Can someone explain how footings keep an outdoor slab from heaving? i understand why they work on an interior slab, but an exterior slab still gets frozen dirt underneath most of it. Same with post and beam footings. Most of the footing is only a little underground and well above the frost line.
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I've stumped everyone?
DO footings keep a slab from heaving? Or do they keep it in one piece as it heaves?
I think footings on an outdoor slab are pretty much useless useless. They can possibly prevent lateral movement, serving as an anchor.
Mark
I'm no concrete guy, but.
A slab with rod, turned down into a stem wall/footing below frost depth should if area around is drained properly-move as a unit or in this case-not move up/down/laterally.
Stem wall/footing with a free slab inside with rod (again, if drained properly) should float as a unit.
All on undisturbed ground or properly compacted fill.
no?
Well, you know I'n no concrete expert either. A footing below frost depth should not heave. A slab outdoors, properly drained, in a very cold climate may heave anyway, due to the frost depth. So a floating slab inside a foundation could move without problems, but a slab with a solid connection to a stem wall may crack from heaving when restricted by the footing. This is just my conception of reality.
With rod turned down into the stem wall........
I don't know and can't think of one I can point to that will confirm or deny. I'm thinking of a reinforced concrete lid with sides down to the footing. If no moisture to expand upon freezing inside that cap, what could heave (assuming compacted stone fill inside and proper drainage.
Screw it, I'm going outside. Yet another gorgious day!