Our home is built into a hillside, the "crawl space" is huge so I've been slow but sure about creating a "caveman shop" over the last couple decades.
All it had was exposed floor joists and a plastic covered dirt floor with drainage already in place when I started.
Its taken some excavation to level it in places and a lot of 19" x 19" pavers and wall blocks since it has a couple different levels and lots of pea gravel, sand and crushed gravel.
I insulated the 2X6 exposed studs and put in sheet after sheet of plywood for the walls and to strengthen the sub walls in case of a big earthquake.
My big brother was an electrician, he helped me run a couple circuits to do lighting and outlets. I installed a 50k BTU natural gas heater for winter months even though being mostly under ground the temps don't go below 50 degrees even in mid winter. It's great in the summer, always nice and cool even when it's 90 outdoors and it's very quiet.
It continues to evolve and get finished out. I'm able to use an electric wench to bring motorcycles in and out when needed since it's about 5' down to the main floor from ground level. I've built storage out of cedar fence boards generated from replacing our fences from our rental home as well as this yard.
I don't know if I'll ever consider it "finished" until I run out of energy and or ideas for improvement.
Some in-process builds from over the years- I finally built a good size work bench that can be moved on it's own wheels pretty recently, it's great to have a spot for power tools, router and what not.
My son's 1985 XR350 is down there now, completely rebuilt and waiting for a local shop to finish up a left side case replacement on the motor.
These images are of the West half of the "crawl space" -for a little scale reference, that's my 15' Colman canoe and 15' Pygmy Kayak suspended from the ceiling.
I've redone my workout area in the East half and still finishing putting in the rest of the flooring consisting of 3/4" plywood supported by concrete blocks to deal with the unevenness due to rocks and concrete footings poured to support the posts that run through the middle forming a load bearing structure.
