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Community and Q&A

Parapet Flashing

Joe_Adams | Posted in General Questions on

Hello everyone,

So, I am about to install some new parapet flashing in a new personal retrofit project. 

The contractor has suggested a specific model. However, I find the drip edge to the external side of the building too close to the wall. 

My question is: What is the minimum recommended distance between the drip edge of the flashing and the wall to guarantee that the water drips away from the building?

I acknowledge that this distance may depend on the height of the wall, rainfall or wind, but I wondered if there is any general guidance.

Many thanks in advance,
Joe

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Replies

  1. Jason S. | | #1

    Joe,

    Any dimension greater than say the width of a couple water droplets will offer some benefit of reduced facade staining, which is the main purpose of the drip edge. For many commercial buildings that's all you see. If you have a highly susceptible cladding like natural wood or engineered wood of course more is better but you're never going to totally negate wind driven rain. There are too many microclimate variables to say that X number of inches will protect X number of feet up to X wind speed etc. Only rule of thumb: more is better.

    I read somewhere that a hemmed edge flashing works counter to the water shedding and can encourage water to curl back toward the wall a bit, but I think that's why most stock profiles kick out at 45 degrees for at least 1/4", both for a less sharp leading edge and also for some margin to effectively drip, assuming the flat face is flush with cladding.

  2. Expert Member
    Malcolm Taylor | | #2

    Joe,

    All you can hope for is that the water doesn't run by capillary action directly from the drip-edge back to the wall. As Jason said, for that any dimension bigger than a water droplet works.

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