how to cross existing footing with new footing

Hello, any advice on this is much appreciated...thanks in advance.
Plans for an addition to my home, include crossing an existing stem wall concrete footing with a new footing near one corner of the existing structure. I suppose this is to "tie" the new structure with the old as well as provide a stronger footing support for the new second story which is over this part of the addition. My question is, does the new footing simply butt up to the old footing on either side, or do I need to remove or channel the old footing to allow the new footing to cross? I hope that is clear to understand. Other parts of the footing plans call for underpinning the old footings, and also there are several areas where large pads of concrete will be underpinning the new footings as well. I think this footing design is a bit "over" engineered, but maybe its because there are no steel beams used on this 2nd story addition.
-diytequila
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This doesn't sound like over engineering to me. I'm a bit confused by your problem, but the need to underpin an existing foundation can be considerable if the addition is two stories high. Also, one serious problem to consider is the need to tie the foundations together such that cracks don't appear in the drywall later as the new vs old foundations settle. I have that problem on an addition added years ago to my house. Both foundations are quite adequate, but we have a seasonally recurring drywall crack, inspite of fact that no crack appears in the exterior stucco. The expansive adobe soils on our area expand as they dry during summer. In a current project, I had to add three 3' cubed concrete and rebar footings for posts to very large support beams over a garage space. Originally, the new garage roof with room in truss design created by the truss company put a very heavy calculated "point load" on parts of the existing footing, according to the engineer at the planning department who said was it too much for my existing foundation that otherwise quite large as it met code for convention second story construction. So, I had to hire an engineer to develop a plan that spread the load out. So, the result was cutting the garage floor, digging big holes, and then filling them with rebar and concrete. It was a hassle, and the engineer seemed to take forever, but I don't want cracks in the foundation or uneven settling that could put the garage door frames out of square--a common problem with old houses in our neighborhood. I also want solid seismic stability since we live in California.
diytequila wrote:

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Why not ask the designer for clarification?
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MichaelB
www.michaelbulatovich.ca
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In a previous post Michael Bulatovich wrote...

Exactly my response.
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Bob Morrison, PE, SE
R L Morrison Engineering Co
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