I'm re-wiring some outlets etc. in an old house I own. The basement has an
open ceiling and the old wiring is stapled along the bottom surfaces of the
joists to get to the service panel.
For the new wiring, it is okay to staple the new wires the same way along
the bottom surfaces of the joists adjacent to the existing wires that are
already stapled there, or does the new wiring need to go through the joists?
And, for stapling wires in general, is it okay to staple two runs of wire
using one staple, or does each run of wire have to be stapled separately?
I am trying to find out what the National Electrical Code (or whatever the
national code is for the U.S.) says for both of these situations, but I
can't seem to find anything on the Internet.
No, yes, but...
Code prohibits exposed surface-mount wiring in habitable space. The
existing isn't up to current Code either, of course. New should
either be in conduit if run under or through or have a protective 1x
on either side of the run to make a (upside down) cable tray for the
protection is also still (I believe) compliant.
AFAIK, it's still ok if use properly sized staples.
Just out of curiosity, does this follow the current derating rule
about number of wires in a conduit? Say if you have three 14AWG 2-
wire w/ ground cables stapled together, then that would count as 6
current-carrying conductors in the same conduit, etc?
Yes, that's right, derating would apply.
But for the purposes of derating, you can start with the 90 degree
ampacity of the conductors (for modern NMB), although the final
ampacity can not exceed the 60 degree rating or for most circuits the
small conductor limits (15 amps for #14, 20 amps for #12, 30 amps for
#10). So the upshot is that unless you have 10 or more current
carrying conductors, the #12 is still good for 20 amps and the #14 is
still good for 15 amps.
I just found a cool website that answers the question about wiring in an
unfinished basement. I'm still searching regarding the stapling question
and whether there is a code about whether 2 or more NM runs can be stapled
with one staple.
The cool part about the website that I found is that it provides direct
links to the National Electrical Code.
Here's the website link I found regarding the basement wiring:
Their main website is:
As long as you don't squeeze the conductors, it should be fine to put
two cables under one staple. For example, the insulated staple gun I
use specifically says it is good for (2) 14/2 or (2) 12/2, although
only one 14/3 or 12/3, since they are typically round.
One thing to know is that if you staple them together for a run of
over 24", then most would consider them "bundled" and so derating
would apply. However as my other post mentions, for small conductors
in NMB cable, this has no effect until you reach 10 current carrying
The issue you raise is whether one can use NEC Table 310.17 for
ampacity (Allowable ampacities ... in Free Air) as opposed to Table
310.16 (Allowable Ampacities ... in Raceway, Cable, or Earth).
The issue I'm referring to is when the derating factors in Table
310.15(B)(2)(a) apply, and then whether the derating factors make any
difference, given the restrictions in 240.4(D) "Small Conductors".
So far, I haven't found the answers in the B&D book. It does say in the
2-page section on common code requirements that one should not staple wires
to the bottom of joists. But, it doesn't elaborate on what the options are
for various wire sizes etc. I haven't found anything yet in the book
regarding the question of whether 2 or more NM wire runs can be stapled with
the same staple.
It doesn't matter what the NEC says UNLESS your
local codes say to adhere to the NEC and have not
added their own little goodies to it. Call your
code enforcement office; only they have the final
answer for you, regardless of waht anyone here
Through the joist is an option, often the best choice. You can nail a
furring strip across the joists then attach the Romex to that. Or,
you can use conduit across the bottom of the joists. If a clothes
hanger (or work light) can be hooked onto the wire with the wire
providing the support, then it is not properly installed.
You can staple multiple wires. There are various size staples.
Careful, I had an inspector fail my rough inspection because I had
stapled the cables to the studs with wiring stapler. He said they were
not UL listed. I showed him the box with the UL seal, and that just
pissed him off and he said I still couldn't use them because they just
weren't safe. (Why didn't he say that to begin with instead of lying to
me about UL?)
I had to pull them all out and use plastic staples. It was a small job,
and it was easier to do that than to appeal to a supervisor who might
have also shot me down -- they don't like homeowners doing their own
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