This post was updated on March 1, 2022
Clear Sealer or Poly over a Deck Stain?
We here at DeckStainHelp.com thank you for your continued support as we continue to be the internet’s number one reference for all things wood deck restoration related. If you have ever considered using a polyurethane coat to give your outdoor wood deck a smooth appearance, read this article and really think about the potential repercussions. As always, we appreciate your input, so feel free to leave a comment below.
Deck stains are meant as a protective finish for exterior wood. They contain special UV shielding pigments and mildewcides to ward off mold and mildew and to keep the wood from fading. Other sealers or clear finishes will not adhere well to a deck stain and may result in the topcoat failing prematurely. Most likely the clear sealer or polyurethane will end up peeling and flaking off the deck stain.
Unlike paint, stains and sealers are not necessarily designed to adhere to each other. Most are designed to penetrate into the wood or at least adhere to the bare wood in the case of film-forming stains. Applying a clear sealer over a deck stain is never a good idea. It really won’t help the deck stain or give any added protection more than the deck stain already is. Clear sealers have no pigment and therefore provide zero UV protection. The same goes for polyurethane.
If you are looking for a more shiny finish on your exterior wood surface, it is best to choose a deck stain that will give you the appearance you are looking for. Applying a clear sealer or polyurethane over a deck stain will cause more problems than it is worth. If you want a clear finish then you can strip off any old stain and start fresh with bare wood. Then you can apply a clear sealer if that is the look you are going for. Just remember that you won’t get any UV protection from a clear sealer, only water protection.
In addition, applying polyurethane over a deck stain will make it near impossible to maintain the deck down the road. As the deck stain begins to fail underneath the polyurethane it won’t be possible to clean and recoat it without stripping off all the polyurethane first. So can you apply a clear sealer or polyurethane over a deck stain? It is not recommended and should really be avoided if possible.
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As an article and comment contributor to the site, Scott has been around the pressure washing industry since attending college. In 1993 he started his first company called Oakland Pressure Wash specializing in exterior pressure washing and deck staining. That company evolved into OPW L.L.C. shortly thereafter concentrating more on exterior wood and deck restoration. Scott and his Deck Cleaning Michigan company have restored over 10,000 decks in the Metro Detroit area since the early years. He has become an authority in the deck restoration industry and has contributed to numerous wood restoration forums and informative sites.
All the products he suggests through this site are sold through online sites and in retail stores, allowing the consumer to choose their own means of purchase. Scott’s eCommerce sites do sell many top brands he endorses and if you appreciate any of the help he has offered then feel free to purchase from one of them.