Chicago (Suburban) - Concrete Contractors

The footer picture above is for the wall, you would want thee footer under the slab you are pouring , not really needed if you have the proper compacted subbase , and 15Mil vapor barrier , or a layer or sand , really depends on your soil conditions and how well the native soil drains , stable base , proper expansion joints and the correct concrete blend is the key to getting the correct results

 

Way over kill for a garage.