Can you make wood 100% waterproof?
You can’t permanently waterproof wood. No finish lasts forever without maintenance. Epoxy resin comes closest to permanent, lasting 10+ years before needing attention. For the longest-lasting results, use epoxy on indoor projects or marine-grade spar varnish plus exterior paint on outdoor wood. The most affordable way to waterproof wood is by starting with a natural wood oil and following with a coat or two of outdoor paint. Though more budget friendly in the short term, you will need to redo this method more frequently, as it is not as long lasting as, say, a pricier, high-quality sealant.