Last post of the day, I promise. I am currently at Lowes and am looking at carbon-fiber mesh screens for the drainage layer. What is an appropriate size for the holes, should I be buying the smallest holes for say no-see-ums? Thank you all.
You only have 7 posts, RobRoyce! I don't think you are annoying anyone ;-)
Carbon fiber? I usually buy fiberglass screen at Lowe's/Home Depot. The size of the holes is not usually an issue for the drainage as long as it's window screen. It's mesh coverings over vents where the size of the mesh matters more because you can have mesh big enough for fruit flies to get out. For drainage, you are just trying to keep the substrate from getting down into the drainage layer. Most common window screen is just fine for this purpose. Just steer clear of the metal stuff.