Decks are a selling point in real estate. But decks can take a pounding during an active summer. Since this tends to happen mostly beneath the boards, homeowners may overlook the warning signs until it’s too late and becomes costly damage, says Dave Kile, owner and deck expert at Trex Protect.
“Summer fun can take a bigger toll on your deck than most homeowners realize,” Kile says, adding that everything from melted ice to sugary spills and overloaded gatherings can accelerate rot and loosen fasteners. “Grease, spills and moisture don’t just stain the surface—they seep down and attack the structure,” he adds. “By the time you see signs of damage on top, the problems underneath may already be costly.”
Deck repairs run, on average, between $750 to $2,500, according to HomeGuide, a portal for finding local service professionals.
Kile shares five common types of deck damage, and how to spot them:
1. Dark stains between the deck boards
“Dark stains usually mean BBQ grease or liquid has seeped past the decking into the joists,” Kile says. “Left untreated, it becomes a food source for mold and speeds up rot.” However, the fix can be simple, he says.
What to do: Kile recommends applying a degreasing cleaner. Scrub between the boards with a stiff brush and then rinse thoroughly. For older decks, you may need to lift a board or two to clean hidden buildup.
2. Wobbly railings or loose boards
“That’s usually just wear and tear from people leaning, sitting or moving around during gatherings,” Kile says. “The fasteners get stressed. The good news is, it’s an easy fix.”
What to do: Inspect the joints, tighten the screws, swap out any rusty brackets and make sure you’re using weather-resistant fasteners, Kile says. “That should restore the stability,” he adds.
3. Soft spots underfoot when walking across the deck
Soft spots are a red flag and shouldn’t be ignored, Kile says. “They usually mean water or grease has gotten into the joists or beams underneath,” he says.
What to do: Get underneath and check the framing, Kile says. “If the wood is spongy, reinforce or replace it right away,” he says. “Leaving it will only make the problem worse.”
4. Scratches and gouges on the surface
Most of the time these are just cosmetic blemishes, but they are still worth fixing, Kile says. “Dropped items, or furniture being dragged, can strip off the protective finish, which then lets moisture seep in,” Kile says.
What to do: A light sanding works for small marks, Kile says. For deeper ones, use a filler that matches your deck material and then reseal it so water can’t get in.
5. Green or black patches along the joists
This is a telltale sign of mold or mildew—and it feeds on trapped moisture, Kile says. “It spreads fast, so tackle it straight away,” he says.
What to do: Kile recommends a scrub with a deck cleaner or diluted bleach solution. Then look at airflow and drainage. “Mold comes back if the deck can’t dry out properly,” he says.