New double garage / workshop

Double garage with a shared driveway. As said, the hobby/workshop room should be about 20 sqm.

So 60 sqm? Or should the double garage of 20 sqm serve as a workshop? Sorry, but it's hard to read, it can mean either.

Oh sorry, I thought it was clearly stated. Double garage+workshop of about 20 sqm

...and how big do you want your double garage to be? There are designs that are larger than the house from the base plate.

I think the garage 30-35 sqm?

Ok, I would contact a precast concrete garage manufacturer: double garage plus adjacent/ rear room. They also have structural engineering templates for the building permit submission. I would budget 45000, including foundation, permit, and some insulation for the workshop.

Thank you very much, that gives me a rough idea.