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How to mount a deck ledger on a Larsen truss wall?

user-1105327 | Posted in General Questions on

We need to mount a 2×8 pressure-treated deck ledger to a conventionally framed wall that has a 8″ larsen truss attached to it.

The frame is as such: 2×10 rim joist bearing upon 2×6 mudsill, 5/8″ T&G OSB, 8″ Larsen truss, 1×4 cross-strap, Tyvek. The deck ledger will be mounted at the same elevation as the rim joist.

The supported length of the deck is not too great, between 5-8′. I would like to attach the ledger on the same plane as th 1×4 strapping and not directly against the OSB.

Does anyone know of a detail for this? i been trying to come up with a detail where the ledger is bolted to the rim joist with long carriage bolts with squash blocks preventing the trusses from getting crushed, but I would need an elegant way of keeping the ledger spaced off the Tyvek to allow for drainage, etc.

We plan on using 1/4″-3/8″ cedar lathe for the rainscreen.

Thanks again, gba.

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  1. GBA Editor
    Martin Holladay | | #1

    I have never been a fan of deck ledgers. (To see the type of rot that can happen when a deck ledger is poorly flashed, check out All About Wall Rot).

    The GBA Encyclopedia recommends against deck ledgers: "The best decks have no ledgers. Ledgers are the most vulnerable part of a deck, and they should be avoided entirely if possible. A free-standing deck with an independent foundation will last longer and cause fewer problems than a deck that is attached to the house with a ledger."

    So why not just install a few more piers, so that your deck has an independent foundation?

  2. user-1105327 | | #2

    i considered having the deck self-supporting but decided against it as i didn't want the footings nearest the house to be both bearing on the perimeter drain and rainwater leaders and above the frost line. i reasoned i could flash it properly as the ledger is quite simple: one staright 16'er. alas, it is -10c outside now...!
    thanks again for your help, martin

  3. GBA Editor
    Martin Holladay | | #3

    If you install a beam parallel to your house, and then cantilever the deck joists over the beam, then the piers closest to the house don't need to bear on the footing drain.

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