Separate structure?

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Greentagger

Greentagger

Senior Member
Location
Texas
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Master Electrician, Electrical Inspector
Would a separate building on the same concrete slab have to comply with 225.31& 225.32? Specific situation is the service for the residence has been built on the garage. The garage and house are not connected structurally other than the slab. The service at the garage is an exterior service panel board with a main breaker. From there an overcurrent protection device is used to feed a panel back to back to serve garage. Also is an overcurrent protection device which feeds the main residence MLO panel by way of an underground feeder. Is a disconnecting means required “at“ the main residence? Opinions and interpretations welcomed. Thanks.
 
225.31 requires a disconnecting means for all ungrounded conductors that supply the structure and 225.32 requires that disconnecting means to be inside or outside of the building served.
Are you thinking the disconnect at the garage is allowed to be the disconnect for the main residence?
 
kwired said:
If common slab makes it the same building then there are many mega buildings out there connected by driveways, streets, etc.
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I see where you’re going, but I think a single slab with common rebar running through it might be different? Interesting debate!
 
tom baker said:
225.31 requires a disconnecting means for all ungrounded conductors that supply the structure and 225.32 requires that disconnecting means to be inside or outside of the building served.
Are you thinking the disconnect at the garage is allowed to be the disconnect for the main residence?
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No. Initially I thought it needed one. But heard another opinion and was willing to let them plead their case. Which as the snowball grows , if it requires a disconnecting means at the main residence now it appears 250.32(A) may be necessary? Thanks.
 
retirede said:
I see where you’re going, but I think a single slab with common rebar running through it might be different? Interesting debate!
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Most the time when one slab buts against another they stub rebar out from one into the other. If butting up to an existing slab they drill holes in existing and insert rebar in those holes to tie the two together. Not quite the same thing as if it were poured, though they could epoxy them in and get even closer to that kind of thing. Mostly they just want them to keep from having vertical differences after finished. Poor compaction below one or the other slab will eventually cause a failure down the road anyway.
 
JMNSHO.

I don't think it matters if there is common rebar or not. If it is on the same slab, it is a single structure.

If concrete has been poured between two separate slabs, it probably is not a single structure, unless some means of tying the slabs together has been used. Then it is likely a single structure.

OTOH, it also may depend on what you are calling a "slab". IMO, a concrete floor does not count as a "slab". It's only a "slab" if the structure is supported by it. I also do not think a sidewalk or driveway poured between two foundations counts as a slab, regardless of whether it is tied into the foundations.
 
petersonra said:
JMNSHO.

I don't think it matters if there is common rebar or not. If it is on the same slab, it is a single structure.

If concrete has been poured between two separate slabs, it probably is not a single structure, unless some means of tying the slabs together has been used. Then it is likely a single structure.

OTOH, it also may depend on what you are calling a "slab". IMO, a concrete floor does not count as a "slab". It's only a "slab" if the structure is supported by it. I also do not think a sidewalk or driveway poured between two foundations counts as a slab, regardless of whether it is tied into the foundations.
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NEC does not define this term. From whatever dictionary google came up with first hit came up with pretty generic definition : a large, thick, flat piece of stone, concrete, or wood, typically rectangular.
 
“Slab” seems to be the sticking point.
What if they shared a “contiguous foundation”. I know, that’s not defined, either. But I would think they could be treated as a single structure if they are built on the same foundation. It’s basically just another room - with a bit of outdoor space (breezeway?) in the middle.
 
IMHO this must be a subjective call. Would a reasonable person who needs to shut off power to the building recognize the disconnect on the garage as being the building disconnect. Is the disconnect on the garage in close proximity? (Again close is subjective. )

Consider a building with meter and main disconnect mounted on a strut frame 6 feet away from the building itself. That would certainly be recognized as where to go to pull the switch. But something down at the other end of the driveway even if connected by a contiguous slab? Not so much.

If it is subjectively clear that the disconnect is part of the same overall structure then it _is_ part of the same structure.

Jon
 
OP mentions that the feeder from the garage service goes underground to the house. If it goes through this potentially unifying slab, would that make any difference? IMO, it would at least add to the argument that the two buildings are intertwined with one another enough to not require a second disconnect.
 
I don't think it matters one iota whether a "reasonable" person would be able to tell anything from a quick glance. The code just does not use that kind of language.

Either it is one structure or it's not. The electrical code does not define this but I'd be willing to bet that somewhere in some building code it is defined.
 
petersonra said:
I don't think it matters one iota whether a "reasonable" person would be able to tell anything from a quick glance. The code just does not use that kind of language.

Either it is one structure or it's not. The electrical code does not define this but I'd be willing to bet that somewhere in some building code it is defined.
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Does NEC reference other building codes for such a thing? I know they to give references in informational notes here and there, but those are just that, informational and not a requirement.
 
Our inspector over here said they make the distinction for attached/detached based on whether the roof systems come together. Seems reasonable to me.

A slab would be a nonstarter, like the others mentioned.
 
kwired said:
Does NEC reference other building codes for such a thing? I know they to give references in informational notes here and there, but those are just that, informational and not a requirement.
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As best I can tell the NEC does not define the term "separate structure" even though it is used several times.

There are plenty of terms the NEC does not define that are defined in other standards.
 
petersonra said:
As best I can tell the NEC does not define the term "separate structure" even though it is used several times.

There are plenty of terms the NEC does not define that are defined in other standards.
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art100scope.JPG

Doesn't really state what definition applies if not in art 100 or in the article it happens to apply to either. That is pretty much left to interpretation of the user or AHJ. A definition in another building code that applies to the application is a start, but is not enforceable as being NEC requirement either.
 
kwired said:
A definition in another building code that applies to the application is a start, but is not enforceable as being NEC requirement either.
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No, but it is enforceable as a building code requirement. Just because one is an electrician does not mean one is exempt from following any building code other than the NEC. HVAC guys have to follow the NEC with respect to electrical installation issues even though they are not electricians.
 
Lots of good input. I too immediately looked up to see if the roofs were joined. They were in close proximity but not together.
 
petersonra said:
Either it is one structure or it's not. The electrical code does not define this but I'd be willing to bet that somewhere in some building code it is defined.
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I think as far as the electrical code is concerned, a 'structure' is 'I know it when I see it'.

However you have a very good point here. Even if the electrical code does not define what a single structure is, and even if other codes are not explicitly referenced, the 'structure' as defined by other building codes would be a great place to discover a solid definition.

I like the 'connected roof' metric for deciding if the house and garage are a single structure for purpose of interpreting the NEC, but I am pretty sure that this is Cow's inspector's interpretation of local codes.

-Jon
 
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