How to construct a weatherproof outdoor wooden sign, and what to finish with?
Nek,. You new a water sealer. Thompson wood water sealer clear, should do the trick. Aloha!
Helmsman Spar Urethane.
Use numerous coats of the urethane and it will be good for many years. I also use marine polyurethane in many coats, it is made for constant differing weather and moisture.