Concrete garage pads are expected to withstand years of vehicle loads, seasonal temperature changes, and daily wear. But when cracks begin to form in the curbs and water pools on the floor, it’s a sign that something went wrong during design or construction. This article explores the structural issues uncovered during a recent inspection of a residential garage pad in Calgary, Alberta.
Surface Appearance vs. Structural Reality
At first glance, the garage pad appeared well-finished, with an epoxy coating applied to protect the surface. However, beneath this protective layer, multiple cracks had developed in the concrete curbs surrounding the pad. These cracks were not superficial—they were structural, with widths ranging from 0.85 mm to 1 mm, exceeding durability limits for exposed concrete.
The cracks were concentrated around anchor bolts and power-actuated fasteners (PAFs), which are critical for securing the garage’s framing to the foundation. Their presence raised concerns about the long-term stability of the structure, especially under wind loads.
Anchor Bolt Placement and Curb Design
One of the primary causes of cracking was the improper placement of anchor bolts. Industry standards recommend a minimum edge distance of 4 to 5 inches from the center of the bolt to the curb edge. In this case, the measured distances were only 1.75 to 2.25 inches—far too close to the edge. This led to splitting cracks in the concrete curb, compromising its ability to resist tension and shear forces.
Additionally, the curb itself was only 6 inches wide, whereas an 8-inch width is typically recommended to prevent splitting. The reinforcement within the curb was also insufficient. Only one rebar was present at the bottom of curb and slab thickening, with a cross-sectional area of 100 mm², falling short of the minimum requirement of 131 mm². Engineering calculation suggests that 600 mm² of reinforcement would be ideal to resist splitting forces, which would require at least six 10M rebars.
Slope and Drainage Issues
Beyond cracking, the garage pad exhibited uneven slopes. Ideally, a garage pad should slope gently toward the entrance to facilitate drainage. In this case, the slope was reversed in some areas, causing water to accumulate near the garage door and along the sides. This not only poses a risk for moisture-related damage but also increases the potential for freeze-thaw cycles to affect the concrete’s integrity.
Correcting the slope would require either grinding down high spots or applying a leveling compound. However, grinding is not recommended, as it could reduce slab thickness and introduce new stress points. A specialized contractor should be consulted to apply a high-strength overlay that restores proper drainage without compromising structural performance.
Reinforcement and Thickness Concerns
Ground Penetrating Radar (GPR) scans revealed that the garage pad’s thickness varied across different areas, ranging from 2.9 to 6.6 inches. While some sections met the minimum thickness requirements, others fell short, particularly near the edges. These thinner areas are more susceptible to cracking under concentrated loads, such as shelving units or parked vehicles.
Reinforcement placement was also problematic. The steel rebars were located too deep within the slab, failing to meet CSA A23.1 standards for concrete cover and crack control. Without reinforcement in the top third of the slab, the concrete is vulnerable to shrinkage and heaving forces, especially in cold climates.
Durability and Lifespan Outlook
Despite the epoxy coating, which helps protect the surface from moisture and temperature changes, the garage pad remains at risk. The structural deficiencies in the curbs and slab could lead to further cracking, corrosion of reinforcement, and eventual failure of anchor systems. If left unaddressed, these issues may compromise the garage’s ability to resist wind uplift and lateral forces.
The expected lifespan of a concrete garage pad in cold climates is typically 15 to 25 years. However, without remediation, this particular pad may experience accelerated deterioration. Proactive repairs—such as reinforcing the curbs, correcting slope issues, and ensuring proper anchorage—can extend its service life and maintain structural safety.
Key Takeaways for Homeowners and Builders
- Anchor bolts must be properly spaced and placed to prevent splitting and ensure structural integrity.
- Concrete curbs require adequate width and reinforcement to resist tension and shear forces.
- Garage pads should be designed with proper slope to prevent water pooling and freeze-thaw damage.
- Reinforcement must be correctly positioned within the slab to control cracking and resist environmental stresses.
- Epoxy coatings protect surfaces but can conceal underlying issues—regular inspections are essential.
How Can AERZ Civil Structural Consulting Add Value to Your Project?
If you’re planning a home addition, renovation, or basement suite, and need expert support with:
- Structural engineering and drafting
- City of Calgary permit applications and plans drawings
- Construction support and field reviews
- Framing inspections
- Retaining and foundation walls as-built field reviews
- Assessment of reinforced concrete cracks
Reach out to us at Ashraf@AERZcivStrConsulting.ca or call (403) 708-3275.
Our team at AERZ Civil Structural Consulting Inc. is ready to help bring your next project to life with precision and care.
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