How far from the end of a 2×12 or 2×10 floor joist can I drill a hole?
NEC 502.8 does not give this answer, only that you have to be 2" above or below the edges, not in what part of the span it has to be in.
Electrical – Where in the span of a floor joist can I drill holes to run wiring
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Disclaimer: We bring in outside contractors for our electrical installs, so I can give you some general tips, but I'll defer to others that may know more about this specific problem.
In general, joists, and any lumber supporting a load on its side, will lose much of its carrying capacity when it is drilled or cut on the top or bottom. For passing through the joists, you should make the hole in the center (between the top and bottom) of the joist, and make it the smallest hole that allows the wire to pass freely.
Having a double joist running beneath a wall means that the wall and joists are designed to be load bearing. So because of this, unless someone with more structural knowledge says it's ok to drill a hole, I'd avoid it.
While I can't think of a good way to get the wire into the wall, you could install your outlet on an adjacent wall, or you could go for a floor mounted outlet as a last resort:
I spoke to my structural engineer and the answer is that it depends on the depth of your joists. In my case, where I have 2x10 joists there is no problem with a small (1-inch diamater) hole on or near the area where the joist is bearing on its support beam. Basically the same notching and boring rules apply at the end of the joist: 2 inches from top or bottom, etc..
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Best Answer
The rules that I know for holes (not notches) are to keep your hole in the center of the joist when possible (top to bottom) or at least 2" from an edge, round, with a diameter less than 1/3 of height of the joist. Once you follow those, I don't believe there's a restriction on how close or far from the end of the joist you can install the holes. Personally I would keep the hole at least the length of one hole diameter (or 2" for small holes) away from the end of the joist, but there isn't anything in the building code I see requiring that.