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I have a problem with about 8 joists in my house. I have had several contractors in for estimates to fix the problem. There are estimates go from 3.5K to 16K. They seem to have different views on what should be done. For more information about my problem, you can look here: More Information

One contractor recommended that I replace all the bad joists at a cost of $2000 per joist. He claims that replacing is better than sistering it. He also claims that it sistering it may not be consistent with code. I believe he is wrong about that. From what I have read, it is my understanding that sistering it is standard procedure in these cases and there is no real benefit to remove and replace. Is there a reason that remove and replace is better?

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    Your reference only shows 1 cracked joist that 2 pieces of 3/4" plywood, construction glue and screws will fix, including the squeak if done right, AND if the crack is the cause of the squeak. But your question refers to 8 total, are these simply cracks here and there. that may not require sistering either or are they rotted?
    – Jack
    Commented Oct 22, 2022 at 3:38
  • They are not rotted. They are cracked. You may need to scroll up to see the original post.
    – Bob
    Commented Oct 22, 2022 at 3:43
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    I would think joist replacement could cause other problems since you would be jacking the house up and down, sawing, yanking, pounding...and if plumbing and electrical stuff is going through the joists...even more disruption. Commented Oct 22, 2022 at 4:54
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    Any contractor that tells you that sistering joists isn’t “consistent with code” is either ignorant or knowingly lying. The building code doesn’t concern itself with such matters, it is up to a structural engineer to evaluate the structure of a house and design a repair if necessary. The “code” will defer to the engineer’s expert recommendation. Not some jerk’s horseshit. Commented Oct 22, 2022 at 6:48
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    "...is joist replacement better than sistering?" To answer that question requires the definition of "Better" The majority of answers here make that definition to be "most common method." Take the advice given here. There is no need to delve deeper into something that decades of experience has answered for you.
    – RMDman
    Commented Oct 22, 2022 at 13:50

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To answer the question, is replacement better than sistering, my answer would be yes, but only if all the floor is removed down to the bare joists. If the house is "platform framed", that possibility has its own problems. If it is a much older home and is "balloon framed" then it is much simpler after all the floor is gone. Yours appears to be platform framed.

To replace a joist while keeping the floor intact would mean finding a way to refasten the subfloor and the finish floor back down to the new joists. This is difficult at the minimum, if not impossible to do it neatly. It would potentially mean running fasteners through any finish floor and into the new joists. Sounds pretty ugly to me....

Sistering, on the other hand allows all the original fastening to remain intact in the original framing and the added joist beside the original is used to reinforce the weaker original. Even when the new sistered joist is added, construction adhesive can be added on top of the new joist to "bed" the original subfloor to the new joist and potentially cure some squeaks.

In my opinion, sistering is a practical way to repair rotted joist ends. In your case, without seeing the other 7 joists, my guess the cracks are from shrinkage that has occurred a while back. I guess there is a possibility that somehow something may have damaged them just recently, but if the cracks are from that type of damage you should have heard or felt something making that happen. Just a guess on my part.

I will reaffirm what I think is the case. Any long splits or even the one you have pictured in the other post does not need sistering, just an added layers of plywood with glue and screws to tie it all back together again, Even the plywood can have some glue added to the tops to tie the subfloor to the new material to hopefully stop the squeaks. It should if it is the subfloor squeaking. If it is the finish floor moving over the subfloor, it will not stop the squeaks. Properly sized screws ran in from below will, or should fix that.

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  • The house was framed when it was built 60 years ago. Since that time, no structual work was done.
    – Bob
    Commented Oct 22, 2022 at 9:45
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Joist replacement should only need to be done if the joist is rotting away for most of its length. If just a small section is rotted, then just a removal of that section(with proper supports) and sistering should work.

Joists also should be replaced if some idiot used half size joists for the span, but then you have a bigger problem.

Most other damage that weakens a joist can be fixed by sistering with equal size joist or plywood patches.

Most horizontal cracks are common and not something to be concerned with, unless quite long and separating the joist in two pieces.

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