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Community and Q&A

Waterproofing Balcony Deck

ryansheeran | Posted in Green Building Techniques on

I have been asked to frame stairs off a waterproof balcony that is surrounded by walls on three sides. The balcony has a slope of 2% and no gutter details. The water is going to run off from the back wall out over the edge of balcony. I would have built a free draining deck balcony but the people I am working for are stubborn. The wall finish is t1-11 and the deck boards will be 1-1/2″. I have mounted the ledger flush with the drainage plane of the deck. I will mount my stringers a little lower on the ledger. The first riser will be against the ledger.    I plan to use sleepers and a floating deck on the balcony. The next step is metal flashing, I feel like there is a detail I am missing on how the water is running off the deck. How would you waterproof the deck or any flashing details? For the  extended flashing on the walls to the left and right, do i cut a slot in the panel siding for the peel and stick that still has release paper to stick out for drainage. I flashed the ledger using mike guertin’s methods. 


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  1. Expert Member
    Michael Maines | | #1

    It's hard to visualize everything you're describing. Could you provide a sketch? It's ok if it's rough. Drawing it in section would be most helpful.

    1. ryansheeran | | #2

      Hi Michael,
      Here are some sketches. Sorry, I am bad at explaining it.

  2. Expert Member
    Michael Maines | | #3

    Ryan, thanks for the drawings. Please don't take this the wrong way but if you're not sure how to deal with water in this situation, you may want to bring in someone who does. There are too many details that have to be done correctly to convey on a web forum.

  3. user-2310254 | | #4


    Schulter makes a system for waterproofing decks and balconies ( Even if you don't use it, there details may be helpful in solving this challenge.

    FYI. It is really important to have an effective drip edge at the end of the slope. Otherwise, capillary action may pull the water back into the structure.

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