Statics for the foundation of a wooden garage

Directly next to our single-family house, a custom wooden garage measuring 6 x 9 m is planned, which will be built by a master carpenter. The garage floor is to be paved, i.e., there will be a strip foundation that will reach down to the undisturbed soil at the wall adjoining the basement and otherwise be frost-resistant. The garage itself will be designed by the master carpenter according to snow loads and other requirements, but what about the foundation? Actually, a 40 cm wide strip foundation should be more than sufficient. Can a structural engineer just calculate that like this? If yes, what costs should I roughly expect here? Or the company that is supposed to pour the foundation? Or is there some way to get a standard structural calculation for the foundation of a corresponding prefabricated wooden garage? What approach would you consider the best?