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Community and Q&A

Flashing deck ledger

canadianexpy | Posted in Green Building Techniques on

So my build is getting closer to a go this spring, as plans are wrapping up, I’m trying to get the small details correct, I’ve learned on this site, these can come back to bite me if not done correctly.

So our house is single storey with a walk-out basement and full wrap around covered porch.
Walls are 2×4 stud 1/2 sheathing taped, 6″ polyiso(2 x 3″) ,Tyvek, 3/4″ furring with vinyl siding , basement is 8″ ICF(Logix)
so 13.5 ” total width plus 2″x4″ stud walls on the interior.

I’ve attached details with me adding aluminium flashing in RED and in BLUE a peel and stick membrane (blueskin or similar).

Flashing 1 is over is over top the ICF wall.
Flashing 2 is over the walkout stud walls.

So is the detail I added look correct?

Would you use the peel and stick or something else here (BLUE line)?

What depth closed cell spray foam would you recommend against the rim joist?

Dave Zone 6

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  1. GBA Editor
    Martin Holladay | | #1

    I prefer to see an air space between the deck ledger and the rim joist. The two details below (one from Fine Homebuilding, and the other from GBA) illustrate one approach.

    For a discussion of this issue, see What is the proper way to flash a deck ledger?


  2. canadianexpy | | #2

    Thanks Again Martin, not sure how I missed that when searching for details.
    I like the 1/2" space idea ,will be adding that to the plans.

    Just to confirm your comment in the original link you run flat stock down over the sheathing or in my case the rim joist from the above siding to below the ledger.

    Is there a reason not to kick the that flashing out over the ledger? Like shown by my RED line.

  3. JC72 | | #3

    Here's a good link which shows the flashing over the top of the deck ledger.

  4. canadianexpy | | #4

    Thanks John for the link, good info I like the Deck 2 wall spacers.

  5. Expert Member
    ARMANDO COBO | | #5

    We always run the teaped sheathing and taped exterior foam continuosly through the rim joist, then I Install a nailer attached to the framing rim joist with appropriate bolts. The reason is to have good and continuos moisture management and outsulation to minimze thermal bridging at the same time.
    We typically do 1/2"-1" taped outsulation in CZ2-4, but I've done as much as 2", however, you need to have an Engineer verify the attachment.

  6. canadianexpy | | #6

    Thanks Armando

    I looked into attaching the ledger off the wall by the 6",(REMOTE Manual) but would need another Engineer to sign off on this, all my money goes to Engineers!! You guys are great ! but need some money left over to build the house.
    I'm hoping the closed cell spray foam on the inside will be enough, so not be a large energy hit. Still be thermal bridging from floor joist to the inside past the spray foam, but hopefully it's minor.

    Just need to decide right thickness(R-Value) of spray foam for this location.

  7. Expert Member


    Can I suggest one variant on whichever of the many ledger details that have been posted you choose to use:

    Fasten your ledger 3/4" lower than the top of your joists. That way the flashing you run over the ledger isn't sandwiched in between the decking and the ledger. Instead there is a gap for water to drain. And install the flashing before the joists. That way you avoid the awkward situation you see in the Hammer and Hand detail where they can't decide whether it should run behind the joists or over them.

  8. Matt Bath | | #8

    Hey Dave, I am also building a second floor walk out deck and didn't want to pay the engineering for a freestand. I'm planning on beveling the foam and also using the deck spacers. Here's a close up with rainscreen and siding removed for clarity. Malcolm, I like the sound of what you're saying and I see the issue but I couldn't understand your solution based on what you wrote. Quick visual?

  9. Expert Member


    Sorry I didn't see your post. Here is a quick sketch. The ledger being lower than the joists creates a path for water to drain down the flashing, below the decking, and away.

  10. Matt Bath | | #10

    Thank you Malcolm that makes more sense. I was imagining it to be more like Martin's method of draining behind the ledger

  11. Expert Member
    Michael Maines | | #11

    I also don't understand why H+H would space the ledger AND run flashing over the top. I sometimes use Maine Deck Brackets and have used a free-draining 1/2" or 3/4" space, but find Malcolm's detail the easiest to use in most situations--clean, elegant, simple, effective.

  12. user-6504396 | | #12


    Late reply to an old post -- I agree with you. It seems to me that H&H's approach doesn't allow the water to flow through. Our set up is such that our joists will sit on top of the ledger board. It has to do with our SIP floor and the beams below. I am thinking of using the spacing without z-flashing approach as Malcolm's doesn't really apply in our case. We will be using 2 foot concrete pavers as the deck surface and so I will need blocking between the joists at the house. I plan to space those away from the house as well. I was thinking of using vinyl backer flashing over the top of the peel and stick flashing that is there now. Does anyone have any recommendations for a good product or important properties of that type of material?

  13. Expert Member
    MALCOLM TAYLOR | | #13


    Sorry, I don't have any good suggestions for the flashing.

    I have built a couple of decks with concrete pavers.

    It's quite hard to get the joist spacing exact enough for bearing. I ended up strapping the deck with 2"x4"s.

    I also found the bottom of the pavers aren't entirely flat. To stop them rocking it helps if you put a layer of gasket on the strapping for them to sit on.

  14. hughw | | #14

    As to the H&H detail....why flash over the deck ledger? In my opinion, it should sit clear of the siding and waterproof plane with spacers as shown in other detail.

  15. user-6504396 | | #15


    Thanks for the reply. I always appreciate your comments. I was thinking of using these under the blocks, just the 1/8" spacer piece. They have pie shaped shims you can stick in to get the blocks level.

    The system requires sistered 2x joists but my framer recommended just using 4x joists. It's about 15% more in material cost but he said trying to get the PT lumber to line up when sistering is a problem. This is our first time, so any suggestions are welcome.

    What did you do on the stairs? We are planning to use 1 ft wide pavers with the risers coming down on top of the treads (vs. traditional tread running behind tread). We will have to use more than one paver per tread (left to right). We aren't sure how to support them and attach them so they stay put and don't crack. We were planning on using PVC risers as the rest of our exterior trim is PVC.

    We are planning on having the pavers extend over the rim around the edge of the deck and butt the PVC trim to the underside of the pavers. We will be using cable railing and SS hand rails.


    PS I never got the chance to thank you for earlier advice you gave me on bird blocking between my trusses. What the framer was planning would have been so much weaker (and not meet code) vs what we ended up doing. Your comments are what caused me to look into it more. One of these days I might write up what we did. It worked out pretty well and was relatively easy to do.

  16. user-6504396 | | #16


    I agree. What do you use for the waterproof plane? We have Vycor on the wall now but I was hoping to add another layer of flashing between the Vycor and the spacers to protect the Vycor for abuse and UV. I have about 20" of space to cover and was hoping to find something like a 1/16" or 1/8" vinyl material.

  17. Expert Member
    MALCOLM TAYLOR | | #17


    Glad to hear I was of some help. Posting your experience would be very helpful to the rest 0f us.

    Wood decks are maintenance generators. To keep them up requires giving up a precious weekend each summer. Your plan to use pavers, PVC and cable decking makes a lot of sense.

    I did one using spacers, as the pavers were on a membrane roof over a garage. They worked well. I had the same dilemma over the stairs. My solution was to get an aluminum frame made by a local boat builder, which had front and back bars to contain the pavers. That's sort of cheating I guess - and was only possible because they were a short run.

  18. hughw | | #18

    Depending on the siding, we might continue siding all the way down and set the spacers on that....On our own shingled house, we did that 35 years ago, but the spacers we used then were 5/4 pressure treated lumber cut about to size as vertical blocking about 4' o.c. Today, we would probably set a 5/4" board on top of the vycor and run it horizontally the length of the deck with appropriate metal flashing above.

  19. user-6504396 | | #19

    Those stairs look beautiful! Now I have to ask a bunch of questions because I want to reapply aspects of them.

    How did you deal with the open risers? Is that gap less than 4"? Are hand rails not required? Why aluminum vs. SS? Are those custom cast stair treads or are their individual 2 foot pavers contained between the front and back bars? Did you anchor the concrete to the aluminum or just set them in the metal track?

    Thanks for sharing this.

  20. Expert Member
    MALCOLM TAYLOR | | #20


    The 4" and under spacing for guards doesn't apply to stair risers in our code. I don't know if it was ever explicitly referenced in past editions, or just interpreted as applying by inspectors, but it isn't there now, or being interpreted that way any more.

    Handrails are required, and hopefully the owner will install them some day. Last time I was by they were sitting in the corner of his shop almost a decade later.

    Aluminum because that's what they make the boats from. There was no cost difference.

    I cut the pavers down to fit the stair frames. Each tread is made of several pieces.

    The pavers sit in the track on gaskets, which both stop them from creeping, and isolate the aluminum from the concrete.

  21. user-6504396 | | #21

    Malcolm, Great information, thanks again!

  22. Expert Member
    BILL WICHERS | | #22

    Malcolm, if you are using treated lumber that aluminum might be a problem. Some of the treating compounds have a rather severe reaction that will rot aluminum in a relatively short time, especially if the interface area tends to be moist. My dad had this problem where he'd built a short extension to his aluminum frame dock using treated lumber. I had my metal fab guys weld up a transition bracket from stainless steel sheet to avoid the materials compatibility problem.

    The boat guys you used probably have TIG welding experience, so they can probably work with stainless steel too. Stainless steel is a lot more resistance to corrosion than aluminum and the cost isn't much different if the fab shop is buying large enough amounts of the materials to get decent pricing.


    1. Expert Member
      MALCOLM TAYLOR | | #23


      I learned that the hard way after building a long privacy fence out of ACQ lumber and Galvalum panels. The panels first developed long runs of white powder and then rusted out where they were fastened. They all ended up having to be replaced with galvanized.

      A few years ago the lumberyards around here switched to MPS treated wood, which while still copper-based, doesn't corrode aluminium or ordinary fasteners. I sure don't miss ACQ. It didn't last very well either.

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