NM cable in unfinished basements. What does your AHJ do?

[brycenesbitt]

I'm trying to compile and read up on NM cable in unfinished basements.
Our local inspectors seem OK with NM in basements (ceiling or high up on wall) as long as it is not nailed to lower joist edges.
How about yours?

The code mentions a distinction between a dirt crawl and a unfinished (storage) basement. Is there any place the rules are different for the two types?


300.4 Protection Against Physical Damage. Where subject to physical damage, conductors, raceways, and cables shall be protected....

334.10 Uses Permitted. Type NM, Type NMC, and Type NMS cables shall be permitted to be used in the following except as prohibited in 334.12 [which does not seem to contain anything relevant]: (1) One- and two-family dwellings and their attached or detached garages, and their storage buildings. […]

(A) Type NM. Type NM cable shall be permitted as follows: (1) For both exposed and concealed work in normally dry locations except as prohibited in 334.10(3)....

334.15 Exposed work. In exposed work, except as provided in 100.11(A), cable shall be installed as specified in 334.15(A) through (C).

(A) To Follow Surface. Cable shall closely follow the surface of the building finish or of running boards.
(B) Protection from Physical Damage. Cable shall be protected from physical damage where necessary by rigid metal conduit, intermediate metal conduit, electrical metallic tubing, Schedule 80 PVC conduit,...,.other approved means.....
(C) In Unfinished Basements and Crawl Spaces. Where cable is run at angles with joists in unfinished basements and crawl spaces, it shall be permissible to secure cables not smaller than two AWG or three 8 AWG conductors directly to the lower edges of the joists. Smaller cables shall be run either through bored holes in joists or on running boards. Nonmetallic-sheathed cable installed on the wall of an unfinished basement shall be permitted to be installed in a listed conduit or tubing or shall be protected in accordance with 300.4. Conduit or tubing shall be provided with a suitable insulating bushing or adapter at the point the cable enters the raceway. The sheath of the nonmetallic-sheathed cable shall extend through the conduit or tubing and into the outlet or device box not less than 6 mm (1/4 in). The cable shall be secured within 300 mm (12 in) of the point where the cable enters the conduit or tubing. Metal conduit, tubing, and metal outlet boxes shall be connected to an equipment grounding connector complying with the provisions of 250.86 and 250.148.

 

[suemarkp]

Speculating here, but I could see a crawl space being considered a damp area (requireding UF cable) whereas even an unfinished basement is typically conditioned space and wouldn't be damp or as damp as a crawl space. Would depend on what part of the country you are in and humidity or water table levels. The thing that also seems to change by location is the definition of unfinished in regards to basements. For GFCI's, it is typically bare floors. For wiring methods, I"m not sure where the finished/unfinished line is. Carpet? Wall covering but open ceiling?

 

[augie47]

Just for reference, TN amended 334.15 to allow cables to be fastened to the bottom of joist in crawl spaces less than 4' 6" in height.

 

[Dennis Alwon]

Just for reference, TN amended 334.15 to allow cables to be fastened to the bottom of joist in crawl spaces less than 4' 6" in height.

North Carolina just deleted the word crawl spaces in (C)

 

[kwired]

Speculating here, but I could see a crawl space being considered a damp area (requireding UF cable) whereas even an unfinished basement is typically conditioned space and wouldn't be damp or as damp as a crawl space. Would depend on what part of the country you are in and humidity or water table levels. The thing that also seems to change by location is the definition of unfinished in regards to basements. For GFCI's, it is typically bare floors. For wiring methods, I"m not sure where the finished/unfinished line is. Carpet? Wall covering but open ceiling?

If it is truly damp whether or not NM cable is used should be low on the list of concerns of what that "damp" might do over time, both to the building materials and to healthy air quality.

 

[LarryFine]

North Carolina just deleted the word crawl spaces in (C)

And a half a million houses immediately dropped a couple of feet.

 

[brycenesbitt]

Ok, so is it OK to run NM between the floor joists or not?

Our crawls here are dry, and they're stuffed with NM cable that seems in fine shape, and MC cable that's either fine or rusty.

I guess the cases are:

• Dirt crawl, less than 5', open floor joists above
• High dirt crawl.
• Unfinished basement with walk-able height, open floor joists/wall cavities.
• Semi-finished basement with drywall or coverings.

 

[suemarkp]

I think you can always run along the side of a joist if >1.25" from a face, or through bored holes in the joists. Running along the bottom of joists is where the variables come in -- running boards with or without guard boards, just along the bottom if the cable is large enough and you meet the other restrictions. If you drill holes, put them in the middle of the joist -- not the lower or upper third. If the new OSB web type joists, they usually have marked knock outs in the wood where you can drill a hole (I don't think they actually knock out).

 

[retirede]

If the new OSB web type joists, they usually have marked knock outs in the wood where you can drill a hole (I don't think they actually knock out).

They do knock out if you hit them hard enough - it rarely looks pretty.
And I can’t remember the last time I saw an installation where the GC made sure the knockouts were lined up!

 

[Little Bill]

They do knock out if you hit them hard enough - it rarely looks pretty.
And I can’t remember the last time I saw an installation where the GC made sure the knockouts were lined up!

Yes, I finally gave up on trying to knock out the spots, looks like you shot it close range with a shotgun!
Also, the KOs go against what was said about not drilling in the lower 1/3 of the joist as that's where they are in some cases.

 

[brycenesbitt]

My AJH came back and said that the cables must be covered in unfinished basements unless they're 8 feet or more off the floor.
I have asked for a code reference.

For the notching issue, see:

Western Wood Products Association 522 SW Fifth Avenue Suite 400 Portland, OR 97204-2122

Home

Western Wood Products Association, representing Western lumber manufacturers.

www.wwpa.org

Document A-11/2017e/8-96, 2-97/15M
"NOTCHING & BORING GUIDE FOR FLOOR JOISTS & STUD WALLS IN CONVENTIONAL LIGHT-FRAME CONSTRUCTION "

 

[kwired]

My AJH came back and said that the cables must be covered in unfinished basements unless they're 8 feet or more off the floor.
I have asked for a code reference.

For the notching issue, see:

Western Wood Products Association 522 SW Fifth Avenue Suite 400 Portland, OR 97204-2122

Home

Western Wood Products Association, representing Western lumber manufacturers.

www.wwpa.org

Document A-11/2017e/8-96, 2-97/15M
"NOTCHING & BORING GUIDE FOR FLOOR JOISTS & STUD WALLS IN CONVENTIONAL LIGHT-FRAME CONSTRUCTION "

There is no 8 foot dimension mentioned in NEC for this sort of thing, just requirement to protect when subject to physical damage. That kind of means your AHJ interpretation is that anything below 8 feet is subject to physical damage.

 

[brycenesbitt]

There is no 8 foot dimension mentioned in NEC for this sort of thing, just requirement to protect when subject to physical damage. That kind of means your AHJ interpretation is that anything below 8 feet is subject to physical damage.

Yeah, got it.
Is there anything to point to in the NEC about "1.25" up from the joist" vs. "on the face of floor joists".

What does your AJH do?

 

[kwired]

Take a look at 300.4. and 334.15

Yeah, got it.
Is there anything to point to in the NEC about "1.25" up from the joist" vs. "on the face of floor joists".

What does your AJH do?