Exposed aggregate concrete is a decorative finish where the top layer of cement paste is washed away to reveal the stones, pebbles, and gravel beneath. In Calgary, it is one of the most durable and slip-resistant outdoor surfaces available – and it looks better at year five than most stamped or broom-finished alternatives.
What Is Exposed Aggregate Concrete?
Standard concrete is finished by smoothing or brooming the top surface. Exposed aggregate goes a step further: after the concrete is poured and partially set, a surface retarder is applied or the top layer is washed off to reveal the decorative aggregate below. The result is a textured, stone-studded surface with natural colour variation and a gritty grip underfoot.
The aggregate can be standard river gravel (rounded, smooth stones), crushed granite, quartz, or specialty pea gravel imported in specific colours. Local Calgary suppliers typically use Alberta river stone in earthy tones – grey, tan, rust, and brown – which blends naturally with the surrounding landscape.
How Is It Different from Stamped Concrete?
Stamped concrete mimics the look of stone, brick, or slate using moulds pressed into the surface before it fully cures. Exposed aggregate reveals actual stone. Both are decorative concrete finishes, but they perform differently over time. Exposed aggregate holds its texture because the material is embedded in the slab – there is no surface layer to chip, fade, or peel. Stamped concrete relies on a coloured release agent and sealer to maintain its appearance, which needs to be reapplied every two to four years in Alberta’s climate.
Why Exposed Aggregate Works in Calgary’s Climate
Calgary averages more than 100 freeze-thaw cycles per year. Water works its way into surface cracks, freezes, expands by roughly nine percent, and widens the crack. Surfaces that depend on a smooth or sealed top layer – broom finish, stamped, or brushed – are vulnerable to spalling, surface delamination, and flaking because the damage typically starts at the top and works downward.
Exposed aggregate has no smooth surface layer to delaminate. The stones themselves are embedded in the concrete matrix. Freeze-thaw damage can still occur, but it tends to affect the bond between individual stones and the surrounding paste rather than peeling the surface uniformly – and it happens significantly more slowly with a properly mixed, air-entrained concrete.
The Role of Air Entrainment
Any exposed aggregate installation in Calgary should use a concrete mix with six percent air entrainment. These microscopic air bubbles act as pressure-relief valves during freeze-thaw cycles – water that would otherwise crack the paste has somewhere to expand. Without it, even premium aggregate cannot compensate for a poor base mix. At Rosko Concrete, every exterior pour uses air-entrained, 32 MPa concrete minimum.
How Much Does Exposed Aggregate Concrete Cost in Calgary?
Exposed aggregate concrete in Calgary typically costs between $14 and $22 per square foot installed, depending on the aggregate type, project size, site conditions, and current material pricing. That range reflects the full installation: excavation, base preparation, formwork, concrete supply, finishing, and sealing. Always verify pricing directly with your contractor – material costs fluctuate with fuel and supply chain conditions.
| Project Type | Typical Size | Estimated Cost Range |
|---|---|---|
| Driveway (single car) | 40–60 sq m | $8,000–$14,000 |
| Driveway (double car) | 60–90 sq m | $12,000–$20,000 |
| Patio | 25–50 sq m | $5,000–$11,000 |
| Walkway | 10–20 sq m | $2,500–$5,500 |
| Pool surround | 40–80 sq m | $9,000–$18,000 |
These ranges are general market references as of 2026. Your actual quote will depend on your specific site – access, existing concrete removal, drainage requirements, and the aggregate grade you select. A site visit is the only way to get an accurate number.
What Drives the Cost Up
Several factors push exposed aggregate costs toward the top of the range: coloured or premium aggregate (imported quartz or river stone from outside Alberta), difficult site access requiring pump trucks, slopes that require additional drainage, and projects where existing concrete must be broken out and hauled away. Demolition alone can add $2–$5 per square foot depending on slab thickness.
What Keeps the Cost Down
Simple, flat sites with good access, straightforward rectangular shapes, and standard Alberta river aggregate are the most cost-efficient to install. Combining multiple surfaces in one pour – driveway plus walkway, for example – reduces setup costs spread across a larger area.
Exposed Aggregate vs. Other Concrete Finishes
| Finish Type | Estimated Cost/sq ft | Maintenance (Calgary) | Lifespan (with care) | Slip Resistance |
|---|---|---|---|---|
| Broom finish | $10–$15 | Seal every 3–5 years | 20–30 years | Good |
| Stamped concrete | $18–$30 | Reseal every 2–4 years | 15–25 years | Moderate (varies by pattern) |
| Exposed aggregate | $14–$22 | Seal every 3–5 years | 25–35 years | Excellent |
| Interlocking stone | $20–$40 | Re-sand joints, weed control | 20–30 years | Good |
Is Exposed Aggregate Slippery When Wet?
No – the opposite. The rough, textured stone surface provides significantly more grip than a smooth broom or stamped finish, especially when wet. This makes it a popular choice for pool surrounds, driveways in shaded areas that collect moisture, and front walkways exposed to rain and snow. The texture is consistent across the full surface, including edges and corners.
How Long Does Exposed Aggregate Last in Calgary?
A properly installed exposed aggregate surface – correct mix design, adequate base preparation, and sealed at appropriate intervals – can last 25 to 35 years in Calgary. The key word is properly installed. Exposed aggregate installed with inadequate base compaction, low-strength concrete, or no air entrainment will fail earlier regardless of how nice it looks on day one.
Maintenance is simple: seal with a penetrating or film-forming sealer every three to five years, avoid calcium chloride de-icers (use sand or magnesium chloride), and address any cracking early with crack injection before water infiltration accelerates damage over winter.
Common Mistakes with Exposed Aggregate in Calgary
- Using calcium chloride to melt ice – it attacks the cement paste and accelerates stone loss. Use sand or magnesium chloride instead.
- Skipping the sealer – exposed aggregate absorbs water without a sealer. In Calgary, that moisture freezes and accelerates wear.
- Under-specifying the concrete mix – 25 MPa is code minimum but insufficient for Calgary driveways. Specify 32 MPa with air entrainment.
- Poor base preparation – no amount of finish quality compensates for a base that settles unevenly. 150mm of compacted granular A is the standard for Calgary soil conditions.
- Washing the aggregate too early or too late – timing is everything. Too early and stones pull out entirely; too late and the surface paste is set. This is a skill issue, not a material issue.
Frequently Asked Questions
Can exposed aggregate concrete be repaired if stones fall out?
Yes, but repairs to exposed aggregate are more visible than repairs to smooth concrete because matching aggregate colour and distribution is difficult. Small areas can be patched with matching aggregate and a bonding agent. For significant areas, full replacement of the affected section is usually the better option. This is another reason proper installation is worth the investment – preventing damage is far easier than repairing it.
How soon can I walk on exposed aggregate concrete?
Light foot traffic is generally safe after 24 to 48 hours, depending on temperature and humidity. Vehicle traffic should wait at least seven days, and ideally 28 days for the concrete to reach full design strength. In cooler Calgary weather – below 10°C – curing takes longer and extra precautions should be taken.
Does exposed aggregate cost more than a regular driveway?
It costs more than a standard broom finish – typically $4 to $8 more per square foot – because the finishing process requires more skill and time. The aggregate material itself adds cost if you choose premium stone. However, the longer lifespan and lower long-term maintenance costs make it competitively priced over a 20-year horizon compared to stamped concrete, which needs more frequent sealing.
What aggregate colours are available in Calgary?
Standard Alberta river stone comes in natural grey and earth tones. For different looks, contractors can source coloured quartz, black granite, white marble chips, or mixed-colour decorative stone. Premium aggregates cost more and may need to be ordered specifically for your project. Ask your contractor to show samples before committing to a colour – wet stone looks very different from dry stone.
Ready to add exposed aggregate concrete to your Calgary property? Request a free quote from Rosko Concrete – Jeff will visit the site, walk through your options, and give you a written estimate with no pressure and no obligation. We also offer stamped concrete, driveway installation, and concrete repair services across Calgary and surrounding communities.