Yes, you can run more than one wire through a 1" hole. Any more than three you might start peeling the outer insulation off. Just make sure that when you drill your holes you stay in the center of the joists.

I'm no builder, but remember that joists are integral to the structure of the house. I'd make the holes as small as you can get away with, and try to put the holes (vertically) in joist centers.

From my research, there are recommendations on how large the holes and/or notches can be. And if there's more than one hole (for example, another hole or notch elsewhere in that joist) that also counts toward the total. There are other limitations as well (this is just a start!)....so again, please keep your holes centered and as small as possible.

good luck,

-k2

Thanks for the info guys. I try to keep as few holes as possible but i found if i drill a 1 inch hole i can run 2 or 3 cables versus 2 or 3 small cables. These are old 2x8 beams, im not to worried about them loosing support. The only one i had to place the whole lower than center was on a 4x8 beam as the other side is concret. But I reinforced the area with some wood to compensate it.

Thanks for the help guys!