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Community and Q&A

Odd rim joist situation

DrJimesTooperMD | Posted in General Questions on

I apologize if this is the wrong venue for this question. I am running into a weird situation with my 1942 house and trying to replace and rebuild a deck. The original deck was a noncompliant horror show that I’m surprised never fell down. I have since torn it down, but am running into issues with rebuilding a safe, code-compliant deck.

The foundation / joist setup for my home is very weird. I have a concrete foundation, and then a 6″x6″ beam that sits on top of the concrete foundation. On top of that 6×6 beam sits the 2×8 floor joists. The floor joists extend completely on top and to the outside edge of the 6×6. There is currently a 1×8 “rim joist” of sorts, which is nailed to the ends of the joists. This 1×8 “rim joist” doesn’t support any load above it and is unsupported from below, since it extends past the foundation wall and what not by its entire 3/4″ thickness.

The previous owner’s solution was to just run about 8 lag screws through the ledger board into the 6×6 beam, for the entire 30′ worth of ledger, yikes.

What are the implications, or any issues with removing the existing 1×8 “rim joist” and attaching a 2×12 in its place, and then attaching a 2×10 treated board to the new rim joist as the deck ledger? As with the existing 1×8 that I would be removing, the new 2×12 rim joist would carry no load above it, but also would not be supported below it by the foundation. I would connect the new 2×12 rim joist to the 6×6 beam as well as the ends of the joists with FastenMaster 4.5″ HeadLok structural screws. The 2×10 deck ledger would then be connected to the 2×12 rim joist with FastenMaster LedgerLok 3.625″ structural screws. Or do I simply flash and attach the 2×10 deck ledger directly to the ends of the joists and the 6×6 beam, forgoing any sort of rim joist?

Here is a picture of what I am currently looking at (the attachment function is not working for me at the moment for some reason):

The 1×8 “rim joist” has already been removed in this picture, exposing the joist bays as seen in the picture. The 6×6 beam was badly rotted from the previous owner’s nonexistent flashing job, so the different-colored pieces you see in the picture are repair pieces that have been tied together.

I hope the picture helpfully portrays what I am trying to describe. Thank you!

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  1. Expert Member
    PETER G ENGLE PE | | #1

    I answered your question on the other thread you posted. in short, I prefer to support decks independently from the house with posts down to the footings when there is any weirdness with the rim joist. Aside from the structural support issues, it eliminates the difficulty of properly flashing/sealing the fastener holes, ledgers, etc. That said, you could probably flash the wall and fasten the ledger straight to the 6x6 sill beam if you wanted to. It's just hard to keep all of those bolts from leaking.

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