How To Make A Waterproofed, Strong Screw Hole

The best way to make a waterproof hole for strong attachment is:
1) Completely paint correctly-sized hardwood with barrier coat epoxy or barrier coat epoxy paint system (Must use prep and primer!).
2) Drill rough screw holes (Push hard & fast and pull out with as little rotation as possible.), 1/16″ oversized from max. screw thread diameter.
3) Fill holes carefully down a side, making sure to leave an air escape hole, with a structural epoxy paste. While chopped fiber is strongest, it will trap air and so is not recommended here. WestSystem 406, with 422 for barrier coat is ideal. Add 20% 422 first to get a waterproof mix and then 406 until it's about the consistency of whipped cream. Slowly plunge a straw into it, pinch the straw to hold the epoxy in, carry over to the hole and blow to deposit the epoxy at the bottom, then tamp it with the straw. At no stage in this process do you suck epoxy into the straw! That is very dangerous, on a number of levels!
4) Screw carefully by hand with screw coated in grease – (Including the underside of the head!), making sure the tip is not sticking, wipe off excess and leave screw in place until epoxy sets. Try this on a test piece first.
You’ve got a waterproof, amazingly strong screw hole, custom-threaded! When you seat the screw permanently, use a lock washer: You’ve turned your screw into a bolt.
The important bit to remember here is not any oil property of wood but the roughness of the hole, as well as the hardness and strength of the wood. Almost any hard wood is just fine, as long as it’s not brittle and many are much cheaper than teak. No matter what wood or other material is used, it must be truly waterproofed. Many materials appear impermeable and aren’t, over time. Screw holes are the most obvious places for rot but any surfaces that rub are also suspect, so make sure everything’s fastened properly and watch out for later mountings: I prefer to stick, rather than screw workman’s loops, mounting plates, etc.