I haven't done this, but find it a very appealing idea. I have a small greenhouse, and I'm thinking one obvious difference would be that you'll have to be more careful with water, in a finished interior space, than those of us with structures made of poly, metal, concrete, etc. I'm pretty neat when I water (filling a long spout watering can, no splashing of hoses) but I'm still used to being able to let the water run onto the greenhouse floor, as it drains. When you build the shelves, maybe you explore the idea of inset plastic trays, below some kind of grid, to catch run off? It's perfect that you've been able to use the space already in an unfinished state, since you're already familiar with how it works for light, temperature, and ventilation. Tile, patterned/stained concrete, or brick would all be good choices for the floor, since they could be done in a way that future homeowners would find acceptable, even if they aren't "plant people" or don't plan to use the room as a real garden work space. I also live in a very dry climate in the southwest, so I know that we can get away with things involving moisture in a house interior that simply would not work in other parts of the country. Sounds to me like you have the workings of a good plan.

Patricia Ann's Sunset.

Thanks... I think I learned somesthings from your pics. First of all, I've lost ventricosa Aureomarginata at least once, and the one I have just languishes along as a small plant... regular ventricosa does so well in deep shade, I never thought that vA maybe needs really bright light to get lush like yours... Second, my TOC has gotten larger by spreading and has much smaller leaves... never had the upright tall vase shape with large leaves like yours. Mine grows in full midday sun, so perhaps the shadier conditions lead to a totally different form. Both are striking, but yours just makes me even stronger on encouraging its selection as Hosta of the Year for 2013... I got June Fever for my sale this year simply because everybody walks by it on the way to the tables and wants "that bright one." The margins are a little unruly and unpredictable - but it is always a spring delight!

Usually the color of concrete is all the way through the material, so refinishing it is only going to give you more of the same unless you paint over it. I think you're better off getting a large format porcelain tile that's close to the look you want to float on top of this, but check with a flooring specialist to see if you will run into issues at the door thresholds.