# Why Your Pool Deck Gets Slippery and How to Fix It | Pressure Wash 901 > A slippery pool deck is usually algae biofilm, not soap or sunscreen. Why it is a safety issue, how surfaces differ, and how to care for Kool Deck. ## Why Your Pool Deck Gets Slippery and How to Fix It That slick feeling underfoot around the pool is almost always algae biofilm, and it can build up well before it is visible as green or dark staining. Published 2026-08-16 by Pressure Wash 901 · Memphis & the Mid-South ## What Is Actually Making the Deck Slippery That slick feeling on a pool deck rarely comes from soap residue or sunscreen, though people often assume that. It is algae biofilm, a thin living layer of algae and bacteria that grows on any surface that stays wet and gets some shade or splash-out from the pool. It can be present well before it is visible as green or black discoloration, which is why a deck can feel slippery before it looks dirty. Pool decks are ideal growing conditions: constant moisture from splash-out and humidity, warm temperatures for most of the year, and surfaces with enough texture for algae to grip onto. Even a deck that gets rinsed off with a hose regularly can still build up biofilm, since a quick rinse moves surface dirt but does not do much to disturb a biofilm layer that has attached itself to the surface. Humidity plays a role too. In the Mid-South, the air itself stays damp for long stretches of spring and summer, which means a pool deck may never fully dry out between swims even on days no one gets in the water. That constant low-level moisture is enough to keep biofilm growing steadily in the background. ## Why This Is a Safety Issue, Not Just a Look A slippery pool deck is one of the more common causes of falls around backyard pools, especially with kids running from the water, bare feet, and anyone stepping out wet. Because biofilm builds gradually, it is easy not to notice how slick the surface has gotten until someone slips. Cleaning it is not just about appearance, it is about keeping the walking surface safe. Shaded areas and low spots that hold water after rain or splash-out are usually the worst offenders, since those are exactly the conditions biofilm needs. Steps, the edges right around the pool, and any spot under an umbrella or covered patio area tend to build up faster than open, sunny sections of the same deck, which is worth keeping in mind since those are also the areas people walk through most while wet. ## Which Surfaces Are Affected, and How Plain broom-finished concrete, stamped concrete, pavers, and coated decking like Kool Deck all grow biofilm, but they show it differently. Concrete and pavers tend to get an obvious dark or greenish tint in shaded areas and low spots where water pools. Coated surfaces can feel slick even when the discoloration is subtle, because the coating itself has a smoother finish that traps a thin film rather than showing it as clearly. Broom-finished concrete has more texture to begin with, so it tends to hide biofilm buildup longer, but it also holds onto it more stubbornly once it takes hold, since the film gets down into the texture rather than sitting on a flat surface. Pavers have joints in addition to the paver faces themselves, and biofilm can build up in those joints even after the flat surfaces have been cleaned, which is why a thorough deck cleaning covers the joints as well as the pavers. ## Caring for Kool Deck and Similar Coated Surfaces Kool Deck and other acrylic coatings are more sensitive than bare concrete or pavers. High pressure or the wrong technique can pit, streak, or strip the coating, which is expensive to redo. These surfaces need to be pressure washed carefully, at lower pressure and with a steady, even pass, so the coating gets cleaned without being damaged. This is different from bare concrete or pavers, which can handle a stronger pressure and surface cleaner pass. A streaked or unevenly cleaned coated deck is usually a sign the pressure was too high or the nozzle was held too close in some spots and too far in others. Keeping a consistent distance and overlap across the whole deck is what produces an even result on a coated surface, rather than the blotchy look that comes from rushing through it or treating it the same as bare concrete. ## How Often to Clean It Pool decks that get regular splash-out and sit in partial shade usually need cleaning at least once a year, and doing it before the pool opens for the season works well since that is when biofilm has had all winter to build up. Decks in full sun with good drainage tend to stay cleaner longer than decks with shaded, low-lying areas where water sits. Pools that see heavy summer use, or decks bordered by mature trees or landscaping that keeps parts of the surface shaded most of the day, may need a second cleaning partway through the season to stay ahead of buildup. Checking the surface underfoot after it has been wet for a while, rather than relying on how it looks dry, is the simplest way to tell whether it is due for a wash. ### Free quote in 24 hours Send a few photos and your address. Written price, no obligation, valid 30 days. ### Related services - Patio & pool deck cleaning ## Questions **Q: What makes a pool deck slippery even when it looks clean?** Algae biofilm can build up on a pool deck before it is visible as discoloration. It is a thin living layer that thrives on the constant moisture around a pool, and it can make a surface feel slick well before it looks dirty. **Q: Is it safe to pressure wash Kool Deck?** Yes, but it needs to be done carefully. Kool Deck and similar acrylic coatings are more sensitive than bare concrete, and pressure that is too high or a nozzle held too close can pit or strip the coating, so lower pressure and a steady, even technique matter. **Q: How often should a pool deck be cleaned?** Most pool decks with regular splash-out and some shade need cleaning at least once a year, often best done before the pool opens for the season. Decks in full sun with good drainage generally stay cleaner longer than shaded, low-lying areas. ## Send a photo. Get a price. Flatwork at 12 cents per square foot, house washing around 18 cents, $149 minimum per visit. Written quote within 24 hours. --- Pressure Wash 901 · (901) 264-0572 · pressurewash901@gmail.com Collierville, TN 38017 · Monday to Saturday, 8am to 6pm Request a quote: https://pressurewash-901.com/quote.html Source page: https://pressurewash-901.com/slippery-pool-deck-fix.html