UG Conduit on Ground Level of Parking Structure

[Dustin Foelber]

We are installing underground conduits on the ground level of a parking structure and we are a bit unsure on what minimum depth applies.
Essentially we are under concrete of an interior building structure in which the 4" limit would apply. But this area is exposed to vehicular traffic, so we are unsure if the 24" limit applies.
Any input would be greatly appreciated.
Thank you

 

[petersonra]

interesting question.

 

[charlie b]

The 4" depth would not apply because you are not talking about an exterior slab. The 24" depth would not apply because you are not talking about a roadway. My answer is there is no minimum depth (in other words, 0" depth is acceptable), because you are under a building. I realize the weight of cars could be a matter of concern. But keep in mind there is also the entire weight of the building already being imposed on the building's support structure. The additional weight of a car is nothing in comparison. The entire third row in table 300.5 says 0" for under a building, regardless of the wiring method. So the code's authors are not concerned about any weight of any component of the building or its contents damaging the wiring method.

 

[Smart $]

... The 24" depth would not apply because you are not talking about a roadway. ...

The last item of the 24" requirement is "parking lots". I believe the AHJ will see it as such.

The contradictory part is, for any level above grade, you could embed in the concrete slab work and it would be compliant because it is not underground.

 

[petersonra]

The last item of the 24" requirement is "parking lots". I believe the AHJ will see it as such.

The contradictory part is, for any level above grade, you could embed in the concrete slab work and it would be compliant because it is not underground.

I don't believe this is a parking "lot". I don't see anyone who has spent time with the code seeing it that way either. It just is not a parking lot, otherwise the term "parking lot" as used within the code would have some serious issues.

Having said that, if you can get someone to pay you to bury the conduit under the building, it would not bother me one bit if you did so.

 

[rambojoe]

beware.... the city might require 4 to 5' of concrete on driveways that lead to the street. that means the concrete guys will hit your pipes if they happen to be run through there. just a courtesy.... should be on the concrete details/civils or whatever. of course that's if pipes are pre installed. and we know how nice the rebar guys are to our pipes. if it can go deeper and you have the equipment its sure safer deeper imo.

 

[Dustin Foelber]

Thank you,
Sounds like this one is going to have to go to AHJ for clarification. Has anyone out there dealt with this application before??

 

[Mr.Man]

But What if?

But What if?

What if a 1" rigid steel conduit is installed under a parking lot (gravel)? Perhaps in a 6" trench. Does it have to be 24" deep since it is beneath a parking lot, or can it be 6" deep with a 2" concrete slab on top?

 

[Dennis Alwon]

What if a 1" rigid steel conduit is installed under a parking lot (gravel)? Perhaps in a 6" trench. Does it have to be 24" deep since it is beneath a parking lot, or can it be 6" deep with a 2" concrete slab on top?

As I read 300.5 it needs to be 24" deep.