My ideal workshop would have a roll-down steel door (cortina metálica) 3 meters wide and 4 meters tall. Inside, it would be 5 meters wide, 25 meters long, and 5 meters tall. Its walls would be solid brick, shared with neighboring industrial buildings, and its ceiling corrugated galvanized sheet steel, interrupted with the occasional translucent fiberglass panel, supported on welded arch trusses. The floor would be sandy soil, and it would be on a rise or hill some 15 meters above the usual water table. It would have electricity but no water, sewer, gas, telephone, or internet service. The roof would slope down toward the street, and on its front edge, there would be an old sheet metal sign with the name of a former occupant, obscuring the view from the street of the roof. It would have a couple of sheet-metal chimneys.
I would build a meter-thick wall up to the ceiling, some 7 meters inside the front door, separating a 35-m² “front office” from a 85-m² “back office”. I would dig out 500 mm of soil in the front office, grout the soil beneath it to solidify it, and replace it with broken-stone construction aggregate, thus providing a surface on which a delivery van could park safely. The front-office/back-office firewall would extend deeper than the broken-stone aggregate, and considerably deeper than that I would have to grout the soil that supported that wall to keep it from sinking in, because the wall is about 12 tonnes per square meter (120 kPa).
I would insulate under the steel roof with fiberglass batts. In the back office, I would replace 10m² of the steel with translucent fiberglass panels, under which I would install photovoltaic panels, with fiberglass batts beneath them.
The front office would XXX