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Hi, Richard. Welcome back to Just Answer.
Hmmmm.... Only 9" !! Sounds like a kit to me. Probably printed outside the USA.
Standard code here in the USA requires minimum 12" into natural undisturbed soil. In other words if there is any fill dirt you must dig down past that by at least 1 foot.
Of course you could always compact any fill dirt and have a soils engineer certify the compaction too. That runs about $700.00 to $1100.00 just for the soils engineers scribble on the plans.
As for the width you only have to have enough room to put a 2x4 on top for a sill plate, but that is only for the first 3-1/2" or the height of the form board. after that the tractor operator that digs the footing is going to use a 12" bucket so the footings will be 1'x1' at least.
There is no problem going bigger with the footings, but 1' is plenty unless there is a very heavy wall that is going to rest on them. You would need to have that engineered though. This is usually for multiple stories only.
Industry standard for rebar in footings is one up and one down. Minimum 3" clearence between the edge of the concrete, and any rebar to soil. That said the answer to the stabing the rebar into soil answer is a definate no. The steel not only rusts out but in the process expands causing, at minimum, major cracks and eventually complete and/or catastrophic failure of the concrete .
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