Is NM allowed in Crawl Spaces?

[Accurate1]

I am a home inspector in New Jersey.

Today I attended a CEU class for home inspectors.

The instructor is an electrical inspector who provided a large quantity of useful information.

One thing he did say that I do not remember hearing before is that the NEC has always considered crawl spaces to be a damp location and that NM wire was NEVER allowed to be used in crawl space even when properly secured to the structure of the home.

In my area just about every crawl space has NM wire and every home inspector I spoke with indicates they see more problems with metal cable in crawl spaces than any other due to rust.

Does anyone have a specific reference on this one?

 

[iwire]

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.

 

[infinity]

NM cable is specifically permitted in crawl spaces.

334.15 Exposed Work.
In exposed work, except as provided in 300.11(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, or other approved means. Where passing through a floor, the cable shall be enclosed in rigid metal conduit, intermediate metal conduit, electrical metallic tubing, Schedule 80 PVC conduit, or other approved means extending at least 150 mm (6 in.) above the floor.
Type NMC cable installed in shallow chases or grooves in masonry, concrete, or adobe, shall be protected in accordance with the requirements in 300.4(F) and covered with plaster, adobe, or similar finish.
(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. NM 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 NM cable sheath shall extend through the conduit or tubing and into the outlet or device box not less than 6 mm (? 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 conductor.

 

[iwire]

NM cable is specifically permitted in crawl spaces.

Rob, I have no issue with NM in most crawls and basements but I disagree that 334.15(C) gives permission to run NM in basements and crawls that are in fact damp.

Truthfully I have no issue with NM in damp locations either other than the code requirements.

 

[K8MHZ]

Rob, I have no issue with NM in most crawls and basements but I disagree that 334.15(C) gives permission to run NM in basements and crawls that are in fact damp.

Truthfully I have no issue with NM in damp locations either other than the code requirements.

NM seems to be remarkably suited for what it's not listed for. I have seen miles of the stuff used outdoors and even after years of exposure it was just fine.

That being said, I am curious as to what criteria is needed to be met in order to get a wet or damp location listing.

 

[infinity]

Rob, I have no issue with NM in most crawls and basements but I disagree that 334.15(C) gives permission to run NM in basements and crawls that are in fact damp.

Truthfully I have no issue with NM in damp locations either other than the code requirements.

I agree, but the NEC definition of Location, Damp is lousy. The definition doesn't mention crawl spaces and Article 334 says that it can be installed in crawl spaces. I would have a hard time seeing a crawl space actually being considered a damp location.

 

[Dennis Alwon]

I have seen water dripping from the insulation under a house so without a doubt some crawls can be damp but I have never seen an inspector turn it down. IMO, the code either should change and clarify this in some way. I have seen nm cable underground working for 20 years.

I did an addition one time and I used a blueboard to float thru the water standing under the house-- I thing there was over 3" of water under there- and I don't mean just in one spot.

 

[iwire]

but the NEC definition of Location, Damp is lousy.

I agree, it is.

I would have a hard time seeing a crawl space actually being considered a damp location.

One under a modern home, yeah I agree.

One under an old home could be very damp, dirt floor, no vapor barrier etc. But I would never want to call it one and I would run NM.

 

[jxofaltrds]

I am a home inspector in New Jersey.

Today I attended a CEU class for home inspectors.

The instructor is an electrical inspector who provided a large quantity of useful information.

One thing he did say that I do not remember hearing before is that the NEC has always considered crawl spaces to be a damp location and that NM wire was NEVER allowed to be used in crawl space even when properly secured to the structure of the home.

In my area just about every crawl space has NM wire and every home inspector I spoke with indicates they see more problems with metal cable in crawl spaces than any other due to rust.

Does anyone have a specific reference on this one?

The NEC does not say that a crawl is concidered damp.

Rob, I have no issue with NM in most crawls and basements but I disagree that 334.15(C) gives permission to run NM in basements and crawls that are in fact damp.

Truthfully I have no issue with NM in damp locations either other than the code requirements.

I agree.

334.10 allows NM in the structure.

If the crawl is truely damp you should be worrying about the structure not the NM.

 

[renosteinke]

Welcome to the brave new world of the 2008 NEC.

Until then, it was clear; NM could be used in damp locations, so the issue of crawl spaces never arose.

With 2008, we find that NM is generally allowed in damp locations, but then we read a bit further, where it specifically says that NM-A and NM-B can be run only in dry locations. NM-C -which is supposed to have a plastic wrap rather than the paper one around the ground wire - simply does not exist.

Suddenly the home inspection community discovered this 'defect.' Any evidence of moisture anywhere in a crawl space makes the whole place a 'damp' location in their book, let alone where you might find standing water or mold.

NM has "always" been forbidden in crawl spaces? I think not. Indeed, I have yet to see a house with a crawl space, and NM as the wiring method, where the NM does not pass through the crawl space. Millions of homes and thousands of contractors can't all be in the wrong.

IMO, it's simply bad code, and I sincerely hope that the 2011 edition sorts this out. Alternatitively, how about just getting the paper out of NM?

Off on a tangent, even the NEC committee that specifically deals with NM has a schitzo attitude towards the material. It's proven 'safe,' so let's allow it in commercial buildings .... wait, it's not 'safe,' let's get it out of crawl spaces .... etc. Then there's another committee that thinks the stuff is so hazardous it needs special circuit breakers.

I'm not surprised at the OP's introduction to the topic, though. The HI community is awash in folks who come down with 'attacks of the vapors' at the sight of a fuse box or knob & tube wiring. Show them an FPE or Zinsco panel, and you better have their medication handy.

 

[jxofaltrds]

Welcome to the brave new world of the 2008 NEC.

Until then, it was clear; NM could be used in damp locations, so the issue of crawl spaces never arose.

With 2008, we find that NM is generally allowed in damp locations, but then we read a bit further, where it specifically says that NM-A and NM-B can be run only in dry locations. NM-C -which is supposed to have a plastic wrap rather than the paper one around the ground wire - simply does not exist.

Suddenly the home inspection community discovered this 'defect.' Any evidence of moisture anywhere in a crawl space makes the whole place a 'damp' location in their book, let alone where you might find standing water or mold.

NM has "always" been forbidden in crawl spaces? I think not. Indeed, I have yet to see a house with a crawl space, and NM as the wiring method, where the NM does not pass through the crawl space. Millions of homes and thousands of contractors can't all be in the wrong.

IMO, it's simply bad code, and I sincerely hope that the 2011 edition sorts this out. Alternatitively, how about just getting the paper out of NM?

Off on a tangent, even the NEC committee that specifically deals with NM has a schitzo attitude towards the material. It's proven 'safe,' so let's allow it in commercial buildings .... wait, it's not 'safe,' let's get it out of crawl spaces .... etc. Then there's another committee that thinks the stuff is so hazardous it needs special circuit breakers.

I'm not surprised at the OP's introduction to the topic, though. The HI community is awash in folks who come down with 'attacks of the vapors' at the sight of a fuse box or knob & tube wiring. Show them an FPE or Zinsco panel, and you better have their medication handy.

As to the defect. What is the safety hazard? None.

What is being called out is a 'code' violation.

Home inspectors are trying to have it both ways. Being a generalist while playing expert.
BTW I do home inspections so I am not bashing the whole industry. Just those who are given bad information and pass that information along as the gospel.

As to the original post. What should be called out is the dampness in the crawl. If the HI has a concern as to the NM he should defer that to an electrician or electrical inspector for further review.

 

[Dennis Alwon]

This whole issue can be resolved by having the manufacturers use a 90C wire that is listed for damp location. They can still insists that romex cannot be installed in a wet location.

 

[cpal]

This whole issue can be resolved by having the manufacturers use a 90C wire that is listed for damp location. They can still insists that romex cannot be installed in a wet location.

I doubt that will happen as long as they mfg UF

 

[Dennis Alwon]

I doubt that will happen as long as they mfg UF

NM wouldn't be rated for UG and the NEC can make the manufacturers produce it. I agree it will probably never happen.