I am getting smarter this year and stacking my wood closer to the house, near where I use it. I have plenty of extra room in my driveway - if you were stacking wood directly on pavement, would you still put something underneath the wood? Seems a bit unnecessary, but even on pavement the bottom layer is going to get wet, and occasionally sit in a bit of water after a rain. Is it worth the hassle of putting down old pallets or other material first?