05:00AM | 02/18/07
Member Since: 02/17/07
7 lifetime posts
I'll be wiring my workshop under the guidance of the electrical sub that's doing our new house. I've done several smaller wiring projects over the years. But, to keep me from unnecessarily bugging him for advice, I have a couple of questions so far.

When routing the sheathed electrical cable in the attic, (Wood framing), what's the best way? Is it normal practice to just run it directly across from junction box to junction box or should the wiring be secured along the joists and then across to the next junction box? Should I drill 3/4" holes in the joists instead of laying the wiring on top?

It seems that running it directly to the boxes would save on excess wiring, but running it along the joists and then across to the boxes would be neater.




06:12AM | 02/18/07
Member Since: 04/25/05
1915 lifetime posts
The section on NM (sheathed electrical cable) cables in attics refers to this section.

"320.23 In Accessible Attics

Type AC cables in accessible attics or roof spaces shall be installed as specified in

320.23(A) and (B).

(A) Where Run Across the Top of Floor Joists Where run across the top of floor joists,

or within 2.1 m (7 ft) of floor or floor joists across the face of rafters or studding, in attics

and roof spaces that are accessible, the cable shall be protected by substantial guard strips

that are at least as high as the cable. Where this space is not accessible by permanent

stairs or ladders, protection shall only be required within 1.8 m (6 ft) of the nearest edge

of the scuttle hole or attic entrance.

In accessible attics, Type AC cable installed across the top of floor joists or within 7 ft

of the floor or floor joists across the face of rafters or studs must be protected by guard

strips. Where the attic is not accessible by a permanent ladder or stairs, guard strips are

required only within 6 ft of the scuttle hole or opening.

(B) Cable Installed Parallel to Framing Members Where the cable is installed parallel

to the sides of rafters, studs, or floor joists, neither guard strips nor running boards shall

be required, and the installation shall also comply with 300.4(D)."


(D) Cables and Raceways Parallel to Framing Members and Furring Strips In both

exposed and concealed locations, where a cable- or raceway-type wiring method is

installed parallel to framing members, such as joists, rafters, or studs, or is installed

parallel to furring strips, the cable or raceway shall be installed and supported so that the

nearest outside surface of the cable or raceway is not less than 32 mm (1 1 / 4 in.) from the

nearest edge of the framing member or furring strips where nails or screws are likely to

penetrate. Where this distance cannot be maintained, the cable or raceway shall be

protected from penetration by nails or screws by a steel plate, sleeve, or equivalent at

least 1.6 mm ( 1 / 16 in.) thick.


06:47AM | 02/18/07
Member Since: 02/17/07
7 lifetime posts
Thanks Bill!

Would fold-up attic stairs be considered "permanent"?

There is very little room up there because of the truss supports, so there will just be a small area for storage near the scuttle hole no real "walking around" to speak of.



10:51AM | 02/18/07
Member Since: 04/25/05
1915 lifetime posts

Would fold-up attic stairs be considered "permanent"?"

Those are the gray area. In one part of the country they might be, not in another.

In general I would make it neat and logical, while not wasting a unusal amount of coper.

In general I would run along the trusses. Or at one or two areas nail in some 1x4 running bards (or untility 2x4" might be cheaper) at right angles to the trusses.

But say you have a kitchen in one corner diagonaly oposite the panel.

Since you have a large number of loads in the one area then run a running board diagonly across the trusses. and you can pick up other near by circuits at the same time.
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