Crack along floor Joist in crawl space. Another similar on the same joist further down. Major issue or simple fix? Suggestions?

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    I doubt it's 2 inches thick unless your home is more than 80 years old. What am I seeing along the bottom if not a rabbet? Just a dirt line? – isherwood Nov 16 '18 at 14:26
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    "It's the soup of the day." I realize the joist spans the house. How many feet and inches is that? – isherwood Nov 16 '18 at 14:28
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    Also curious about the dirt line to the left... – Aloysius Defenestrate Nov 16 '18 at 14:30
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    I didn't mean the pipe. There's a brownish horizontal line that corresponds with the crack. I initially saw that as a shadow in a rabbet. Now I see that it's just discoloration or maybe the crack itself. – isherwood Nov 16 '18 at 14:40
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    If it's sagging you can just use a jack with a post to carefully lift the joist back to level (make a T-bar to cross several joists and lift until they come to the same plane). You can then sister a joist to one or both sides - drill and lag bolt with big washers and construction adhesive. Job done. From the pictures it doesn't look worth the effort, to be honest. – J... Nov 16 '18 at 16:55

tl;dr It's probably just a localized weakness and not a serious problem.

I suspect that the joist cracked due to 1) the off-color streak we see, which may be heartwood, and 2) the knot. Both are very weak points in the wood that wouldn't normally be a problem, but their unfortunate proximity combined to dramatically weaken the wood.

The outstanding question is whether there's undue stress on that particular joist, causing sag and severe tension on the bottom edge. We can't say much about that through this little hole in the internet.

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    Thanks for feedback! Appreciate it. I will have my handyman check it out next time as well. Just moved into older house so checking off some things I see. We had water in crawl space (same area) this week due to heavy rain. Not standing but just wanted to make sure structure is sound. – Mike C Nov 16 '18 at 14:47

I’m always surprised how people can look at a structural failure and determine that it’s “not a serious problem.” I have to calculate the load to determine if it’s serious. YOU HAVE A FAILURE. Do not ignore it.

A 12’ span is not extreme, but those joist seem extra large for normal construction. If they’re more than 2x12 at 16” o.c., then the designer was trying to do something special.

Is there something special above those joist: like a hot tub, waterbed, etc.? Make sure you follow through and have it checked out. At a minimum I’d fix the support for the pipe. That sagging could put stress on other joints.

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