Outdoor wiring

[Downaski]

Hi everyone!

When running outdoor wiring for a deck, is it better to use direct burial cable (UF) or conduit with THWN wires? What are the pros and cons of each approach in terms of durability, maintenance, and ease of installation?

[TinyTool]

Hi!

If you’re deciding between direct burial cable (UF) and conduit with THWN wires for your outdoor deck wiring, there are a few things to think about. Direct burial cable is quick and easy to install since it’s designed to be buried without needing extra protection. It’s tough enough for outdoor use but, if it gets damaged, fixing it can be a hassle because you’d need to dig it up to replace it.

Conduit with THWN wires, on the other hand, provides better protection. The conduit shields the wires from physical damage, and if something goes wrong, it’s easier to replace the wires because you don’t need to dig everything up. However, it takes more time and effort to install, and can be a bit pricier because of the extra materials and work involved.

If you want something quick and cost-effective, UF cable is a good choice, but if you’re looking for something more durable and easier to work with down the line, conduit might be worth the extra effort.

[Downaski]

Thanks for the explanation. Could you kindly confirm if conduit requires a deeper burial depth compared to UF cable?

[TinyTool]

Generally, conduit does require a deeper burial depth compared to UF cable. For UF cable, you’re usually looking at a minimum of 24 inches if it’s directly buried. On the other hand, conduit (like PVC or metal) often has a shallower depth requirement, typically around 18 inches, since the conduit adds extra protection to the wires inside. That being said, local codes might vary, so it’s always a good idea to check with your local building department just to be sure!

[Downaski]

Thanks for the info! Just to clarify, would the type of conduit (PVC vs. metal) affect the burial depth requirements?

[TinyTool]

The type of conduit you use, whether PVC or metal, does impact the required burial depth for electrical wiring. PVC conduit, like Schedule 40 or 80, typically needs to be buried at least 18 inches below the surface, although Schedule 80 is required in areas prone to physical damage, such as near driveways. On the other hand, rigid or intermediate metal conduit, which offers greater protection, can be buried much shallower, at just 6 inches. If you're running direct burial cable without any conduit, the depth requirement increases to 24 inches. However, special situations like wiring under concrete slabs may allow for a depth as shallow as 4 inches, and circuits protected by GFCI breakers might reduce the burial depth to 12 inches in some cases. It's always a good idea to double-check with your local building codes to ensure compliance with specific regulations in your area.

[Downaski]

Would Schedule 40 PVC conduit work for running wiring under a garden path, or should I use something more robust?

[TinyTool]

Schedule 40 PVC conduit should work just fine for running wiring under a garden path. It’s sturdy, won’t rust, and can handle outdoor conditions well. Just make sure to bury it deep enough—around 18 inches is usually good—to avoid any damage. If the path sees a lot of heavy traffic or you’re worried about extra wear and tear, you could go with Schedule 80 PVC since it’s thicker and tougher. And don’t forget to seal the ends to keep water out, especially if it’s a rainy area. For anything heavier, like cars or machinery crossing, you might need to step up to metal conduit, but for most garden paths, PVC does the job!

[Downaski]

Thanks so much for the detailed advice Tinytool!