Looking at your other post, it looks like you have a lot more than steel VS concrete going on. If the old foundation was built on dirt that you are removing, that is not good. First thing is to make sure to shore up any areas that you are modifying.
Due to the fact that you are risking the loss of your house completely you will definitely need to talk to an engineer and figure out how to hold your house in the air after you remove it's support. Look at it this way, it may cost you a few thousand dollars to have an engineer help you, or it could cost you your house, your possessions hopefully that is all if you do not support it correctly.
Ex Realtor, house flipper, remodelor and now building a vintage truck, making friends and fixing my house.
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