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I'm remodeling my kitchen and pulled up the old flooring down to the joists. I discovered that a hole was drilled down into one of the joists, nearly 3/4 of the entire height of the joist. The joist is a 2x10, spanning 14 feet.

The options I'm considering are:

  • Add a new joist that runs the full length of this joist, glue and nailed to next to the original joist
  • Use a repair plate
  • Add a section of joist (3-4 ft) and connect with glue and lag bolts

What's my best course of action here? Is the full length joist overkill?

side view of joist

  • Where on the 14' span is the hole drilled, like out near a supporting beam/hanger or near the middle? – Jimmy Fix-it Nov 30 '18 at 15:50
  • It’s about 3 feet from the steel I-beam it is resting on – kponz Nov 30 '18 at 15:54
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    Any of those are good options. It comes down to personal preference. I'd do #3. – isherwood Nov 30 '18 at 16:09
  • Other than that hole, is the joist damaged? – FreeMan Nov 30 '18 at 17:39
  • @FreeMan No, otherwise the joist is fine – kponz Nov 30 '18 at 18:46
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There's nothing about that old joist that's really worth trying to restore it to full strength, which would be iffy at best.

I'd sister a second joist right next to it and nail it to the original - no need to glue it. That should be simple, quick, and inexpensive. You'll need to get the new joist in so it rests on the beam or wall that supports it at either end, but that's usually not too difficult.

You could just remove and replace the old joist, but I don't know if that's worth the trouble, the extra joist won't do any harm there.

One possible confound to replacing the joist that came up in the comments: if there is plumbing and / or electrical running through the joist, it may be a lot harder to double up or remove and replace the whole joist.

If it's a lot harder, I would not hesitate to repair the joist, I'd sandwich the joist between two pieces of 3/4" plywood glued and nailed on. I'd want a minimum of 2' on either side of the damaged spot.

If there's not even room to place 4' of plywood, you could add 2x10s on top of 1/2" plywood or OSB and bolt the whole thing together, making a three ply flitch beam in the repair section. (Flitch plates are usually made of metal, but that would be a bit over the top for weak floor joist.)

Keep in mind that one weak joist could cause some sag, may mess up your tile floor, etc., but it isn't going to make the house collapse.

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    I agree, but I'd glue it to the old joist and the subfloor to prevent noise from foot traffic. – isherwood Nov 30 '18 at 16:22
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    The "no-doubt" solution isn't necessarily easy. There could be alot of other stuff going on in the rest of the span - wires, pipes, ductwork hanging from it or penetrating it, bracing, etc. Plus manipulating a 14' 2x10 in likely a confined space may be difficult to impossible. – CoAstroGeek Nov 30 '18 at 20:28
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    I think then, that we're all in agreement that none of us are structural engineers, so we're providing the "CYA" internet-advice answer in the hopes that the OPs house doesn't collapse while secretly believing that calling in an SE is the only way to be sure, but that option really falls into the "nuke it from orbit" realm of overkill, and common sense says a lesser repair will be sufficient. ;) – FreeMan Dec 3 '18 at 13:33
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    @CoAstroGeek - I just saw your answer, you raise a valid point, I am going to edit the answer. – batsplatsterson Dec 3 '18 at 13:46
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    Since I had easy access to the joist from above (no subfloor), the full joist solution worked well for me. I was able to rest the new joist on the I-beam on one end and the sill plate on the other. One interesting note is that the original joists (including the neighboring joists) had a slight sag in them from being over 60 years old, so I ended up using a planer to bring the top level of the joist down to match the existing joists. I agree that in the case where the "no-doubt" solution is infeasible, any reinforcement of the joist would still be preferred. – kponz Dec 5 '18 at 15:59
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I'd go with 2x10 or 3/4" plywood the full height of the joist and 18" to 24" to each side of the damage. Glued & nailed to both sides of the joist. No way do you need to sister or replace the entire span.

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This is a good example of something that repair plates (Flitch plates, not nail plates) are suited to.

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