Exposed Aggregate Concrete Guide for Seattle: Look, Cost, Care
Last Updated: 5/11/2026Exposed aggregate sits at an interesting spot in the decorative concrete spectrum: more interesting than a broom finish, less attention-grabbing than a stamped pattern, and arguably more durable than either. The stone is the surface, and the stone is what wears. This guide walks through the aggregate options, how the finish is produced, when exposed aggregate is the right choice over stamped or stained concrete, and how it ages in Seattle's wet climate.
What exposed aggregate concrete actually is
In a standard concrete pour, the surface is finished smooth, hiding the aggregate beneath a layer of cement paste. Exposed aggregate inverts that: the top paste is removed during the curing window, leaving the stones as the visible surface. Because the aggregate is harder than the paste it replaces, the surface is naturally more durable and significantly more slip-resistant. Aged exposed-aggregate driveways and patios in the Seattle area often outlast the smooth concrete around them.
Aggregate options
| Aggregate | Look | Best for |
|---|---|---|
| Pea gravel | Classic, small smooth stones, neutral tones | Driveways, walkways — common and cost-effective |
| River-washed stone | Rounded shapes, warm browns and tans | Patios, pool decks — softer texture |
| Crushed granite | Angular fine stones, gray to pink palette | Walkways, accent panels |
| Basalt | Dark, dense, regional PNW stone | Modern aesthetic, urban patios |
| Specialty (green, blue, rust) | Color accents, more expensive | Feature panels, contrast borders |
Exposure methods
- Chemical retarder: a surface retarder is sprayed on the freshly placed slab. The top paste stays workable while the lower concrete sets. After several hours, the surface is washed with water and a brush to reveal aggregate. This is the most common method for new pours.
- Seeded aggregate: decorative stones are scattered onto the wet surface and rolled in. After initial set, the surface is washed to expose the seeded stones. This method allows specialty aggregates that would be uneconomical to mix throughout the slab.
- Surface grinding or sandblasting: applied to cured concrete to expose existing aggregate. More common in restoration than in new construction.
When to choose exposed aggregate
Exposed aggregate is the right answer when slip resistance matters (pool decks, sloped walkways, north-facing patios in shade), when the project wants visual interest without the maintenance overhead of stamped or stained finishes, and when long-term durability is the priority. It is also a good choice when the aesthetic goal is "natural" rather than "manufactured" — pebble-finished patios read as organic and age into the landscape rather than out of it. Stamped concrete is a better choice for projects that need to imitate a specific material (slate, brick, flagstone). Stained concrete fits when color is the design goal. For pattern detail, see the stamped patterns guide; for color, see the stained colors guide.
Cost factors and ranges
Exposed aggregate runs higher than a standard broom finish but generally lower than stamped concrete. The cost drivers are aggregate type (specialty stones add substantially), pour size (smaller pours have a higher cost-per-square-foot), site conditions (slope, access, base prep), and whether the design includes seeded specialty aggregates as accents. Ranges only — confirm with on-site estimate. For broader pricing context, see the concrete contractor cost and concrete patio cost guides.
Maintaining exposed aggregate in the PNW
Exposed aggregate is low-maintenance, not no-maintenance. Apply a penetrating sealer within the first year and reapply every three to five years to keep water out of the surface pores; the texture hides moss and mildew until it does not, so an annual rinse keeps growth from establishing. Pressure-washing at moderate settings is safe and effective on exposed aggregate, much more forgiving than on aged smooth concrete. For ongoing maintenance routines, see maintaining concrete and the freeze-thaw protection guide.
Pacific Northwest factors
PNW conditions favor exposed aggregate. Slip resistance is a real benefit in the wet season; the textured surface drains and dries faster than a smooth finish; the natural stone palette ages gracefully under mild PNW weather. Basalt is a common regional choice that fits the area's color sense. Drainage detail at the slab edges is the install-time consideration — exposed aggregate sheds water cleanly, so an edge that does not route the runoff produces a wet spot at the perimeter.
Frequently asked questions
What is exposed aggregate concrete?
Exposed aggregate concrete is a finish where the surface paste is removed during the curing window to reveal the stone aggregate underneath. The result is a textured, non-slip surface that shows the natural color and shape of the aggregate. It is one of the most durable decorative finishes because the stones doing the wearing are the strongest part of the concrete.
What kinds of aggregate are used?
Standard pea gravel produces the classic look. Decorative aggregate options include river-washed stone (smooth, rounded shapes in warm colors), crushed granite (angular, fine texture, neutral palette), basalt (dark, dense, common in the PNW), and specialty stones in greens, blues, and rust tones. The aggregate is specified with the batch plant before the pour.
How is the surface paste removed?
Two main methods: chemical retarder applied to the surface so the top layer stays workable longer and can be washed off, or seeded aggregate where the stones are broadcast onto the freshly placed slab and embedded with a roller. Some projects use surface grinding or sandblasting on cured concrete to expose aggregate, but those are typically restoration techniques rather than the primary method for new pours.
Is exposed aggregate slippery in the rain?
No — exposed aggregate is among the better non-slip finishes for wet conditions. The textured surface gives shoes and tires something to grip even when wet. That makes it a popular choice in Seattle for pool decks, driveways, and walkways where slip resistance matters in the rainy months.
How is exposed aggregate maintained?
Penetrating sealer every three to five years to keep water out of the surface pores, periodic pressure washing to remove organic growth, and occasional joint maintenance. The textured surface holds more debris than smooth concrete, so leaf removal and clearing organic matter is part of the routine. Exposed aggregate does not need polishing or resealing in the dramatic way film-formed surfaces do.
Plan an exposed aggregate project
Exposed aggregate is one of the easiest decorative finishes to get right when planned correctly. A free on-site assessment picks the aggregate, confirms drainage and base prep, and matches the look to the use case. Call (206) 552-9998 or browse decorative concrete services and concrete driveway services.
