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Context: I would like to add a flashing pan under my new stacking widows/door. Door width is 10ft. Flashing pan is Z shape 2 in x 8 3/4in x 3/4 in. Ideally 12 ft. long so that it can be bent up the rough frame posts.

Problem: I cannot find a local supplier who would bend a 12 ft long sheet of metal to build a pan. Or perhaps I don't who to contact.

Questions:

  1. Is it ok to use multiple sheets as opposed to one single continuous sheet such that there is one 10ft between the posts, and two 2x2ft at each corner going up the posts? Overlapping by 2ft the 10 ft horizontal sill pan.
  2. Should the overlapping corners two 2x2ft be overlapping on top or below the horizontal sill pan?

Illustration:

Illustration Flashing Pan

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Think like water. Imagine you have a pool in the bottom of the pan 10 years from now. Is the caulking you dutifully applied at the joint going to hold? I don’t know.

I get pans from hvac guys and rain gutter suppliers. (You might have a slightly hard time finding one of them to work for you, but keep trying and have cash in your pocket when asking.) They should be soldering the corners anyway, so soldering a joint in the middle isn’t too much of a leap.

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  • Thank you @Aloysius Defenestrate! I have thought about soldering, but that introduces two challenges. 1 - impossible on Aluminum so I have to go with Steel, and 2 - soldering will introduce a bump in the midspan of the sill which is not recommended for the window. That said, i could try.
    – Max
    Commented Jan 6, 2023 at 20:53
  • Rain gutter companies might be great here. They usually have flat metal on a giant spool and they form it by forcing it through shaped rollers. They should be able to make your flashing in any length you desire
    – Matthew
    Commented Feb 5, 2023 at 23:28
  • Apologies for being late to the comment above, but a bump in the middle just means that you shim across the entire bottom to clear the bump. Commented Feb 6, 2023 at 0:24

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