Romex Stapled to Joists

We have some Romex wiring in the unfinished section of our basement which runs at right-angles to the joists above. It is secured with staples on the bottom of the joists, which I understand to be against code for wire sizes less than 6-2 or 8-3. I have a few questions relating to this situation, and would be grateful for some guidance...
1/ I understand that if I install running boards, the Romex can be stapled to those, and everything will be code. Would it be sufficient for this boards to go between the inside faces of the joists, perhaps affixed with pocket hole screws in their ends, or must they actually run below the bottom of the joists? Also, since code only demands stapling to the running boards every 4 feet or so, how does this provide any more support than stapling to each joist, given that the joists are considerably closer than 4 feet?
2/ Would it also meet code to cover the wiring, perhaps with some sort of partial plywood ceiling, mounted on but spaced away from the joists? This would ensure that the wiring would be inaccessible, but I'm not sure it would remove the requirement for no stapling.
3/ How long has the no-staples rule been around? All this wiring was done by reputable licensed electricians, as far as I can tell, and so was it installed prior to this rule being established? Or the rule more honored in the breach than the observance?
4/ Why exactly is this rule in place? I've read a couple of theories, namely that it is to prevent sagging of the cables, or that it is to prevent people hanging things on them. The first seems strange, as stapling to each and every joist provides more support than would be provided, say, by stapling every 4 ft or so on a running board. And if the second theory is correct, simply blocking off access would avoid this danger.
As I say, any comments would be welcome.
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while it is wrong, it never seems to matter. Any new wiring should be proper, but forget about old wiring.
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You are correct.

That, I think, would be a question for your local electrical inspector. The NEC does not specify precisely how the running boards must be attached, but the term *implies* that the Code intends that those boards "run" across multiple joists.

It doesn't, but that doesn't matter, either. The prohibition against stapling to the bottoms of the joists, without running boards, is intended to protect the cable from physical damage, and isn't related to supporting it.

The NEC says you can't staple NM cable across joists in unfinished basements. Whether the plywood ceiling is sufficient to cause that portion of the basement to be considered "finished" is another question for your local electrical inspector.

It's in the 1984 Code. Don't know if it's older than that or not.

That may depend on how long it's been since the wire was installed, but if it was any time since 1984, it definitely did not meet Code at the time (and probably didn't before then). The rule is very often ignored.

Mostly to prevent hanging things on them.

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wrote:

Get some cheap 2x4's. Cut a piece to fit between the joists for each joist and nail or screw the pieces flat, above the wire. The cost will be small for cheapy 2x4s and some fastners. You will then be up to code, and these blocks will also make your floors a little stronger too. This will be a bit time consuming, but the price is right, it will meet code, and you dont have to mess with the wiring at all. It dont matter what construction method is used as long as the wire has solid wood behind it. This keeps children (and alcoholic adults) from doing chin-ups on the wire, or using it to hang their mother-in-law :)
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wrote:

You can place the "running boards" along side of the Romex. The idea is to prevent someone from putting a wire hanger directly onto the Romex. Staple as much as needed to prevent the wire from sagging.

You need to protect the wire against hanging something on it.

The rule is for safety. Sagging wire may or may not be a safety issue. You probably should talk to a (local) electrician to know which rules are strictly enforced and why. It is always a good idea to follow all the NEC, although this will increase cost it is well worth it.

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Phisherman wrote:

That's it exactly, as Phisherman notes. As a side comment, I will note that in the Navy (where we have our own electrical code), we use wireways to support cable runs up against the deckhead. The hanger bars are spaced about 50 cm apart on average, and I figure about a third of my day is spent telling sailors to f**king well stop hanging shit off them, or trying to do chin-ups, or grabbing them when the ship takes a roll... this is one aspect of the code I wish the Navy had adopted.
Yours aye, W. Underhill
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How high is the ceiling?
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