Where the numbers come from
Sherwin-Williams tells homeowners to plan on staining a deck every 2–3 years, depending on climate and wear. On a page for one of its deck stains, it says to reapply every 12–48 months. The spread is wide because finishes differ: a thin, see-through stain on a sunny, busy deck wears faster than a heavier finish on a shaded one. Use the range to put a check on the calendar, then let the deck tell you whether it needs a coat.
For a new pressure-treated deck, Sherwin-Williams says to wait at least six months before the first stain so the wood can dry out.
A yearly check that tells you what the deck needs
NADRA, the North American Deck and Railing Association, whose mailing address is in Quakertown in Bucks County, recommends that homeowners check their decks often and consider a professional inspection at least once a year. It promotes May as Deck Safety Month, which is a good time to do the walk-around before the deck sees heavy use.
Sort what you find into three piles:
Dirt and debris. Leaves and grime only need cleaning. NADRA notes that built-up debris can be slippery and encourages mildew.
A worn finish. If the coating has worn away or mildew keeps coming back, NADRA says to clean the deck and apply a new protective coat. Peeling or flaking finish needs more preparation than a wash, which is covered below.
Wood or hardware problems. Wood that’s soft or spongy, or that a screwdriver sinks into ¼ to ½ inch, may be decaying, according to NADRA’s checklist. Loose or rusted fasteners, a sagging or swaying deck, or loose railings and stair parts also go on a repair list. A fresh coat of stain won’t fix any of these. Our guide on when deck joists or posts need a professional inspection explains what to look for from a safe spot, and why deck boards cup or split covers board movement.
A quick photo of the same boards, stair treads and railing sections each year makes it easier to see whether wear is getting worse.
The water-drop test, and what it can’t tell you
Sherwin-Williams’ test is simple: sprinkle water on the clean deck. If the drops soak in, the wood is ready for stain. If the water beads up or doesn’t soak in, old sealer is probably still there. Sherwin-Williams warns that a new stain or sealer applied over leftover sealer will likely not stick, so in that case the old coating has to come off first.
Try a few spots, including sunny boards and shaded ones, since one sheltered board doesn’t speak for the whole deck. The test only tells you whether the surface will take stain. It says nothing about whether the framing is sound.
Before you buy a finish
Find out what’s on the deck now. The old can, a receipt or a past contractor’s invoice helps. Sherwin-Williams says some stains and sealers don’t adhere well to others, which is why it recommends removing the old finish before switching products. Its old-deck instructions also call for a surface that is clean, dry and free of mildew, and a forecast with no rain for 24–48 hours.
After that, follow the label and the product data sheet for the finish you pick, including drying time, recoat time and when you can walk on it. Sherwin-Williams notes that drying and recoat times depend on temperature, humidity and how thick the coat goes on.
Which pro to call
For cleaning and refinishing, a deck-refinishing or painting contractor is the right call. Ask for a written scope that names the cleaner, the prep method (cleaning only or stripping), the finish, and the weather conditions they need, and ask them to explain why the deck needs a new coat now rather than just a cleaning.
For soft wood, loose railings, sagging, or anything that looks like it’s pulling away from the house, call a deck contractor or a home inspector for an evaluation first. NADRA says its checklist is meant to help homeowners and isn’t proof that a deck meets code. Keep people off any area that looks unstable. If the fix means replacing framing, stairs or railings, check whether the deck repair needs a permit in Philadelphia or your Bucks County township before work starts.