how deep should PVC conduit be in slab?

skinut2234

OK in preparation for the kitchen island - I'm cutting a channel into the slab to run electric (about 2' from the wall)- I cut down about 2.5" and about 3.5" wide in the concrete - I rented a power chisel. To go deeper seems to really be a challenge- Can I lay the PVC in and cover with concrete from here? What determines the depth that it needs to be? I can't see weight being an issue- Once the concrete hardens around the PVC and the floor gets installed.....thoughts? suggestions?

jrclen

The National Electric Code determines this. Table 300.5 note 2 requires the conduit to be surrounded by 2" of concrete. What size conduit are you using?

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John

skinut2234

3/4" PVC Conduit

electures

The NEC does not require the conduit to be surrounded by 2" of concrete. It can be laid on the soil and concreted over.

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Gac66610

It needs to be covered by 2" of concrete

mpoulton

The standard approach to solving this problem is to cut all the way through the slab with a saw, and lay the conduit under the slab. It is easier than making a shallower channel. Chiseling a channel through concrete is REALLY HARD as you discovered, but making two sawcuts through the slab a few inches apart is really easy. You still need a rotohammer or small jackhammer to break up and remove the pieces, but it's about a 30 minute job with the right tools, rather than all day with a rotohammer trying to chisel 3" deep groove in the slab.

electures

No. Since it is under the building it can be 0" deep. It is covered by the thickness of the slab.

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Jim Port

Could you cite the NEC rule for this?

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Gac66610

Table 300.5, Notes

electures

If you are refering to Note 2, it states;

PVC does not require concrete encasement and is "Listed for direct burial without concrete encasement", therefore Note 2 does not apply. Refering to Table 300.5, Row 3, labeled "Under a building", Column 3, the required depth is 0". The OP just needs to break through the slab and lay the PVC on top of the dirt. Then concrete over the pipe. Done.

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Code05

300.5, Note 2 is referring to conduit like EB20 - not PVC 40 or 80.

skinut2234

let me clarify- I don't know how thick the slab is- It's not a new house- it's an existing house built in the mid 70's in NJ. I was going with the channel since after chiseling down 2" or so- It's getting really hard to go any deeper and I thought by going down 2" and then laying the PVC in the slab- I could cover it back up with high strength concrete. Won't that keep the PVC well secured?

jrclen

Can you cite something on this? I really would like to know. I have laid PVC in concrete channels cut in slabs and was required to cover the conduit with 2" of concrete. Evidently some slabs are not allowed to be cut through. But that's completely out of my field so I may well be wrong about this.

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herdfan

That would be tensioned concrete. They have steel cables running through them keeping tension on the concrete. If one gets cut, the concrete can lose some of its strength.

Gac66610

So you (a long with others) are saying that PVC can not be used in concrete?
I read Notes 2, and 5, both say minimum of 2" concrete, so how would a slab be any different?