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Community and Q&A

Why do monolithic slabs have sloped footers?

rgriggs | Posted in General Questions on

Hello. I am attempting to design a monolithic slab for a garage/house project. I have researched monolithic slabs and this is the direction I want to go. But the question is: why, in every drawing and implementation of a monolithic slab, is the inner wall of the footer sloped toward the middle of the slab? Why not just a straight footer? Does this have to do with stress cracks and a better joint between footer and slab, or does it save concrete, etc? Thanks for any info!

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Replies

  1. Expert Member
    MALCOLM TAYLOR | | #1

    Ryan, the joint between the slab and the footings is subject to shear forces and the angled interior face is an attempt to mitigate them. More important than the shape is the placement of reinforcing at the joint. Probably worth getting your engineer to design that intersection if you want to avoid problems.

  2. GBA Editor
    Martin Holladay | | #2

    Ryan,
    It's also easier to excavate soil (or place crushed stone) with a slope at that spot than a right angle.

  3. rgriggs | | #3

    Thank you for your answers.

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