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I noticed several joists sit < 1/2 inch on the sill plate. Is it dangerous? What should I do to enforce them. enter image description here

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  • It might be enough, but it seems you have an inch or two of cement/block wall to add more wood. It also looks like the joist is sinking a bit into the sill plate, so depending how the floor above is, might think of raising the joists(not as important if floor is flat).
    – crip659
    Dec 10, 2023 at 23:05
  • Yes, I have 1 inch spacing from the sill plate to the edge of the cement wall. Should I cut a small piece of wood and put under the joist?
    – movila
    Dec 11, 2023 at 0:05
  • I would use long pieces. I imagine that is not the only joist like that, so eight foot 2x2s should work. A five or ten pound persuasion hammer to fit it in.
    – crip659
    Dec 11, 2023 at 0:14

2 Answers 2

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To correct this either widen the sill plate or install joist hangers.

Replacing the sill plate could be tricky as it will probably be bolted vertically into the CMU foundation. There should be a damp proof layer between the concrete and the wood. If you do decide instead to add wood to the side of the sill plate be sure to put a damp proof layer below it.

Installing joist hangers will require jacking up each joist by the thickness of the metal in the hanger, there's a risk that this may disturb walls and trim on the floor above. if the floor surface above is something inflexible like ceramic tiles I would not be installing joist hangers - too much risk of busting the tiles.

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    There are some styles of joist hanger where the lower strap may be offset enough from the face to allow installation without needing to jack anything up. Might want to shop around and look for those.
    – Ecnerwal
    Dec 10, 2023 at 23:27
  • I found this type of joist hanger at Home Depot homedepot.ca/product/… Would it be enough if I just screw it into the header plate?
    – movila
    Dec 11, 2023 at 0:12
  • Joist hangers (as far as recall, exclusively) mount with joist hanger nails, not screws. Joist hanger nails have superior shear strength compared to screws and "normal" short nails.
    – Ecnerwal
    Dec 11, 2023 at 0:22
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    @Ecnerwal, Simpson tests their connectors for nails and their "SD" screws. Technically the OP could use specifically these screws, strongtie.com/products/fastening-systems/technical-notes/…. Not random construction screws, though.
    – popham
    Dec 11, 2023 at 0:57
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Joists must have 1-1/2" bearing on the sill plate under IRC R506.2. Your joists are therefore deficient.

Fix this with joist hangers. Your image seems to show a 2×10. If that's the case, then get a joist hanger built for 2×10s. The existing toe nails provide some strength, so drive them deeper to clear the connection for the joist hanger. Simpson makes their own nails and screws for their hangers. Use those instead of whatever you have laying around the house.

For nails, you want their 10d 1-1/2" nails for straight nailing and their 10d 3" nails for toe nailing. That's for the typical scenario of a single rim board, though. With the tiny bit of sill plate you have, however, I suspect that you may have a double rim board. In that case you would want nothing but 10d 3" nails.

For screws, you would substitute SD9 1-1/2" screws for the 10d 1-1/2" nails, and you would substitute SD9 2-1/2" screws for the 10d 3" nails. See Simpson's chart to confirm.

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    Pro tip: if you’re using joist hanger nails down there, get a palm nailer of some description. Dec 11, 2023 at 2:48
  • @Aloysius, yeah. I was thinking that the screws might be a better idea with the drain and copper right there. Can't quite tell from the image.
    – popham
    Dec 11, 2023 at 4:25

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