Thread: Bored holes for "home runs"

I understand the following code for boring holes thru floor joists:

"The diameter of holes bored or cut into members shall not exceed
one-third the depth of the member. Holes shall not be closer than 2
inches to the top or bottom of the member, or to any other hole located
in the member. Where the member is also notched, the hole shall not be
closer than 2 inches to the notch."

My question is how many 3/4"or 1" bored holes, for home runs, can you have in the outer 1/3 of a 2x10 joist? I have seen some floor joists that look like swiss cheese.

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(red text is mine)

Originally Posted by James Savage

I understand the following code for boring holes thru floor joists:

"The diameter of holes bored or cut into members shall not exceed
one-third the depth of the member. Holes shall not be closer than 2
inches to the top or bottom of the member, or to any other hole located
in the member. Where the member is also notched, the hole shall not be
closer than 2 inches to the notch."

My question is how many 3/4"or 1" bored holes, for home runs, can you have in the outer 1/3 of a 2x10 joist? I have seen some floor joists that look like swiss cheese.

Now does that mean you could bore it full of holes spaced 2" edge-of-hole-to-edge-of-hole? Well ... that *IS* what it says.

Originally Posted by Jerry Peck

(red text is mine)


Now does that mean you could bore it full of holes spaced 2" edge-of-hole-to-edge-of-hole? Well ... that *IS* what it says.

Yeah the engineers have it there. Personally I hate the idea that you can drill , as was said, these joists to swiss cheese and I only have to question......Huh. I guess they must know what they are doing.

I've seen a number of joist drilling guides over the years and most all of them agree on a couple of things, different info on others.

Always agree
No hole edge within 2" of the top/bottom edge of the joist.
Hole diameter not more than 1/3 of the ACTUAL depth.
No notches in middle third of joist

Sometimes agree
Holes of the same diameter must be 3 hole diameters apart (ie 1 inch holes are 3 inches apart between edges) Holes of different sizes are 3 diameters of the largest hole apart
Hole centers must be joist depth apart
Hole edges and notches must be 2" apart
No holes in middle third of joist (California Bldg Code)
Notches not more than 1/3 joist depth long
Notches not more than 1/6 joist depth deep

Some local rules help limit the swiss cheese look. See what your local rules are