Hello,
Has anyone ever poured a monolithic or frost-protected shallow footing under an existing slab?

Reason - Existing garage on a small lot. Not able to lift and move garage. Not enough room to excavate 48" down to pour footings and set blocks.
Looking to connect to the house, but needs to have frost footings.

Garage 22' x24'
Live in central MN
Building official isn't too familiar with this type of footing so I'm trying to get as much info as possible and present it to him.

Thanks!