We currently have a short basement (5 1/2 height) and are talking to a contractor, architect and structural engineer about digging it out and underpinning the foundation. The foundation is a 100 year old rubble stone foundation on top of clay soil. We are also having a 10 foot section of the foundation replaced so we can reduce the width of the foundation wall from 18 inches to 8 inches to make way for a staircase. Does anyone have suggestions of things to watch out for during this project? Have you had this work done or done it yourself and there were problems that popped up during or after construction? Leaks between new and old foundation? Mistakes made during construction?