semi-permanent floor system

Dear Wbsterritt, First level the dirt floor as much as practical. Then build a short (4 inch) pier and joist frame, like building a deck, only on the ground. Before actual assembly lay plastic sheeting for vapor barrier. After assembly of "mini" deck frame lay flexible PVC tubing between joists. This gives you radiant heating. Make the deck panels removable (like the floor in a computer room used to be) and you can route plumbing for your bath.

Regards Dragon

In my workshop I levelled the floor, used some soft sand to help fill some of the unevenness, then laid 8x4 sheets of 2" rigid foam insulation with a tongue & groove 18mm chipboard floor on top. It's firm enough to stand a fair bit of weight & stays reasonably warm.

I have asphalt in my garage, and it seems to work ok. To move heavy things around, such as with an engine hoist, I went to the local metal scrapyard and got some steel plates I can place wherever I need to go, otherwise my steel casters dig right in (bear in mind, Im usually moving 600-700 lbs on 3" dia wheels). If I ever decide to rip it up, I know I can probably strip it all out in an afternoon with some basic tools. For a small area like the one you are describing, this might be a cost and time effective route for you to go, as you can easily have it done in a few hours.

Avery Montembeault