In my part of the country we go 54" for footings, to get below the frost and they run $36 per linear foot. You have 92 ft ($3312). I put it in high enough out of the ground and poured the slab so the foundation serves as a curb for inside the garage. Water dripping from vehicles don't contact the wood plate or your finish material inside the garage.

The floors I don't know because I paid a guy $200 for a day and he brought all the tools and supervised us, I provided additional help from friends, I bought the concrete.

Garage slab like that would be maybe around $2000 or less, labor and all. You can easily figure $5000 for concrete in a garage then you need to factor in your approach and some codes require a concrete drive all the way out to the street.

My brother bought a $2900 garage kit from ******* and had $10,000 invested when it was done. And done wasn't finished on the inside. That's another whole episode.

In my area, excavation, footer, foundation, grading, fill, slab, and backfill costs for this garage would be about $6000US.

You can typically figure foundation/slab to be about 40% of total garage costs.

Thank you for your response! Here we thought a detached would be relatively inexpensive but are finding out that's not the case.

Thanks again and once this job is completed I'll everyone know what this ended up costing us.

Ken