I envy you owning your own building. I shudder at the thought of what I've spent in building out my leased warehouse space, not to mention the rent over 12 years, although I seriously considered buying last year before proceeding with an expansion plan, and I just couldn't afford it. With the economic changes since then, I know I am fortunate I made that decision.
12-1/2 yrs. ago, I started by renting a warehouse with 750 sq. ft. for $600/month. It had concrete floor, corrugated walls & a 24' ceiling. It had a man door & 12'w x 15'h roll door, next to the 3' man door & one window. Over the next 11 years it gradually evolved to completing a second & a third floor with 7-1/2' ceiling heights. Also gradually, the entire first floor became ultra clean production environment with VCT tiles floors, textured sheetrock walls and ceiling& recessed lighting. The roll door still serves us because we have a sliding glass door looking in on the vinyl production room, giving us more natural lighting & a second way in and out since the steel door is right where the sales counter is often in use. Other than 2 staircases, the second floor covers the entire 750 sq. ft., but the third floor has a 4' x 10' opening above the roll door. This makes a great landing where items can be forklifted up to the second floor, and on occasion we can wrestle items between the second and third floor more easily than the stairs. Over time the second floor has become a fairly clean office environment, while the third floor is all "shop" environment, and a good place to store material, coat out boards, or assemble woodworking etc.
Last year, after years of anticipation, I was able to secure the identical sized neighboring space through negotiating a price to compensate the previous tenant to move. By now, rent on both units was up to $1000 a month. The previous tenant built a 500 sq. ft. second floor at a 10' height. I've extended that to the full 750 now. On the first floor, there was a nice office build out in one front corner behind the man door & window. I knocked a door between that office & my front showroom & continued my VCT tile into there.
The rest of that new first floor environment was unfinished exposed studs & ceiling joists, with no electrical in the unit. It is now insulated for soundproofing, sheeted painted & wired with surface mount conduit for my 5x10 CNC router, dust collection, panel saw & my plans to dabble in some welding & light metal fabrication on the one remaining concrete floor section.
Above that, on the second floor, all my tool storage & large fabrication area exists again with the luxury of a roll door height allowing for forklifting or otherwise manipulating large items more easily between floors. That production area has another door & 3 steps up from the original 2nd floor & a minimum of electrical to power the vacuum pump & compressor for the CNC, the lighting, and a couple circuits for tools. Our tool storage shelves & 12 foot bench is enclosed next to the soundproof pump room, creating a 10' x 30' third floor mezzanine which is our painting area for all but the largest projects which are done in the larger adjacent third floor area over the original unit.