On the far corner of our carport, I replaced an eave-mounted light a few days ago that had no junction box holding it. In trying to be a responsible DIY-er, I decided to go ahead and install a junction box for the new light fixture before mounting it.

I stupidly chose to use a reciprocating saw to try to cut a round hole for the new box. In doing so, I slashed through a joist above the eave, not once but twice. The cut went all the way through horizontally but did not actually remove any chunks of wood material. My concern is that the joist/rafter could be supporting weight that will cause the joist to bow downward, on the side of the cuts.

The two cuts appear to be about the equivalent of notching the joist ~30% of the way up. The joists are, I believe, 2x8's. House was built in the 70's.

Is this something I need to repair, and if so, what is the best way to go about repairing it?

Edit: pictures detailing the boo boo. The cut is just to the right of the new light fixture. I have already patched the eave where I cut the half circle (including the two cuts that went through to the joist) so I'm not going to undo that to take a picture, but at least you get an overview.

I'm honestly not certain that it wasn't a rafter I cut through but I can investigate more when I get time and daylight.


cuts to the right of fixture

closed as unclear what you're asking by isherwood, Tester101 Jan 3 '17 at 19:10

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    Pictures would be helpful, particularly if you are not clear on what's a joist, what's a rafter (or dod you manage to cut through both?) You can like repair with plywood on both sides, glue and screws (basically making a splice there) but it would be helpful to see it. – Ecnerwal Jan 3 '17 at 18:33
  • Are these cuts inside or outside of the wall supporting the carport? Does the carport have a pitched roof or is it a flat roof? See diy.sndimg.com/content/dam/images/diy/fullset/2011/11/7/0/… – Jim Stewart Jan 3 '17 at 20:06
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    There are no "joists" directly above the light fixture (joists terminated above the wrought iron post; before reaching the area of the light fixture). You probably cut one of the rafter tails which support the eave and fascia board. I wouldn't worry about it...just don't make a habit of it. – James Olson Jan 5 '17 at 18:58

Without pictures it's hard to say. I don't fool around with structural (the cost of getting it wrong is too high) I'm going to assume you need to repair it.

What you'll want to do is called sistering. Basically, you'll take a new board the same size as the rafter (you said it was a 2x8 so get a 2x8) and use it to patch the damaged board. You'll need some 3"(or longer) nails or screws. I would also suggest some construction adhesive for added strength.

  1. Attach the new board to the top part. Put the adhesive on and then attach it via nails/screws. Alternate locations and which side you're going from
  2. Glue and nail/screw attach the lower (presumably smaller) part. This may take some clamping. Ensure it's as straight as you can make it.

Once dry, your joist should be as good as new

  • I keep West System epoxy in stock for just such jobs, the stuff is impervious to water once cured, and will outlive the wood. Clamps are fine but I also like to use deck screws, and I like to predrill them. No fan of nails. Make sure the deck screw threads are not engaging in the piece of wood nearest the head; that will hold the wood apart rather than clamping it together. – Harper Jan 3 '17 at 19:17
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    If the joist is not accessible from above or from below without removing soffit, a metal strap screwed to the bottom of the joist might do the job. The bottom of the joist is in tension and a flexible metal strap would supply tension. If the two slashes are 4 inches apart, then a 12 inch strap could be slipped in between the soffit and the joist and screwed through the soffit every 2 inches. – Jim Stewart Jan 3 '17 at 19:50
  • @Machavity, Pictures added now. – trpt4him Jan 5 '17 at 13:25
  • @trpt4him Is the only hole in that bottom beam? – Machavity Jan 5 '17 at 13:30
  • That's the only hole, but there are two cuts also. I was in a bit of a hurry and had to take mediocre pictures from my car. But at least you get a sense of the location. – trpt4him Jan 7 '17 at 3:12

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