, it shall be permissible to secure cables not smaller than two 6 AWG or three 8 AWG conductors directly to the lower edges of the joists. Smaller cables shall be run either through bored holes in joists or on running boards. Nonmetallic-sheathed cable installed on the wall of an unfinished basement shall be permitted to be installed in a listed conduit or tubing or shall be protected in accordance with 300.4.

Conduit or tubing shall be provided with a suitable insulating bushing or adapter at the point the cable enters the raceway. The sheath of the nonmetallic-sheathed cable shall extend through the conduit or tubing and into the outlet or device box not less than 6 mm (¼ in.). The cable shall be secured within 300 mm (12 in.) of the point where the cable enters the conduit or tubing. Metal conduit, tubing, and metal outlet boxes shall be connected to an equipment grounding conductor complying with the provisions of 250.86 and 250.148.

NEC Code, Chapter 3

The code suggests that a conduit should be used when passing wires or “conductors” underneath the bottom of floor joists – yet, it doesn’t say that stapling is prohibited, either. Instead, it says that “the cable shall be secured within 12 inches” – and that’s about it.

Stapling Romex – Height From The Bottom

Romex wire which is stripped at one end
Romex wire which is stripped at one end

When running a wire underneath the floor joists you will need cables no more than 6 gauge. Anything more and you will have to make other arrangements. When running between joists, it is best to use running boards that run between floor joists. Code doesn’t specify any height requirements because electricians all over the globe believe that the height can be variable with respect to where we live.

For example, in damp areas, the height needs to be more while in drier areas, this height can be slightly less. According to code, Romex should be stapled at intervals of at least 4.5 feet. More frequent staples are more than welcome but anything more and the cable will start sagging.

The last (or first) staple before (or after) a breaker or a junction box should be no more than 12 inches away according to code.

It is important to point out here that stapling the wire perpendicular to the joists is not a very acceptable way of installing the Romex NM cable. The best way is, in fact, by using a conduit. This isn’t just a code recommendation but something that all electricians agree to be the better solution – albeit a bit more expensive than simply stapling everything.

Installing Romex Wires To The Bottom of Floor Joists

When looking to install Romex wires to the bottom of floor joists, we would recommend cutting pieces of cheap 2×4’s and installing the same between the joists for each joist. You should consider nailing or screwing the pieces flat on top of the wire.

Remember, you don’t have to go all-in for the 2×4’s. Even scrap wood and nails (or screws) should be enough to get the job done. With the help of these screws and nails, you will not only be code compliant but you will also be making your floor or ceiling stronger in the process. Again, this is a slightly more time-consuming task, but you get to save up on costs, meet code, wire your house, and improve the integrity of your house in the process.

You can staple the wire on top of this wood either with the help of a staple gun, hammer some nails and bend them, or even use screws to fasten the wire to the wood. So, in essence, Romex can be stapled to the bottom of floor joints without any issues.