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There's a post (layman's term) in the middle of my attic that is cracking and bent. It wasn't like that the last time I checked maybe 2 months ago. This is in a 30 year-old house.

Now that I think of it... it may have showed minor signs of cracking 2 months ago but it wasn't noticeably bent. There was a little "feathering" of wood. Barely visible. Now it's looking much worse.

No, I don't see any sign of water damage and there haven't been any snows. Also no big storms lately. I live in Southern Florida.

My idea is to just put a steel plate with a bunch of nail holes in it to try and straighten things out. Or?

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  • Have you had an unusually large snow event, or other plausible cause for the damage in the past two months? – Ecnerwal Jan 17 at 4:16
  • It looks like a 2x4 under stress. It would be strange if it was intended to be weight bearing. – HoneyDo Jan 17 at 4:28
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    I’d first want to know if there’s been any kind of load on the roof (snow?) that would potentially cause this. Or is there a leak that’s allowing this member to become soaked and warp as it dries? After that, I’d sister it on both sides with 2x4s the whole length and use structural screws on both sides that are long enough to penetrate all three boards. Every 6-8 inches or so. – daneb Jan 17 at 4:45
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    Pictures helped a lot.OK, so what you have IS a trussed roof. That 2x4 that's cracked is under compression, as are all the other similarly located 2x4s - those that are perfectly vertical. That tells me that 1) the 2x4 was damaged from the start or 2) there are higher loads on that than what the truss was designed for. It could be the latter but it's hard to tell from the pictures what additional load the side roof might be applying to the truss that's damaged. I would sister that damaged 2x4 with two more 2x4's, one on each side of the damage 2x4, glued/nailed/screwed to the existing 2x4. – SteveSh Jan 17 at 17:44
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    That short section of the roof that's perpendicular to the main roof, and seems to tie in just where the failed truss member is located - was that part of the roof always there, or was it added as part of an addition? I'm poking at whether there are unanticipated loads on that last truss that would cause the buckling you have. – SteveSh Jan 19 at 18:18
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That vertical member is a truss chord not a post. It’s in compression (as @SteveSh) has identified.

It’s buckling due to an excessive vertical load (and probably because of a small defect in the wood).

This phenomenon is identified in Euler’s Formula. While I don’t understand the formula, the concept we know it by is the “slenderness ratio”. That is to say, a short board can support more load than a long board before it buckles, given the same size, material, etc. Likewise, the member will buckle in the narrow direction.

The center chords are the longest member in the trusses AND are in compression. This particular member has a small defect near the middle of the span (top to bottom). It also happens to be at the hip in the roof, so it’s probably carrying a slightly larger load than the adjacent trusses. (We often see defects in chords that cause them to fail.)

I’d repair the chord by sandwiching it between similar size members, much like what daneb described.

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  • Excellent, i learned something. Maybe explain (add to you answer) what type of fasteners to use for the sandwich. Lags, Carriage bolts, Etc. Hold the pickles. – Alaska Man Jan 17 at 21:04
  • @AlaskaMan Because one member is enough (and it’s just the defect in the wood near the middle of the span that caused the problem) three members truly becomes overkill. I like to go back to the truss manufacturer, but if not known or available, then I like screws rather than nails because diy-ers use hammers not guns and the hammering is not good for the joints. I think almost any screw that penetrates all 3 members and spaced 8-12” oc staggered will work. Remember, the skinny direction is now the opposite direction. – Lee Sam Jan 17 at 23:09
  • How long should the 2x4s I'm adding on be? Maybe 2 feet long each? – HenryM Jan 20 at 16:57
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    I’d use a 6’ board and go 3’ past knot. Stagger all fasteners each side. Do not let them align from side to side. – Lee Sam Jan 20 at 17:22

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