Underground versus encased in concrete foundation

[FaradayFF]

I'm running several conduits from a building to an enclosure that will be constructed concurrently with the conduit install. The rebar reinforced concrete foundation of this enclosure is about 2' thick.

Would I be better off having the contractor place the conduits under the slab or are there any advantages of having the conduits embedded in the concrete?

I'm thinking of using GRC.

Thoughts?

Thanks,
EE

 

[LarryFine]

Wouldn't the grade and burial depth be the deciding factors?

 

[FaradayFF]

Hi Larry,

Can you elaborate please? It is a relatively short run with one row of conduits being installed, so I don't see any advantages one way or another..

Thanks,
EE

 

[Buck Parrish]

You'll be better off to go under the slab .Unless it's small conduit.

 

[FaradayFF]

Wouldn't this approach be creating an extra step during the construction? The contractor would be placing the conduits, backfilling and then pouring the concrete on top..I think the backfilling part concerns me abit, but it shouldn't be a lot of effort here.

Thanks,
EE

 

[Buck Parrish]

Yes it's an extra step. But that's what we do. While the GC is locating walls, etc...that would be a good time. Generally when the slab is close to finish being graded . Before the gravel goes in. It depends on the size of the conduits.

 

[LarryFine]

Hi Larry,

Can you elaborate please? It is a relatively short run with one row of conduits being installed, so I don't see any advantages one way or another..

Thanks,
EE

Picture the installation from the side, like a cutaway drawing. As the conduit running underground approaches the building, and is, let's say, 18" deep, it will also be below any slab at grade level. The only way to run the conduit into the edge of a slab would be if the slab is also about 18" below grade.

In other words, if the slab is shallower than the conduit, the conduit will by default be below the slab, and you'd have to intentionally offset the conduit vertically to get it into the slab. If the slab is deeper than the conduit, the conduit will penetrate the "basement" wall, and will already be above the floor.

 

[infinity]

I would just run it in the slab. I see no advantage to burying it especially if it's RMC.

 

[synchro]

Is there an isolation joint between the slab and the wall or footing? If so then the joint is there to accommodate possible movement, and then having conduits span across the joint might create strain and possible localized slab cracking in the future if there's any settling. If the slab is contiguous with the wall or footing with no gap between them, then there should be no issue putting the conduits in the slab.