On a deck, though, sap of any kind is a pain. The sugars can feed the growth of mildew, and they become sticky and grab dirt. Resin-rich sap, including pine sap, is particularly sticky. It holds tenaciously to decks and other surfaces and hardens as it dries, becoming very difficult to remove.
Regular cleaning goes a long way toward removing sap from decks when it’s easiest to dislodge. A bit of clear hand dishwashing soap in water and a fine-bristle brush or a sponge mop is safe on all kinds of deck surfaces, provided you rinse thoroughly with water from a hose. If you want to use a deck cleaner instead of dishwashing soap, check the label to make sure it’s suitable for the type of decking you have. Products that work on wood or composites of wood and plastic may damage decking made or capped with PVC plastic. The opposite is also true. Work in sections so the soapy water doesn’t dry before you rinse, and have some old towels handy to sop up standing rinse water.
But with hardened sap — and even fresh sap from pines — this probably won’t be enough. Your best option depends on the type of decking you have.
If you have a wood deck, try using a little turpentine to dissolve the resin, suggested a customer-care representative for Olympic, a brand of PPG Architectural Finishes. Olympic makes sealers and finishes for wood decks, including oil-based, penetrating stains and sealers as well as water-based products that color wood with different levels of opacity. Turpentine should not damage any of the finishes, she said, but she cautioned to always test first in a small, inconspicuous area to make sure.
You’ll find advice online about using denatured alcohol to dissolve sap on wood decks. Olympic does not recommend that, both because it’s less effective than turpentine and because it can soften some deck finishes, the customer-service representative said.
Other advice online says to use undiluted Murphy Oil Soap because the oil in it will dissolve pine pitch. Not so, said a customer-service representative for Colgate Palmolive, which owns that brand. She said the 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 the soap should never be used undiluted. Also, the company debunks the idea that oil in the 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 the raw material, once the ingredients are transformed into soap, no ‘free oil’ remains in the final product.”
For a composite deck, the best approach depends on whether you have something made of a mixture of wood fibers and plastic that has the same consistency throughout, or capped decking, which adds a plastic shell around the wood-and-plastic mixture. Formulas vary, so if you know the specific brand you have, check with the manufacturer. Otherwise, always test an inconspicuous place first.
Trex, which switched to making only capped decking around 2010, recommends Citra Solv ($14.82 for an eight-ounce bottle on Amazon) to remove hardened sap on its capped decks. Moisten a sponge with a diluted solution, rub until the sap dissolves, then thoroughly rinse until the water runs clear, a customer-service representative said.
For older decks with uncapped composite boards, Trex doesn’t have any fail-safe suggestions. You could try placing a bag of ice over dried pitch, which may make it possible to peel off the pitch 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 so you can scrape it off. “Use a very light application,” she said. “Just on the sap and not the surrounding boards. But test it first in an inconspicuous place.” It might not work, though, or it might be too time-consuming if you have extensive sap deposits.
In that case, your only option is to figure out a way to scrape off the deposits without damaging the decking. Plastic razor blades sold by Lee Valley are soft enough to use on nonstick surfaces and automobile paints and would be less likely to dig into composite decking than a metal scraper would be. The plastic blades come in orange or yellow — the orange style being softer and more flexible. One 4-inch-wide blade in a holder is $4.50.
And if you have a PVC deck — all plastic, without any wood fibers? Use a deck cleaner that’s labeled as safe on PVC, said Jeronimo Ramirez, who sells TimberTech’s Azek PVC and capped composite decking through Advantage Lumber. (TimberTech Composite Deck Cleaner — which despite the name is not suitable for older composite decking but is fine on PVC and capped composites — is $43.49 a gallon on Amazon.)
If the sap is fresh, wait 15 minutes after diluting and spreading the cleaner as the label advises; if the sap is more than a few days old, wait longer, Ramirez said. He then rinses with a power washer. Or use a natural-fiber scrub brush and a hose for rinsing, as instructions for TimberTech Composite Deck Cleaner suggest.
Above all, Ramirez said, do not use vinegar — a sap-softening remedy that works well on car windows. Vinegar eats into PVC and makes sap stains on this kind of decking permanent, he said.
Have a problem in your home? Send questions to localliving@washpost.com. Put “How To” in the subject line, tell us where you live and try to include a photo.
