Yes — concrete CAN be poured in winter in Ottawa, but the cost premium, required protection measures, and risk profile change dramatically below 5°C. This guide covers exactly when winter pours make sense, the cold-weather concrete protocols required by CSA A23.1, what contractors charge for winter premiums, and the projects where waiting for spring is genuinely the better choice.
CSA A23.1 (the Canadian standard for concrete) classifies any pour where air temperature is below 5°C as 'cold weather concrete' — triggering specific protection requirements. Pours below -5°C require additional heating and accelerator measures. Pours below -15°C are generally not recommended for residential work. Ottawa averages -10°C in January with -25°C cold snaps, so virtually all December-March pours fall into the cold-weather category. The concrete must reach 5°C+ during curing for 3-7 da...
Hot water in the mix (concrete plant heats water to 60-70°C). Accelerator admixtures (typically non-chloride accelerators like calcium nitrate to avoid corrosion). Heated aggregates at the plant. Insulated concrete blankets (R-3+ values) covering all surfaces for 3-7 days post-pour. Hoarding (temporary enclosure) with propane or electric heaters for slabs over 50 m² or for foundation walls. Ground thawing if the soil below the pour is frozen — required for footings and slab-on-grade work. Each m...
Standard 32 MPa concrete in summer: $338-$365/m³ delivered. Winter premium: +$30-$50/m³ (about 10-15% on materials). Hoarding rental: $400-$1,200 for residential-scale jobs. Heater rental + propane: $200-$600 for a typical 3-7 day cure period. Insulated blanket rental: $1.50-$3.00/m² per week. Frozen ground excavation surcharge (when applicable): +30-50% on the excavation portion. Total winter cost premium on a typical residential project: 25-50% above summer pricing.
Time-sensitive foundations for builders working through the spring/summer build cycle. Emergency repairs to failing foundation walls or footings. Slab-on-grade work in heated structures (inside a sealed garage with active heating). Small driveway or sidewalk repairs that are accessible and easy to protect. Commercial projects with strict timelines. For these categories, the premium is justified by schedule preservation.
Driveways and walkways without time pressure — winter pours have higher long-term risk of surface scaling and freeze-thaw damage even when done correctly. Decorative concrete (stamped, exposed aggregate, coloured) — finish quality is harder to control in cold conditions. Large patios — protecting a large surface area with hoarding and heating becomes economically prohibitive. Pools and outdoor structures that won't be used until summer anyway. For these projects, save 25-50% and wait for late Ap...
Not all concrete contractors handle cold-weather work competently. Vetting questions: (1) Walk me through your cold-weather protocol — they should reference CSA A23.1 specifically. (2) What admixture do you use and why? (3) How long will the blankets stay on? (4) Will you have a hoarding/heating plan documented? (5) Can I see references from winter pours from the last 2-3 years that I can inspect this spring? (6) What's your warranty on winter work — most reputable Ottawa contractors offer the s...
Below -15°C is generally too cold for residential concrete work. Between -5°C and 5°C, cold-weather protocols are required (heated water, accelerators, blankets, hoarding). Below -5°C, additional heating measures are required and costs rise sharply.
Typically 25-50% above standard summer pricing in Ottawa. The premium comes from heated water and aggregates, accelerator admixtures, insulated blankets, hoarding rental, heater rental and fuel, and frozen ground excavation surcharges.
When done correctly per CSA A23.1, yes — the long-term durability is comparable. When corners are cut (no blankets, no accelerator, insufficient protection time), winter pours suffer from surface scaling, micro-cracking, and reduced freeze-thaw resistance. Contractor competence matters more than season.