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Q: When installing french doors on the patio of a house with a slab foundation, how do you support the 3/4" threshold overhang?

I currently have a sliding patio door. The threshold of this door is only 3 7/8" total. This causes it to line up flush with the foundation on the exterior. However, the new french doors I'm replacing it with has a threshold of 4 5/8". So, now when I install this, the threshold will overhang the slab by 3/4". Is this ok? Does it need to be supported? I would like to do this in a way that looks professional.

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  • A: Thoughts



    It can work as-is... but I'd suggest adding a piece of Azek (or equivalent) fascia under the lip of the door to finish this area off, and to provide just a bit of support for this lip.

    Also, make sure it's well-sealed, both around & under the door, as well as around & behind the fascia.

    Best wishes!
    ~Matt

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  • A: Adapter



    Most manufacturers offer a sill support accessory. 3/4" isn't too much to stick out past.

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    May 8, 2021

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