Exposed aggregate concrete in Pittsburgh, PA
Exposed aggregate removes the thin top layer of cement to show the stone underneath. It has a natural texture, it hides dirt and it gives good grip on wet Pittsburgh hills, which plain smooth concrete can't always match.
Job ticket: Exposed Aggregate Concrete
- Surface
- Natural stone
- Grip
- High when sealed right
- Sealer
- Every 2 to 4 years
- Best for
- Walks and sloped drives
Rough guide$11 to $18 per sq ft
What is exposed aggregate concrete?
All concrete is mostly stone. When a slab is finished normally, a thin layer of sand and cement paste floats to the top and covers it. With exposed aggregate, the crew uses a surface retarder or a timed wash to remove that layer before it hardens, leaving the rounded or angular stones showing. You can use the standard local stone or choose a decorative mix for color.
It is an old technique, and you will see aged examples on sidewalks and public buildings around Pittsburgh. Done well, it wears very slowly because you are walking on stone instead of paste.
Exposed aggregate walks and landings
An exposed aggregate walk makes the most sense on a slope, where grip counts in winter. On walks and front steps, it gives a richer look than broom finish, and it pairs well with brick. Patios work too, but the texture isn't comfortable underfoot for bare feet, and it can be harder on furniture legs. A broom-finished border around an aggregate field looks sharp and also makes joints neater.
Getting the timing right
The finish depends on washing the surface at the right moment. Too soon, and stones come loose. Too late, and the paste won't come off. Hot, windy days and cold mornings shift that window, which is why this job needs an experienced finisher. We wash the surface in sections and manage the runoff, since the cement water shouldn't go into storm drains or your plantings.
Sealing and salt
Seal exposed aggregate after it has cured, then every 2 to 4 years. A sealer protects the paste around the stones and deepens their color. Choose carefully, as thick glossy sealers can get slippery when wet. Keep rock salt off it, particularly in the first winter. See concrete sealing for options.
How it compares
| Finish | Typical price | Grip | Upkeep |
|---|---|---|---|
| Broom finish | $7 to $12 per sq ft | Good | Low |
| Exposed aggregate | $11 to $18 per sq ft | Very good | Seal every few years |
| Stamped concrete | $15 to $25 per sq ft | Lower when wet | Seal every few years |
How the work goes
- Pick the stone
We show samples and talk through colors and borders.
- Prep and form
Base and forms are built for pitch and clean edges.
- Pour and retard
Concrete is placed, finished and treated to slow the surface set.
- Wash and seal
We expose the stone at the right moment, then seal once cured.
Common questions
What is exposed aggregate concrete?
It is concrete with the top layer of cement paste removed to show the stones in the mix, leaving a textured pebble surface.
How much does exposed aggregate cost?
Usually $11 to $18 per square foot around Pittsburgh, depending on the stone, the shape and any border work.
Is exposed aggregate concrete more expensive?
Yes, it usually costs a few dollars more per foot than broom finish, because it takes extra labor and timing.
Is exposed aggregate concrete slippery?
No, the stone texture gives good grip. A thick glossy sealer can make it slick, so we use a suitable product.
What color is exposed aggregate concrete?
It takes on the color of the stone, usually grays and browns locally. Decorative mixes add reds, blacks and creams.
What does exposed aggregate concrete look like?
It looks like a bed of small stones set tightly in concrete, with a natural, slightly bumpy texture.
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