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Community and Q&A

Flashing an exterior base plate

fall50 | Posted in GBA Pro Help on

After searching the site similar to previous questions, I am not quite sure how to proceed.  New LP siding will go up next week, in the meantime I am trying to get some flashing details squared away in terms of best practice.

This is a retrofit situation.  First questions pertains to whether I would use flashing tape which would connect to the sheathing, extend to the concrete slab and rundown the side slab.  Z flashing will be added after the fact regardless, however its unclear if this should be taped first?

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  1. user-2310254 | | #1

    Matt Risinger has a video on Bomber Flashing, which looks like the right product for this situation.

  2. Expert Member
    Akos | | #2

    The sill to foundation connection in most houses is a big source of air leaks. You definitely want to seal this.

    Flashing tape is a good way to go, just check the manufacturer's literature for compatibility as it might need primer for concrete.

    1. fall50 | | #3

      @Akos and Steve

      Thanks for the follow up. I think taping that area looks to be a decent idea. I may be off base but the only drawback I can think of is if water got behind the sheathing, then it would be trapped in the wall cavity, as that exit point would be sealed by tape. Obviously conventional thinking is that's the purpose of the WRB in combination of the of the site made Z flashing , as any water would run down the WRB and onto the Z flashing.

      If gets behind the WRB and starts dripping down the sheathing, it still hits the tape and would not penetrate under the base plate.

      Am I missing anything? Over the tape would be a z-flashing with the wrb draped over the top flange.

      PS Will be throwing up a post later on drip cap and integrating into the WRB for windows.

      1. Expert Member
        Akos | | #4

        If water gets behind your siding and your WRB, you have bigger things to worry about than the base flashing.

        Taping this joint is a standard detail. Just make sure all layers lapped in correct order. Tape, Z flash, WRB.

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