# Can I lay concrete in cold weather?

Yes, you can lay concrete in cold weather, and it costs more preparation than money. Order a warmer mix, never place on frozen ground, have insulated blankets on site before the truck arrives, and plan for a longer protection period. If the schedule can move, waiting for spring is cheaper.

## Short version

- Cold-weather work is normal work with three extra jobs: warm the mix, warm the ground, and keep the heat in afterward.
- Never place concrete on frozen subgrade — thaw it first and keep it thawed.
- Blankets, straw, or an enclosure go on site before the pour, not after somebody notices the forecast.
- Everything runs late: set time, finishing, form stripping, and the day you can drive on it.
- Decorative, colored, or stamped work is the first thing to postpone.

## What has to be ready before the truck arrives?

The ground comes first. Concrete placed on frozen subgrade sits on a surface that will thaw, settle, and drop the slab with it, and the frozen ground pulls heat out of the mix from below while it does. Thaw it with blankets, hydronic heat, or an enclosure, and keep it thawed until the pour. Forms, reinforcement, and any embedded steel should be free of snow, ice, and frost — steel at 20 °F chills the concrete around it immediately.

Protection materials belong on site the day before. Insulating blankets, poly sheeting, and straw are useless in the truck when the finishers are done at dusk and the temperature is falling. Order more than you think you need, because edges and corners lose heat from two directions and need doubling up.

Schedule the pour for early in the day. You want the concrete placed and finished while air temperature is at its highest and the crew is not fighting darkness, since cold weather stretches the wait between placing and finishing by hours.

## What will the ready-mix supplier do, and what won't they?

Suppliers control the concrete's temperature at delivery, and that is the main service they sell in winter. Heated mixing water is the usual method, sometimes with heated aggregates, and the plant adjusts the mix to hit the delivery temperatures CIP 27 specifies by section thickness — 55 °F (13 °C) for anything under 12 inches, which covers residential flatwork. Accelerating admixtures, extra cement, or a Type III high-early-strength cement are the other levers.

These are ordering decisions, not jobsite decisions. NRMCA CIP 31 makes the point that placement conditions and requirements should be discussed with the supplier when the order is placed. Cold-weather services, minimum loads, and any winter surcharge are set by individual companies with no national standard, so ask what is included before the day of the pour.

What no supplier does is protect the slab after the chute. Once it is placed, temperature control is the contractor's or homeowner's responsibility, and that is where most cold-weather failures actually happen.

## How do you protect the slab after finishing?

Insulating blankets are the standard answer for flatwork. They trap the heat the concrete generates as it hydrates, which is what keeps the reaction going when the air will not. Lap the seams, weight the edges, and extend coverage a foot past the slab on every side. Straw over polyethylene works as a substitute, and rigid foam board is worth it over exposed edges and corners.

Enclosures with heaters are the next step up for walls, footings, and any pour that has to keep running through a hard freeze. ACI 306 covers heated enclosures, including how they must be ventilated — unvented combustion heaters raise carbon dioxide inside the enclosure and can damage a fresh slab surface.

Take protection off gradually. CIP 27 limits the temperature difference between the concrete surface and its interior to 35 °F (20 °C), because pulling blankets off a warm slab into cold air cracks the surface it just protected. Peel back in stages over a day rather than stripping everything at once.

## How much longer does the whole job take?

Plan for roughly double the waiting at every stage, and treat all published timelines as warm-weather timelines. Cold slows hydration, so bleeding, set, and the finishing window all stretch; forms stay on longer; and the day you can walk or drive on it moves out.

Test rather than guess. Field-cured cylinders made under ASTM C31 and kept next to the slab, under the same blankets, tell you what the slab itself has done, unlike lab-cured cylinders which tell you what the mix is capable of. On larger jobs the maturity method in CIP 39 does the same thing with temperature sensors, estimating in-place strength from the slab's actual temperature history.

The strength milestones the protection period is built around are covered in [how cold you can pour concrete](/questions/weather-hot-and-cold/how-cold-can-you-pour-concrete/) — protect until the concrete reaches them, not until a calendar date passes.

## When should you just wait for spring?

Wait if you cannot commit to the protection. The equipment list is short but not optional: enough blankets to cover the pour plus overlap, a thawed subgrade, and someone checking the slab morning and night for the first several days. If any of those is missing, the slab is being poured on hope.

Wait also for anything decorative. Stamped, colored, exposed-aggregate, and broom-finished work all depend on hitting a finishing window that cold weather moves unpredictably, and color problems from cold placement do not sand out. Sealers have their own minimum application temperatures on the data sheet.

The honest cost comparison is worth running. Blankets, heat, extra admixture, and the extra crew hours often exceed what the delay costs, especially for a patio or a walkway that nobody is waiting on. A footing that has to be poured for a framing schedule is a different calculation than a garden path.

## Common mistakes

- **Placing on frozen ground** — the subgrade thaws, the slab settles into the void, and the crack shows up the following spring.
- **Ordering the concrete before ordering the protection** — blankets that arrive after the finishers leave protect nothing.
- **Stripping blankets all at once** — a 35 °F swing between surface and interior is the limit CIP 27 gives, and exceeding it cracks the surface.
- **Judging strength by the calendar** — field-cured cylinders or a maturity meter tell you what the slab actually did in the cold.
- **Pouring decorative work in the cold** — the finishing window moves, and color and stamping problems are permanent.