Wires perpendicular to joists in basement

We can’t run wires perpendicular on bottom of joists in basements (or crawl spaces) unless it is #6 or bigger. This is what the inspectors have been telling us. But what if there is a suspended ceiling? Is it ok then ?
 

kwired

Electron manager
Location
NE Nebraska
Good question.

New construction I always do the initial rough in drilled in. Additional wiring between lights after the ceiling is hung is usually attached to bottom of joists though when it runs perpendicular to the joist.
 

kwired

Electron manager
Location
NE Nebraska
The restriction is for unfinished basements. If there is a finished room with a hung ceiling there is no restriction on running on the underside of the joists.
They did add crawlspaces in one of the more recent NEC editions. (recent meaning maybe up to 15 years ago, time flies...)
 

James L

Senior Member
Location
Kansas Cty, Mo, USA
Occupation
Electrician
It is absolutely acceptable to run perpendicular to the joists - UNDER joists - in a grid ceiling

334.12(a)2 permits it "within" grid ceilings

335.15(c) states that in UNFINISHED basements it cannot be under joists if smaller than #6

That prohibition for unfinished basements doesn't apply to a finished grid ceiling
 

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infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I disagree. 334-15 Exposed work install per A-C
definition of exposed Art100
can you run NM perp to joists if exposed?
Not unless it's 6-2 or 8-3 or larger. The OP is asking about running under the joists above a drop ceiling which is permitted for any size NM cable.
 

kwired

Electron manager
Location
NE Nebraska
Like when people say "under counter lights"

I be like....under the counter would be the lower cabinet 😁
I hear that a lot as well.

As far as I'm concerned as long as we are within a strong influence of Earth's gravitational effects, down, under, below, etc. is the direction of pull of Earth's gravity on all the smaller objects. Even if you are standing on your head.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
One of those situations where one has to be careful what is said.
I have had inspections where the NM is on the bottom of the joists in an unfinished basement and I have mistakenly said "if it had a drop ceiling it would have been ok"... only to return to find a suspended ceiling in rooms that had no wall receptacles whatsoever,... now what do we have ?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
One of those situations where one has to be careful what is said.
I have had inspections where the NM is on the bottom of the joists in an unfinished basement and I have mistakenly said "if it had a drop ceiling it would have been ok"... only to return to find a suspended ceiling in rooms that had no wall receptacles whatsoever,... now what do we have ?
"Well, I didn't say 'only'!"
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
One of those situations where one has to be careful what is said.
I have had inspections where the NM is on the bottom of the joists in an unfinished basement and I have mistakenly said "if it had a drop ceiling it would have been ok"... only to return to find a suspended ceiling in rooms that had no wall receptacles whatsoever,... now what do we have ?
What if you had a finished basement with open joists above but no drop ceiling?
 
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