[fkim119]

I developed commercial property, and built homes.

To do it the right way, you just can't simply add the extra length you need if the foundation is poured. I am assuming you are on a post tension slab. To add the length you need the right way (this is a guess since I don't know your home elevation or floorplan)you have to dowel in to your post tension slab/foundation from the front of your garage. If you simple make cuts all over your foundation, you will be cutting the rebars that is laid into your foundation. Not good. In case of severe weather, the homes foundation will be considerably weaker. In the long run, the foundation will crack. Matter of time.

I would move onto a different lot, make them pour the foundation to the correct foot print and start the right way instead of making something wrong, right .