Does Romex Need Conduit? (Here’s How To Install It!)


Romex is one of the most popular brands of non-metallic sheathed cable. Today, this name is used to refer to most cables of this type, regardless of their brand. 

Non-metallic (NM) sheathed cable is used in a variety of residential applications. It generally runs through walls, ceilings, or attics. Exposed installation is also possible, but in this case, the cable might need protection.

However, many people are confused as to whether they have to run Romex through conduits. 

According to the code, Romex must be protected from physical damage whenever it is used in exposed installations. However, it doesn’t need conduit specifically. You can also protect it with covering boards or guard strips. When it runs through walls, ceilings, or attics that provide thermal insulation, Romex can be installed as it is.

When Does Romex Need Conduit? 

Romex doesn’t necessarily need conduit – it all depends on where you need to install it. 

Generally, the code says that non-metallic sheathed cables should run concealed within walls, ceilings, and floors that can provide thermal protection. In other words, it’s perfectly fine to run Romex through the wall or attic insulation. 

That’s because the sheathing is generally made from materials that are fire-retardant but could be damaged by temperature fluctuations. 

However, the code also allows the use of Romex in exposed installations. In this case, you must protect the cable from physical damage. 

Running Romex In Exposed Locations 

When installing Romex in exposed locations – either inside your home or in a garage, basement, or attic – you must comply with certain regulations.

The code might vary based on your location, but generally: 

  • You must install the cable flush with the wall or running boards.
  • Protect the cable with rigid metal conduit or another approved conduit type when running it through the floor. 
  • Use guard strips when running the cable exposed through attics or for ceiling installations. 
  • You must protect Romex with conduit or tubing when installing it on the walls of an unfinished basement. All metal elements, including metal conduit or tubing and metal outlet boxes, must be connected to a grounding conductor. 

In addition to using conduit or other types of tubing, you must also secure Romex properly to the surfaces.

As a general rule, you should fasten the cable in place within 12 inches of each cable entry, including entries into fittings, junction boxes, cabinets, or outlet boxes. All other straps or staples should be set at intervals of maximum 4½ feet. 

Does Romex Need Conduit When Installed On Concrete? 

As explained above, Romex needs conduit when it is installed in any exposed location. This means that you might have to use conduit if you want to run the cable along a concrete wall in an unfinished basement. 

However, you don’t have to use conduit or other tubing if you’re running the cables through the walls.

Things are different if you’re running the cable through the floor. In this case, you have to use rigid conduit or another type of approved conduit – check with your local building department to know what tubing to use.

Does Romex Need Conduit When Running Through Ceiling Joists?

No, you generally don’t have to use conduit when running Romex through ceiling joists. This is a concealed type of installation, and you can install the cable as it is. 

However, you might have to use guard strips or covering boards if you’re installing Romex in an attic. 

Guard strips are required for all attic installations. In accessible attics, the entire length of Romex running through the cavity must be protected by guard strips if it is installed on the floor.

Otherwise, guard strips are necessary for the first seven feet from the attic entrance. 

In inaccessible attics, you must protect the first six feet of cable from the attic entrance with guard strips. The rest of the cable doesn’t need protection from damage, but you must secure it properly and run it flush against the surface to prevent sagging. 

Can You Run Romex Outside Without Conduit? 

You can’t run Romex outside, with or without conduit. Romex is a type of non-metallic sheathed electrical conductor, and this cable type is not approved for outdoor use. 

Where Can You Use Romex? 

Romex is approved for indoor installation in most residential buildings and garages. You cannot use it outdoors, even if buried underground.

That’s because the thin sheath provides minimal protection from temperature fluctuations, and it can tear off easily. 

Generally, you can use Romex in single or multi-family dwellings that are one or two stories tall. However, it can only run exposed through dropped or suspended ceilings in one- or two-family homes.

The code also prohibits the use of Romex as service-entrance cable. 

What Cable Can You Use Outdoors? 

Running Romex outside a dwelling is against the law, but what cables can you use to run electricity to your home? 

According to NEC, you can use direct burial (UF) cable for outdoor applications. UF cable is the most common cable type for outdoor residential wiring. This cable must be installed underground, without conduit, in trenches that are at least 24 inches deep.  

If you can’t bury it in trenches that deep, you can still use UF cable but protect it with rigid metal or intermediate metal conduit. In this case, trenches can be only six inches deep.

With PVC conduit, you can install it in trenches that are at least 18 inches deep.

Can I Use PVC Conduit With Romex? 

There is a lot of debate as to whether Romex needs conduit and – more specifically – whether you can use a PVC conduit when installed in exposed locations. 

Some people vehemently recommend avoiding PVC because the material allegedly traps heat and could damage the cable. 

However, this is not true. According to the code, where the cable can be damaged physically, it must be installed in conduit.

Approved conduit types include Schedule 80 PVC, rigid and intermediate metal conduit, RTRC-XW, and other equivalent conduit types.

To End 

Romex doesn’t need conduit for most residential applications. However, you must install it through conduit whenever the cable is exposed or could be subject to physical damage. Failure to do so could mean your home wouldn’t pass an inspection, and you also increase the risk of short circuits and electrical fires.

Roxana Bikfalvi

Roxana is a copywriter passionate about home improvement and interior design. When she’s not writing, you can find her upcycling old furniture or remodeling interiors. She has written for numerous home improvement blogs before joining PlumbJoe.

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