My contractor poured my patio in direct sun in July, and now it's spalling. Is this on them or bad luck?

This is almost certainly on your contractor. Pouring concrete in direct sun during Calgary's hot July weather without proper protection is a fundamental violation of concrete best practices and likely constitutes defective workmanship.

Why This Happened

Concrete poured in direct sunlight during hot weather (especially July in Calgary when temperatures can hit 30°C+) cures too rapidly on the surface while the interior remains plastic. This creates differential shrinkage that leads to surface scaling, spalling, and cracking. The rapid moisture loss from the surface prevents proper hydration of the cement, creating a weak, powdery surface layer that eventually flakes off.

Professional concrete contractors know that hot weather pours require specific precautions: scheduling pours for early morning or evening, using sunshades or tarps, continuous misting or wet curing, plastic sheeting, and sometimes admixtures to slow the cure. In Calgary's dry climate and intense summer sun at our altitude (1,048m above sea level), these precautions aren't optional—they're essential for a durable finish.

Your Legal Position

Under Alberta law, contractors have an implied warranty that their work will be performed in a workmanlike manner using accepted industry standards. The Alberta Building Code and CSA standards for concrete placement specifically address hot weather concreting requirements. A contractor who ignores these standards and delivers a defective product is liable for replacement costs.

Document everything: Take photos of the spalling, keep records of when the concrete was poured (date, weather conditions), and get a written assessment from another concrete contractor. Check Environment Canada's historical weather data for that day to confirm temperatures and conditions.

Next Steps

Contact your contractor immediately in writing (email creates a paper trail) describing the defect and requesting remediation. Give them a reasonable opportunity to assess and repair, but don't let them convince you this is "normal settling" or "cosmetic only"—spalling will worsen with freeze-thaw cycles.

If they refuse responsibility, you have options under Alberta's Prompt Payment and Construction Lien Act (PPCLA) and consumer protection laws. For disputes under $50,000, Alberta's Court of Justice small claims division handles construction defect cases. Document your damages (repair costs, inconvenience) and consider getting a professional assessment from a concrete specialist or engineer.

Prevention for Others

This is exactly why homeowners should verify their contractor's experience with concrete work and ask about their hot weather procedures before hiring. A professional should automatically explain their plan for temperature control, curing methods, and timing when scheduling summer concrete pours.

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