I found I guy on craigslist that bought 18,000 sqft of different hardwoods from a closed down lumber mill. I really like the walnut he gave me some sample of but my builder says he is afraid to install it because it is only 9/16" thick and 4 1/2" wide? Does it really make that much different then 3/4" hardwood flooring? Thanks

There's gotta be something else to this story? Could be the fact it's closed down, may be strange odd lots that could be a nightmare to install. Could also have been sitting around forever....wherever, indoors, outdoors.

There are some manufacturers that specialize in thinner hardwoods but 9/16" isn't one of them when it comes to a solid.

Hire a hardwood expert to check it out. Like an NWFA inspector, go and pull alot of boards and check for warping and fit of the T&G. Most GC's don't know as much about hardwood as a hardwood guy does.