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Today I found some deck joists are either cracked or completely out of shape. I was wondering do I have to remove all the boards to replace these joists?

There are two joists that seem to be really bad (picture 1 and 2 is for the worst one, picture 3 is 2nd worst). There are couple other joists that are cracked like in picture 4. I can get underneath the deck easily.

Any suggestion on what will be the easiest way to get them fixed?

I am new to deck, appreciate any help!

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I've replace a few on decks and never had to remove all the planks because there was enough room underneath to get to the joist hangers. You should remove the screws from the planks going into a joist you want to replace. Then support the joist and remove the hanger from one end and the screws from the other hanger into the joist. Then lower and remove the joist. Take the new joist, work it into the one hanger and the install a new hanger at the other end. You might have to use new hangers at each end if the new joist in a slightly different size than the old one. Then re screw the planks into the new joist.

If you don't have the clearance under the deck to do the above, then you'll have to remove the planks to get to the joists.

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  • I agree if you have the room that is the best way for the one that is bowed I would probably sister the other one lengthwise splits are not as bad as the first photo that being on the end and sagging or bowed pulling the screws and working a new one would be needed. With composite if you do it on a warm day the sag is easily reversed.
    – Ed Beal
    Oct 24, 2020 at 20:21
  • Respectfully disagree with the idea of sistering. The pictured joists are just standing sawdust, and messing around with double joist hangers (especially with one half so compromised) is a pain. Plus, you'd get an extra line of screws in the decking, which would be unattractive.
    – Aloysius Defenestrate
    Oct 24, 2020 at 22:38
  • Appreciate the suggestions! I have a walkout basement, so maybe there is too much rooms under the deck. The joist is about 8 - 9 feet above the ground. I guess the worst case is I remove both hangers and install two new ones. To find support for joist may be a bit tough while I am working on it as the joist is pretty high above the ground... I have another question. The joist is secured by 4 nails (not screws) to the plank. If I need to replace them with screws, what size should I use? And what would be the easiest way to get the nails out?
    – John Xu
    Oct 25, 2020 at 0:10
  • @JohnXu I'd be using 1 1/4" galvanized lag bolts to fit the joist hangers. You'll need pry bar or crow bar to get those nails out unless you just grind off the heads. Supporting the joist would be more important if you were in a confined area., which you're not.
    – JACK
    Oct 25, 2020 at 0:42
  • Got it! Thanks fo much!
    – John Xu
    Oct 25, 2020 at 20:30

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