I'm getting ready to start a remodel of a barn with a dirt floor into my woodshop. Does the regrind material need to have a particular substrate for this type of use (I've commonly seen 1/8" or smaller fine gravel suggested)?

Our Pre-Cut Regrind Rolls can be installed over any hard, flat surface. So as long as your dirt is fairly flat, you can easily install our rubber flooring over it. If it isn't, we would recommend placing some crushed granite over the ground to help level out the dirt and aid in proper drainage.