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HI, I would like to talk to anyone who has added a basement room under an existing slab, by sawing an opening in the thin part of the slab and excavating underneath, then added a floor and walls, etc. It seems possible, but some questions I have: is the thin part of the slab strong enough to stand without the support of the soil underneath, or would it have to be reinforced/supported somehow? Will the excavation, even though it would not extend to the slab perimeter footings, disturb the support of the footings enough to cause foundation movement? Seems to me a separate exit to the outside would be needed in the interests of safety (I intend to use the space as storm protectionas well as storage).