If it's only 4 feet clearance under there I would just pave it w/the pavers from HD and store tools etc. under there, it is going to be a chore trying to crawl around under there and if you try and grow anything it is a chore to tend the plants, weed, etc. also it would breed mosquitoes because water would tend to stand and not dry off....sally

Appreciate the info on the Deckstone, I like how the tiles look and the materials sound so much better than composite deck materials. Never understand the logic of putting material that would rot or go bad into a product for exterior use, like putting wood in the composite wood, and those masonite sidings that had paper in it? It is like waiting for disaster to happen. Tried to figure out if 'regular' exterior tiles weight less than Deckstone, and found this site:http://www2.daltile.com/exteriors.cfm. It lists a lot of choices just not able to get the info of the weight per sq.ft. like Deckstone has listed. John made some excellent points, I would need steel frame for a concrete deck. That would be costly. I am leaning on tiling the deck. So far after talking with two contractors, I basically had to redo the decking to hold the extra weight of the tiles. I am waiting for my handyman to come and confirm the cost and whether he is comfortable to do it or not. I think he is pretty honest to let me know his comfort level. I will let you know how that goes. If you find anything else please let me know.

See how good I was being Jeff,I knew if I waited long enough I woudent have to mention the T=junk thing. I do a lot of solid skirting with cross vintalation installed, square lattice on a close pattern like 2'' looks nice. J

The following photos are of a system called Underdeck Oasis here's the link: http://www.underdeckoasis.com/ We had them come and install this as the ceiling of an under deck shed we built for customers of ours about a month or so ago. Metal panels in various colors with a drainage and gutter system. We also had them install it under the decking joists, instead over the top. This gives room for any torrential rain or lots of snow room to move and flush through the drainage system. The system has worked great, and we've had the crazy weather this year to put it through the tests, and passed it all. Good luck !