1 Helpful?

Why do monolithic slabs have sloped footers?

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!

Asked by Ryan Griggs
Posted May 12, 2014 12:09 PM ET

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3 Answers

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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.

Answered by Malcolm Taylor
Posted May 12, 2014 8:31 PM ET

2.

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

Answered by Martin Holladay, GBA Advisor
Posted May 12, 2014 8:37 PM ET

3.

Thank you for your answers.

Answered by Ryan Griggs
Posted May 12, 2014 9:57 PM ET
Edited May 12, 2014 9:57 PM ET.

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