Is Stamped Concrete Slippery?
There are many people under the impression that stamped concrete is slippery. I have slipped on a few decorative concrete slabs myself, but it wasn’t the concrete that was slick: it was the sealer.
Stamped concrete is not much different from regular concrete when it comes to slip-resistance. The difference is in the sealer used. Outdoor decorative concrete is typically sealed with a clear acrylic top coat to repel moisture and enhance the concrete’s color. The sealer creates a plastic-like film when it dries. Since the sealer doesn’t readily absorb moisture, water pools on top. If you’ve ever seen children playing on a Slip-n-Slide, you know exactly what can happen with water atop plastic. It becomes as slippery as ice! Water atop acrylic sealer is no different, especially if the sealer is applied too thickly.
So what can a contractor do to insure against slippery stamped concrete? There are several solutions. The first is to leave a more “open” surface to stamp. Instead of using a fresno or hand trowel to finish the slab in preparation for stamping, he could use only a float. While many stampers prefer a very smooth finish to give them a ”fresh canvas” for texturing, trowelling a slab makes it overly slick. Simply floating the concrete instead leaves a sandier finish which aids with slip resistance. As a bonus, it can also make the texture look more realistic, especially on stone or brick patterns.
Another reason that some decorative concrete is slippery is that it has been over-sealed. The solution is simply to avoid applying too much sealer. One may think that a thicker coat of sealer is better, but consider that cured sealer is similar to plastic film. A thin coat of plastic gives the same protection against moisture as a thick one. No matter how thick the sheet of plastic is, water will not penetrate it. Using more sealer than needed provides no benefit. Instead, applying sealer too thickly fills in many of the slab’s tiny crevices, surface pores, and sand particles which would normally create traction. The smoother surface leads to slick stamped concrete.
Oversealing concrete can cause even more problems than just loss of traction. For instance, it can render the concrete unbreathable, which leads to hazing or whitening of the sealer. This is often referred to as “blushing”. It happens because moisture trying to evaporate from inside the slab becomes trapped beneath the thick seal coat. A thinner layer of sealer allows moisture to migrate more freely. As an added benefit, a thinner coat of sealer gives the slab a more natural matte finish as opposed to making it look glossy and artificial. For more on blushing, please read the article entitled “Should I Reseal My Concrete”.
While both of the above ideas can help a great deal, the simplest way to increase slip resistance on stamped or decorative concrete is to introduce a non-skid additive to the sealer. This is also the best way to fix already slick concrete. Skid-resistant additives can include silica sand, micronized polymer beads, glass beads, or any other gritty material. Depending upon the size of the particles, non-skid additives (such as H&C Shark Grip) can be invisible on the surface of the concrete. The stamped concrete in the photo above was sealed with one coat of acrylic sealer with Shark Grip additive. In addition to giving the surface the feel of shark skin or extremely fine sandpaper, it also helps to “matte down” the finish and make it less glossy.
By implementing the ideas above, one can drastically reduce the chances for dangerous slips, falls, and potential lawsuits. There is no reason why strolling on stamped concrete cannot be just as safe and comfortable as walking on any other hard surface.