My Deck Board Is Leaking Sap

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Wooden decks offer an outdoor space ideal for relaxing or entertaining as well as increasing your home's value. Regular maintenance performed on your deck keeps it looking good, protects it against foul weather and extends its life. Owners with pressure-treated lumber decks should take precaution to clean or prevent sap leakage.


Treated lumber typically made from pine lumber contains natural sap that tends to leak until the wood is completely dry. Knots in the wood grain and the areas surrounding them typically leak the most sap along with cut edges of the board. Decks in hot and dry climates tend to leak the most due to the heat causing the sap to expand and seek ways out of the wood.

Removing Sap

The sap found coming from deck boards is extremely hard to get off due to its sticky consistency. A power washer is an ideal tool to remove the sap seeping from the decking along with removing any mildew and dirt stains. Turpentine is an age-old method of removing sap that works well on pressure-treated decks. You should take proper safety measures when utilizing chemicals to clean the sap, including wearing heavy-duty rubber gloves, protective eyewear and a breathing mask. Other methods to remove the sap include scraping it off with a putty knife or sanding it off.

Preventing Sap

To prevent sap from leaking out of deck boards, it needs to be finished with paint, stain or deck waterproofing. These materials slow the leakage by clogging the wood grain pores but will not stop it completely. Treat the knot areas with extra coats of the finishing material. Avoiding or replacing deck boards with knots helps eliminate areas where sap can leak and will cut down on your yearly maintenance.


The sap that leaks from deck boards is extremely sticky and will adhere to almost anything that comes in contact with it. Keep animals away from the areas, because the sap will stick to their fur and paws. Avoid using an expensive saw blade when cutting the deck boards, as the internal sap sticks to the blade, causing excess friction and heat, which can warp it. Avoid using harsh cleaning agents, if possible, as they can change the color of the wood and prevent future finishes from adhering properly.


Matthew Knight

Based in Southwestern Michigan, Matthew Knight has been writing outdoor and technology articles since 2008. His articles appear on various websites. He holds a bachelor's degree in computer information systems from Western Michigan University.