I have two greenhouses and they both have the same flooring. First I spread a 2-3 " layer of mulch. I prefer cypress mulch simply because it lasts longer, but any hardwood mulch would work fine. I then covered this with a heavy-duty, vinyl cloth that I puchased from The Greenhouse Catalog. It comes in different pre-cut sizes and is black. It is tough as nails. I just pinned the edges every few feet with fabric staples which can be purchased from this store or from a big-box store such as Lowes. That's it. You end up with a soft, comfortable, durable walking/standing surface, that is porous to water. It has been ideal. My first floor is now 3 years old and looks like new.
I hope this helps you. Also check Greenhouse Megastore to compare prices for flooring and shade cloth, which both of my greenhouses have to have.
Ken
