I have three floor joists that have approximately 1/2 inch hole in them less than 2 inches from the bottom. Is there a recommended fix or approved method to correct this to meet code? These joists are in excellent condition otherwise. Someone drilled through them years ago to run cable through. There are other holes above 2 inches on other joists.

  • 1
    replace them or get an engineer to spec a fix. metal plates or straps would probably be easiest. Commented May 27, 2013 at 8:38
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    The bottom of a joist is, under normal loading, in tension. You should be able to repair it with a steel plate bridging the area with a hole in it. However, you're going to need professional advice. It's not explicitly to code, so you'll need an engineer to sign off on the fix. Commented May 27, 2013 at 13:18
  • Simpson have metal elements that would slp over that. Normally used for studs (so vertical) but probably would work for this application. Alternatively you could fasten a steel strap across the bottom edge to reist tension stress. Commented Feb 8 at 20:21

3 Answers 3


Replacing them? Getting an engineer? For a 1/2 hole in at least 8in joist? Seriously? I mean I'm sure the joist has lost some percentage of its strength. Like pretty small percentage. I would speculate that the lost strength is within tolerance limits for wood, which is not uniformly perfect. Unless you plan on having sumo wrestlers fight on top of those joists, I would just let them be....


As Vitaliy points out, replacing the joists is completely unnecessary, however, I did look into it and came across this article: http://ifbholz.ethz.ch/natureofwood/pc/st/st5.html

Knots and holes do affect the strength of a joist but the three most important factors are: the dimensions of the lumber, the location of the hole, and the size of the hole. Best-case scenario is that you have a hole just big enough for the purpose needed, directly in the center of the joist. Worst-case scenario is that you have a hole that is too large and is located at the bottom of the beam (the tension face). As the article points out, a 1/2 inch hole in the tension face of a 2x10 joist can reduce the bending strength of the joist by as much as 9 percent!


Those holes are effectively notches. If they're in the middle third of the span, then the notches are out of conformance with the IRC. If they're outside the middle third of the span, then the maximum notch depth is 1/6 times the joist's depth for IRC conformance.

To repair them, you should look for notch repair kits, not hole repair kits. Alternatively you can remove the cable, sister the joists, drill conformant holes for the cable, and reinstall the cable. The specification for allowable holes and notches can be found under IRC R502.8. Note that the following section (R502.8.1) prescribes some constraints that aren't shown in the images, so be sure to read the fine print.

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