NM in drop ceiling

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elecmen

Senior Member
Location
NH
Occupation
Electrician
Is it code compliment to install NM in a drop ceiling in residential and staple it to the underside of the floor joists
 

Ponchik

Senior Member
Location
CA
Occupation
Electronologist
Per code, In dwelling drop ceiling YES but stapled under the joist NO. Unless the NM cable is 8/3 or 6/2 and larger or for smaller NM cables you need running board.

On a second note, I never understood why the NM cable can not be stapled to the underside of the joist. I don't see the difference between it and going through bored holes of the joist.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
On a second note, I never understood why the NM cable can not be stapled to the underside of the joist. I don't see the difference between it and going through bored holes of the joist.
Not as an immediate safety feature, but to facilitate installing a flush ceiling without having to redo the wiring or expose it to screws and nails?
It is arguably more exposed to damage from objects, etc. than it would be when recessed above the bottom of the joists.
 

Ponchik

Senior Member
Location
CA
Occupation
Electronologist
Not as an immediate safety feature, but to facilitate installing a flush ceiling without having to redo the wiring or expose it to screws and nails?
It is arguably more exposed to damage from objects, etc. than it would be when recessed above the bottom of the joists.

I think it is a "Physical damage" and or "safety" issue because it is required to be run through bored holes in the crawl space. Now who would install a ceiling on the bottom of the floor joists in the crawl space?
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
It is to protect smaller cables from the physical damage of hanging objects from the cables in basements, and from being snagged on passersby in crawlspaces.
 

Gregg Harris

Senior Member
Location
Virginia
Occupation
Electrical,HVAC, Technical Trainer
Is it code compliment to install NM in a drop ceiling in residential and staple it to the underside of the floor joists

300.4 (C)
(C) Cables Through Spaces Behind Panels Designed to Allow Access. Cables or raceway-type wiring methods, installed behind panels designed to allow access, shall be supported according to their applicable articles. Cable- or raceway-type wiring installed above suspended ceilings with lift-up panels must not be laid on the suspended ceiling so as to inhibit access. Such wiring is required to be supported according to 300.11(A), 300.23, and the requirements of the article applicable to the wiring method involved.

334.30 Securing and Supporting.
Nonmetallic-sheathed cable shall be supported and secured by staples, cable ties, straps, hangers, or similar fittings designed and installed so as not to damage the cable, at intervals not exceeding 1.4 m (4? ft) and within 300 mm (12 in.) of every outlet box, junction box, cabinet, or fitting. Flat cables shall not be stapled on edge.

Sections of cable protected from physical damage by raceway shall not be required to be secured within the raceway.
 

jusme123

Senior Member
Location
NY
Occupation
JW
It is to protect smaller cables from the physical damage of hanging objects from the cables in basements, and from being snagged on passersby in crawlspaces.

they should allow an exception if a drop ceiling is installed in a basement
 

Ponchik

Senior Member
Location
CA
Occupation
Electronologist
So when you guys run some NM cable across a drop ceiling, you drill holes through every joist? Sure you do. :happyno::lol:

I don't.

I would rather install a running board if I have to, otherwise it will get nailed to the bottom of the ceiling/floor joist. I know it is a violation but I don't see any harm and I don't see any difference between installing it at the bottom or going through a joist.
 
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