On a bridge, however, sap of any kind is painful. Sugars can feed mold growth, they become sticky and trap dirt. Sap rich in resin, especially pine sap, is particularly sticky. It adheres firmly to decks and other surfaces and hardens as it dries, making it very difficult to remove.
Regular cleaning goes a long way in removing sap from decks when it is easier to dislodge. A little clear dish soap in water and a fine-bristle brush or sponge mop are safe on all types of deck surfaces, as long as they are rinsed thoroughly with water from a hose . If you want to use a deck cleaner instead of dish soap, check the label to make sure it’s appropriate for the type of deck you have. Products that work on wood or wood-plastic composites can damage decks made or covered with PVC plastic. The opposite is also true. Work in sections so the soapy water doesn’t dry before rinsing, and have old towels on hand to absorb stagnant rinse water.
But with hardened sap – and even fresh pine sap – that probably won’t be enough. Your best option depends on the type of deck you have.
If you have a wood deck, try using a little turpentine to dissolve the resin, suggested a customer service representative for Olympic, a brand of PPG Architectural Finishes. Olympic manufactures wood deck sealers and finishes, including oil-based penetrating stains and sealers, as well as water-based products that color wood with varying levels of opacity. The turpentine shouldn’t damage any of the finishes, she said, but she cautioned to always test in a small, inconspicuous area first to make sure.
You can find advice online about using denatured alcohol to dissolve sap on wooden decks. Olympic doesn’t recommend it, both because it’s less effective than turpentine and because it can soften some deck finishes, the customer service representative said.
Other tips online suggest using Murphy’s oil soap undiluted, as the oil in it will dissolve the pine pitch. That’s not the case, said a customer service representative for Colgate Palmolive, which owns that brand. She said soap can be diluted in plenty of water and used to clean a deck that has a finish or has been sealed within the last five to seven years, but soap should never be used undiluted. Additionally, the company debunks the idea that the oil in soap dissolves pitch. In the FAQ section of the Murphy Oil Soap website, the answer to the question of whether there is oil in the soap is: “No, there is no oil in Murphy® Oil Soap . Although pine oil is used as a raw material, once the ingredients are made into soap, there is no “free oil” left in the final product.
For composite decking, the best approach depends on whether you have a material made from a mixture of wood fibers and plastic that has the same consistency throughout, or a covered decking, which adds a plastic shell around the wood mixture and plastic. Formulas vary, so if you know the specific brand you have, check with the manufacturer. Otherwise, always test an inconspicuous area first.
Trex, which began making only clogged decks around 2010, recommends Citra Solv ($14.82 for an eight-ounce bottle on Amazon) to remove hardened sap on its clogged decks. Dampen a sponge with a diluted solution, scrub until the sap dissolves, then rinse thoroughly until the water runs clear, a customer service representative explained.
For older decks with uncovered composite boards, Trex does not offer any safety suggestions. You can try placing an ice pack on the dried terrain, which might help loosen the terrain without damaging the boards, the Trex representative said. Or try using a little GooGone Goo & Adhesive Remover ($3.59 for a 2-ounce bottle at Ace Hardware) to see if it softens the sap enough for you to scrape it off. “Use a very light application,” she said. “Just on the sap and not on the surrounding boards. But test it in an inconspicuous place first. However, this might not work or it might take too long if you have large sap deposits.
In this case, your only option is to find a way to scrape off the deposits without damaging the deck. The plastic razor blades sold by Lee Valley are soft enough for use on nonstick surfaces and automotive paints and would be less likely to dig into composite decking than a metal scraper. Plastic blades are orange or yellow – the orange style being softer and more flexible. A 4-inch wide blade in a holder costs $4.50.
What if you had a PVC terrace, entirely made of plastic, without any wood fiber? Use a deck cleaner labeled as safe for PVC, said Jeronimo Ramirez, who sells TimberTech’s Azek PVC and capped composite decking through Advantage Lumber. (TimberTech Composite Deck Cleaner – which, despite its name, is not suitable for older composite decks but is suitable for PVC and capped composites – costs $43.49 per gallon on Amazon.)
If the sap is fresh, wait 15 minutes after diluting and spreading the cleaner as the label directs; if the sap is more than a few days old, wait longer, Ramirez said. It then rinses with a pressure washer. Or use a natural fiber scrub brush and hose for rinsing, as the TimberTech Composite Deck Cleaner instructions suggest.
Above all, Ramirez said, don’t use vinegar — a sap-softening remedy that works well on car windows. Vinegar eats away at PVC and makes sap stains permanent on this type of deck, he said.
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