Thread: Just wondering

Quick question my inspection brothers,
Is NM sheathed wiring allowed in the crawlspace or does it need to be BX or routed in conduit Your prompt response would be greatly appreciated!!

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Check your local code

Its allowed in my area.

It depends.

See Article 334 for starters..link below is to California's version of the NEC.

RealRead Viewer : CaliforniaÂ*ElectricalÂ*CodeÂ*2010

The answer is not a blanket yes or no. What are the conditions in the crawlspace? Under what code was it installed? Prohibited installations have changed under the NEC. I believe the CEC is taken from the NEC with some changes.

As mentioned, depends on the local code. In Edmonton as long as not in earth contact, definitely yes.

This is a bit loosely enforced and really an AHJ call. The code requires that NM wires be "protected" within 5', ( maybe 10' ? ) of crawl access only. It can be accomplished by runner boards next to them, keeping them under the joist surfaces in that area or conduit / BX. In some areas it is ignored altogether.

Apologies for my earlier post. I was thinking attic crawl space. It is allowed almost anywhere in residential construction as long as it is not subject to physical damage.

Most crawlspaces would be damp locations, correct?

That is, other than crawlspaces serving as return air plenums.

- Location, Damp. Locations protected from weather and not subject to saturation with water or other liquids but subject to moderate degrees of moisture. Examples of such locations include partially protected locations under canopies, marquees, roofed open porches, and like locations, and interior locations subject to moderate degrees of moisture, such as some basements, some barns, and some cold-storage warehouses.

- Location, Dry. A location not normally subject to dampness or wetness. A location classified as dry may be temporarily subject to dampness or wetness, as in the case of a building under construction.

- Location, Wet. Installations underground or in concrete slabs or masonry in direct contact with the earth; in locations subject to saturation with water or other liquids, such as vehicle washing areas; and in unprotected locations exposed to weather.

NM in a crawl space ?
Thats a loaded question here !
Some here will automatically state that Most if not all crawl spaces are damp locations.
They base this on their own location. Others will say they are not, there agin based on their location.
I will say it depends on the crawl space. I have been in many in my area that are so dry they are dusty! Then I've been in some that were like a swamp.

I have seen some drive in basement garages with ten foot ceilings that were like ponds. So I think it all depends on the area and if it was allowed when installed and grandfathered. I think it's a good thing for everyone that we are not required to change stuff in our home to keep up with code unless we make changes, repairs or upgrades.

Originally Posted by ken horak

Others will say they are not, there agin based on their location.

You noticed that I stirred the pot and put up the recipe, but did not comment on how to cook it.

Originally Posted by Jerry Peck

You noticed that I stirred the pot and put up the recipe, but did not comment on how to cook it.

Yes I did notice

Ya, I remember going back and forth with the what is damp with you JP
I submit that vented attic spaces are more damp than most crawls.
Answer for the OP, yes NM is allowed in attics unless specifically prohibited by local.

I inspected a modular home today that was put on a new crawl. There was plenty of NM from the factory in the floor joists. It was dry under there... how dry U axed?
It was so dry,, saw a rat dead of dehydration while pulling a knife on a mouse for a piece of cheese. It's true.

It was already mentioned the cables need mechanical protection around scuttle holes (peoples put shet up there is guess). The AHJ may enforce derating rules due to heat.
As for crawls, it is an AHJ determination if/where mechanical protection is needed.
Remember that NM cannot be stapled to the bottom of joists unless the cable contains (3) # 8ga conductors or (2) # 6's per NEC. Going by my poor memory... hope that code hasn't changed but I trust I'll know shortly if not!

As far as U HI's, how are you to know whether or not the AHJ had allowed anything at all? Perhaps it was done w/o permits?. I suppose you can call out those gray issues as possibilities to be confirmed by the local AHJ.
I'm not a HI, so I'm just wondering how it's handled by most of you.

Originally Posted by bob smit

Ya, I remember going back and forth with the what is damp with you JP
I submit that vented attic spaces are more damp than most crawls.
Answer for the OP, yes NM is allowed in attics unless specifically prohibited by local.

I inspected a modular home today that was put on a new crawl. There was plenty of NM from the factory in the floor joists. It was dry under there... how dry U axed?
It was so dry,, saw a rat dead of dehydration while pulling a knife on a mouse for a piece of cheese. It's true.

It was already mentioned the cables need mechanical protection around scuttle holes (peoples put shet up there is guess). The AHJ may enforce derating rules due to heat.
As for crawls, it is an AHJ determination if/where mechanical protection is needed.
Remember that NM cannot be stapled to the bottom of joists unless the cable contains (3) # 8ga conductors or (2) # 6's per NEC. Going by my poor memory... hope that code hasn't changed but I trust I'll know shortly if not!

As far as U HI's, how are you to know whether or not the AHJ had allowed anything at all? Perhaps it was done w/o permits?. I suppose you can call out those gray issues as possibilities to be confirmed by the local AHJ.
I'm not a HI, so I'm just wondering how it's handled by most of you.

The requirement for running boards, being run through bored holes has only begun since the adoption of the 2008 NEC, lots of installations were done prior to that change.

334.15(C) 2008 edition

(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 6 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............................................ ................................
.................................................. ...................................
.................................................. ...................................

Rollie, just adopted 2008 NEC??
I just opened a 1999 cause it was closest to my chair... NEC art 336 part B, same thing, and I know it goes way back to when I was green.

Originally Posted by bob smit

Rollie, just adopted 2008 NEC??
I just opened a 1999 cause it was closest to my chair... NEC art 336 part B, same thing, and I know it goes way back to when I was green.

Crawl spaces were added in '08.

Spaces is confusing when posted on this forum because different locals may have different terms. Around these here parts we call "crawl space" under the home. We just call roof area "attic". Both use NM and the like since it's been available.