Exposed Aggregate Contractor
in Seattle, WA

There is a reason exposed aggregate concrete has been the finish of choice for Pacific Northwest driveways, patios, and walkways for generations. It is not nostalgia. It is physics. By washing away the cement paste from the surface of freshly poured concrete and revealing the decorative stone embedded within the mix, you create a surface with a naturally irregular, multi-point texture that provides outstanding traction in wet conditions. In a city that receives over 37 inches of annual rainfall and whose residents are walking, running, and driving on wet surfaces for nine months of the year, that traction advantage is not a minor benefit. It is a primary design consideration. The exposed aggregate process looks deceptively simple from the outside, but timing is everything. After the concrete is placed and screeded, a surface retarder is applied to the top of the slab to slow the set of the surface paste while the concrete beneath continues to harden normally. At the precise moment when the base concrete has reached the right strength — typically several hours after the pour, depending on temperature and humidity — we pressure wash the surface to remove the retarded paste and expose the top layer of aggregate. If we act too early, the stones pull out and the surface is ruined. If we wait too long, the paste has hardened and cannot be removed without damaging the stones. This is craft work, and our experienced crews have the eye and the timing to execute it correctly every time. The aggregate itself is where the design decisions become interesting. Standard ready-mix concrete contains whatever local aggregate the batch plant uses, typically a combination of rounded river rock and crushed stone in a neutral gray-tan palette. For clients who want more visual impact, we work with specialty aggregate mixes that incorporate river pea gravel in warm brown and rust tones, black basalt for a dramatic dark contrast, or quartz and granite chips that catch the light with a subtle sparkle. The aggregate color and size are selected to complement the specific architecture and landscape of the property, and we always provide samples before committing to a mix design. Exposed aggregate is particularly well-suited to Seattle's specific surface applications. On driveways, the texture handles tire wear and the visual demands of street-facing prominence equally well, and the natural variation in aggregate color conceals the inevitable tire marks and surface staining that accumulate over time on any driveway surface. On patios, the surface feels comfortable underfoot, does not retain heat the way dark-colored smooth concrete does, and provides the grip needed around outdoor kitchens and bar areas where spills are inevitable. For pool decks, exposed aggregate is often the recommended finish because of the maximum wet traction it provides around water, and the ability to select light-colored aggregate that reflects heat and remains comfortable to walk on barefoot. Because exposed aggregate surfaces have a slightly more porous character than troweled or broom-finished concrete, proper sealing is particularly important. We seal every exposed aggregate surface we install with a high-quality penetrating silane-siloxane sealer that locks out moisture and prevents the oil and chemical staining that can discolor the aggregate over time. This sealer also makes maintenance dramatically easier, as dirt and debris wash off the textured surface cleanly without accumulating in the aggregate voids. Exposed aggregate pairs beautifully with smooth concrete borders and stamped concrete accent panels. Many clients choose a decorative banding of stamped or stained concrete around the perimeter of an exposed aggregate driveway or patio, creating a finished, intentional appearance that elevates the overall design. Call Cloud Concrete of Seattle at (206) 495-0997 to discuss aggregate options and get a free estimate for your driveway, patio, or walkway project.