I built a leanto on the front of my pole barn. It's 3 sided, so the
horses can get shelter when the weather is nasty. At the last minute
I decided to add a light. That required getting the cable (NM Romex)
thru the wall from inside the barn. This left me two options.
1. Drill a home thru the top 2x6, and thru the pole barn steel siding.
2. Run the cable thru one of the ribs on the underside of the roof
I chose the second option for two reasons. First, it was less work,
since there is a rib every 10 inches, so there were plenty to choose
from. Secondly, drilling thru steel siding is going to leave a sharp
edge on the steel where the cable runs, which could eventually
puncture the cable.
As far as safety, I think I chose the right way, but is it legal
acording to the NEC?
(I'm not too worried about this, it wont be inspected, I'm just
On Thu, 22 May 2008 04:13:47 -0500, firstname.lastname@example.org wrote:
I will assume the "Romex" is type UF and agree your idea is OK. If it
went through a bored hole in steek it would nee additional protection
pipe or something (meaning a listed raceway used as a sleeve).
You have the serious danger identified, a cable rubbing on a sharp
I feel your pain!!! I've been in the electrical contracting business for
over 35 years, and I'm still asking the same questions you are. I believe
the main concern in agricultural buildings is combustible dust. They make a
tight fitting gland connector to use with UF that would prevent dust from
entering boxes and fittings
My town has quite a few farms and stables. It amazes me what these farmers
do when they wire up things themselves. I saw a dog kennel and stable wired
up with lamp cord a few years ago. Just last week I got a call about
converting a private in-ground pool to a public pool so the farmer could
have a camp for kids in the summer. In NJ an electrician must certify a
public pool every five years. I go to look at the pool and see that the
pump wiring is fed underground with Romex inside of greenfield. There were
junction boxes every 50' or so that were actually indoor metal time clock
enclosures. No greenfield connectors were used. No grounding. No pool
bonding. They will need to spend several thousand dollars to make the pool
safe and compliant.
While "basically" UF is similar to NM, it isn't the same as either (or
it wouldn't have a different designation). The "C" is for corrosive/wet
environment which the Code considers any barn to be, by definition.
That's the reason for the proscription against NM.
That is true for haymows and other areas for grain and similar storage,
true. It is not the reason for a livestock barn, however. They are, in
general, damp if not actually wet and the animal byproducts are quite
corrosive even in vapors as well as in the solid and liquid forms.
Hence, since the Code is written to cover all uses from the casual
pleasure horse barn of OP to the full-fledged production milking parlor
or farrowing house, it is written for the conditions that may be
expected in a "working" barn.
No sir the main concern in stock barns is that the environment is
inherently damp and corrosive because of the inevitable constant
presence of animal urine. If the man has been in the horse care
business for long he has already seen how fast any steel that is not
galvanized of otherwise corrosion protected will rust in a stock barn.
The paper filler used in Type NM cable will wick moisture into
electrical boxes and accelerate the corrosion of ordinary switches and
receptacles housed in them. Type NMC cable on the other hand is called
barn cable by those of us who go back far enough in the craft to
remember the use of that marking by manufacturers before the Type NMC
cable class was identified as a standard cable type. It is much the
same way some manufacturers now mark type AC cable that also has an
insulated green grounding conductor in it HFC meaning Health Facilities
Cable. But search far and wide you will not yet find that
classification in the UL building materials list or other listings of
electrical materials because as yet that marking is not yet accepted by
the consensus code making and standards bodies. Ordinary electrical
materials are generally unsuitable for use in stock barns because in
order to keep the installation safe for humans and animals for the
entire useful life of the building materials, including cable, that is
suitable for damp and corrosive locations must be used.
"This alternating current stuff is just a fad. It is much too dangerous
Another thing is that NEC Article 334 requires that when NM is used
outside of a dwelling unit, it needs to be covered by a 15 minute
(fire) finish like drywall. So that includes barns and detached
Actually Wayne you have that backwards. The building code requires the
fifteen minute rated noncombustible finish in multiple dwellings and
several other occupancy classifications because the smoke contributed
rating of such cable is too high for buildings with lots of people at
risk. There is no such requirement in single family homes or stock
barns except in a few locations like San Fransisco.
San Fransisco's precautions regarding stables come from a fire that
occurred decades ago in a stable in Golden Gate park. There were dozens
of horses trapped by the fire and citizens could hear their death
screams for many blocks away. The sense of horror that instilled in the
public there at that time caused the city to require all horse barns in
the city limits to be protected by automatic fire sprinklers. As far as
I know there is no such requirement for sprinkler protection in single
family homes or even multiple family dwellings in that city to this day.
Maybe if dying people would scream as loud as a horse does... but I
"This alternating current stuff is just a fad. It is much too dangerous
Exercepts from Paragraphs 334.10 and 334.12 of the 2008 NEC (same as
334.12 Uses Not Permitted.
(A) Types NM, NMC, and NMS. Types NM, NMC, and NMS cables shall not
be permitted as follows:
(1) In any dwelling or structure not specifically permitted in
334.10(1), (2), and (3).
334.10 Uses Permitted. Type NM, Type NMC, and Type NMS cables shall be
permitted to be used in the following:
(1) One- and two-family dwellings.
(2) Multifamily dwellings permitted to be of Types III, IV, and V
construction except as prohibited in 334.12.
(3) Other structures permitted to be of Types III, IV, and V
construction except as prohibitied in 334.12. Cables shall be
concealed withing walls, floors, or ceilings that provide a thermal
barrier of material that has at least a 15-minute finish rating as
identified in listings of fire-rated assemblies.
So the NEC doesn't have any requirements about finish rating for NM
cable used in dwellings, although the building code probably does.
However, outside of dwellings, 334.10(3) of the NEC requires that NM
cable be covered with a 15-minute finish rating. So if you want to
use NM cable in your barn, you need to cover it with drywall or 1x
boards, just like you need to cover plastic foam insulation. The same
goes for a residential detached garage, a commercial building, etc.
I believe this requirement is fairly new and is a replacement for a
requirement limiting NM cable to structure of 3 stories or less. I
guess both the manufacturers and the responsible NEC committee felt
this was an acceptable trade off. I'm not 100% sure about this
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.