HOLES IN 2" X 8" FLOOR JOIST

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timmermeier

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alton il
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electrician
I WANT TO DRILL 1" HOLES IN A 2" X 8" FLOOR JOIST 6" APART 3" FROM THE BOTTOM OF THE JOIST AND 12" FROM THE END OF JOIST, HOW MANY CAN I DRILL IN A JOIST ?
 
Generally speaking, you may drill through the center third in both directions.

That works for your 3" up from the bottom, but not your 12" in from one end.
 
LarryFine said:
Generally speaking, you may drill through the center third in both directions.

That works for your 3" up from the bottom, but not your 12" in from one end.
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I think you have it a little wrong, Larry.
The code says that you cannot make notches in the center third (since they would reduce the beam bending strength in the most heavily loaded part of the beam. But holes, which do not occupy the least loaded center of the beam height, are allowed.
But holes are also allowed outside the center third, as long as they meet the vertical spacing and distance from the end criteria.

Here is a good summary of the applicable industry standard rules (not from the electrical code.)

So, I think that with the spacing he proposed, the OP's answer is "as many as will fit", limited by the length of the beam.
 
Structural floor members shall not be cut, bored or notched in excess of the limitations specified in this section. See Figure R502.1.11.
0cc50c4b-2b36-4bc1-bdb6-81661f18c032.jpg

For SI: 1 inch = 25.4 mm.
FIGURE R502.1.11 [IRC 502.8]
CUTTING, NOTCHING AND DRILLING
R502.1.11.1 [IRC 502.8.1] Sawn lumber.
Notches in solid lumber joists, rafters and beams shall not exceed one-sixth of the depth of the member, shall not be longer than one-third of the depth of the member and shall not be located in the middle one-third of the span. Notches at the ends of the member shall not exceed one-fourth the depth of the member. The tension side of members 4 inches (102 mm) or greater in nominal thickness shall not be notched except at the ends of the members. 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 (51 mm) 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 (51 mm) to the notch. R502.1.11.2 [IRC 502.8.2] Engineered wood products.
Cuts, notches and holes bored in trusses, structural composite lumber, structural glue-laminated members or I-joists are prohibited except where permitted by the manufacturer's recommendations or where the effects of such alterations are specifically considered in the design of the member by a registered design professional.


It is a Building Code issue. Go on-line and search for International Residental Code (IRC) and it will give you alot of more information. The IRC also have the requirements for smoke alarms and CO alarms.

Have a great Holiday.

Bill
 
GoldDigger said:
I think that with the spacing he proposed, the OP's answer is "as many as will fit", limited by the length of the beam.
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I've read in some official building code spec that holes have to be "3 diameters apart" but I would have to search and find that.

So if he was drilling 1-inch holes there would have to be at least 3 inches of wood between the holes.
 
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