I need to build a platform/base in a partially finished basement that occasionally floods. The flood isn't much, about 1/2 inch, but it does stick around for a bit (at least until the dehumidifier takes care of it). Anything made of wood gets soaked enough to weaken the wood, and is probably a good home for mold. My first thought was to use plastic/composite lumber, as it can get wet without any damage, but I can't find information on what brands are suitable for indoor use. I've heard that some brands have gassing issues. Is there a brand suitable for indoor use?
As long as your platform/base doesn't need to be structural, cellular PVC based decking/trim is acceptable for indoor use and that type of moisture exposure. Look at Azek's trim product line.