How many inches of gravel bed go under a foundation footing?
Question:It's going to be 5'X7' solid not just perimiter, two layer thick cinder block cemented/rebarred together to hold a tub. How deep should the gravel base be? Thank-you!
Answers:
Gravel does not go under footings, only slabs. It sounds like you are pouring a slab on grade with a thickened edge for a footing. Place 4" gravel under the slab and leave the perimeter footings undisturbed soil.
it depends on the soil, most times you can just pour the footing on undisturbed soil, free of organic material. i would either hire an engineer, or talk with the local building inspector, and see what your local ordinances require. you are pulling a permit for this project, aren't you? and what about drainage from this slab foundation? do you live where freezing could blow the foundation apart if this is below grade? just a few thoughts for you to consider, good luck.
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