How to create a strip foundation?

Hello everyone,

I am currently planning the renovation of my basement... due to planned insulation, etc., I unfortunately have to underpin the existing strip foundation, as it is not deep enough.

Since I will not excavate the house from the outside, I have to carry out the underpinning from the inside.

Hence the question whether anyone has already gained experience with this or which tools you have used for this???

I would like to make this tough job as easy as possible... possibly using a mini excavator, etc.

I am looking forward to your tips...

Thanks a lot in advance
Regards
Achim