Going for something a smidge bigger than yours Jeff: 63' by 34' (19.2 x 10.5 metres for those of us who subscribe to the French system of measurement in the crowd).
Anyhoo, here's the first doodles.
Plan with section line shown:
And section:
This is something that could be achieved in distinct stages:
1. Cut & fill and placement of DGB 20 (roadbase) and plant out the perimeter.
2. Bring in the container; 40 foot high cube, half office half storage, so it will have windows and doors cut into it at one end.
3. Pour the slab; 150mm 25mPa with a 250mm turndown at the edges. Place the container in its final position.
4. Build the retaining wall needed at the end nearest the house.
5. Chemset spiggots into the slab and erect portal frames. I'm not sure which to use: Steel or Composite timber, this will come down to cost and ability to support dead loads when lifting machinery, turning hulls and so on. Timber frames will need some clearance from the ground as per Gary's point about termites.
6. Whack on the roof. This will happen immediately after the frames have been erected if they are to be timber.
7. Clad the sides and put in doors, roller doors, louvres and vents.
8. Start putting machinery in/install timber floor over slab keeping an apron of slab clear to allow for protection against to ol' termites.
I reckon 6 months including approvals from my local council and about $20-25k AUD: What say ye all?