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Flashing ledger board on an existing deck

tech_bones | Posted in Construction Techniques on January 17, 2012 07:20am

The ledger board of my deck has no flashing and is installed directly over top the aluminum siding. The deck boards run perpendicular to the house at a 45 degree angle. I’ve been having some water penetration issues in the wall beneath the deck and I want to retrofit this deck with flashing. I was wondering if any one had any kind of advice for tackling this project.

From reading up on the subject what I believe I have to do is pull up the deck boards to get at the ledger. Then I’ll have to cut into the siding so I can slip flashing behind it, but I’m not sure how much to cut out. Any suggestions? I’m guessing just enough to get  the flashing up behind it, but not so much that it is higher than the deck boards will be. Then I’ll need to re-attach the deck boards, but because the deck boards run at an angle to the house, they’ll need to be nailed into the ledger board and that will puncture the flashing. Should I be worried about that?

Is there anything I missed? It seems like a straightforward job, just a lot of work with pulling up the deck boards.

Thanks!

-John

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  1. calvin | Jan 17, 2012 08:02pm | #1

    John

    You recognize the problem with lapping over the ledger and probably poking a bunch of holes in it.

    To keep from this, I add blocking out away from the ledger (if joists run with the wall-add another joist) a bit-enough for water to pass (and leaves etc) and fasten the decking to that-no puncture.

  2. calvin | Jan 18, 2012 08:51am | #2

    tech

    I use the joist cutoffs for blocks, and the same size joist material if my joists ran parallel to the ledger.

    I seldom do retrofits.  You need enough removed to be able to get that flashing well up behind the siding and felt paper (I'd say 4" min).  You'll need to add something to the bottom of the siding so it just doesn't flop around, you've lost connection to the other siding.  A starter strip won't work, perhaps what's called an undersill trim.  This slips over a cut edge and stiffens it.You won't be able to fasten it, add bead of geocel to the lip that goes up back of the siding.  That might hold it on so someone doesn't convince it to pull off.

    Also, there are flexible flashings available-peel and stick.  If you can cut the siding, remove that run from the connection, it would be easy to both apply the flexible flashing as well as lay in metal.  Depending on the exposure, you might be able to just lift it enough to work behind it.  The flex. flashing will also divorce your aluminum siding (and flashing I presume) from the caustic nature of your treated frame and decking (if treated).  The added benefit to the flexible peel and stick-it seals around penetrations through it.

    Now your stuck with renailing the siding pc you removed and rehooking the course above.

    It really is a suck job and a shame it wasn't done right in the first place.  I hate these kind of jobs. 

    Now, back to the frame.  Water intrusion MIGHT be stopped by over flashing the ledger.  However, all the penetrations they made to fasten through the siding will still be there.  How IS the connection to the house?  Through alum. siding, then through perhaps insulated sheathing is quite a depth of non holding power.  Is the band lagged to the house and where-band joist/ends of house joists?  Through bolted, lagged or nailed?

    1. tech_bones | Jan 18, 2012 09:22am | #3

      The joists run perpendicular to the ledger.

      As for the connection to the house, the ledger has lag bolts that go through the aluminum siding and then a layer of thermo-ply sheathing and then into the framing of the house. I can't really do anything about this though without dismantling the deck. There is no felt paper or house wrap as far as I can tell.

      Here are a few pictures of the deck I took last night if you are interested. http://imgur.com/a/heCGN

      1. calvin | Jan 18, 2012 12:24pm | #4

        Thank for the pictures

        They certainly spared no expense for the hangers.

        And you can see what I mean about the effect that treated wood has on metal-while the bolts may be ok, the washers are corroding.

        It's not going to be easy, but if you can remove and flash, that would be the way to go.  I don't suppose the first lap up from the deck is the bottom of a pc of siding?

        1. tech_bones | Jan 18, 2012 12:55pm | #5

          Unfortunately it isn't. The first lap is the middle of a piece.  I have a fair understanding of what exactly I need to do now. Thanks for your help.

          1. calvin | Jan 18, 2012 04:55pm | #6

            Best of luck!

            glad it's you and not me.

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