We are ready to pour concrete into a 54"x30" form; our son dug down about
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The slab probably won't move if the earth is well tamped down, but any sulphates present in the earth could affect the concrete and may cause problems with the concrete.
If you don't want to lay a good, clean hardcore to reduce the depth, then you could lay a plastic DPM (damp proof membrane) on top of the earth before laying the concrete - and this will prevent any future sulphates problem.
Cash
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