Professional builders usually try to avoid pouring concrete footers in cold weather, but sometimes it is unavoidable. As we know, concrete is made with water, so how do these pros pour concrete when the weather is at or near freezing? Today, we will offer a few tips the professionals use to successfully pour concrete footers in cold weather.
Is it Okay to Pour Concrete Footers In Cold Weather?
As long as appropriate measures are taken, concrete footers (also known as footings) can be successfully poured in cold winter weather. However, pouring concrete footers in cold weather often involves site preparation, soil inspection, and adjustments to the concrete. These adjustments can include additives for specific purposes, pre-heating, blanketing, and specific concrete mixes. Using any of these methods will make pouring the footers easier, but using them in combination will provide the best results.
If the project will be larger than what can be mixed in a wheelbarrow, it’s a great idea to call ahead to a concrete supplier and tell them your plans. Some concrete manufacturing plants have the capability to use hot water and heated aggregate in the mixing to help the concrete cure. Concrete plants often have the ability to add accelerants such as calcium chloride also, which allows cooler concrete to cure like warmer concrete. Most concrete suppliers will be prepared for pouring in cold weather, so if these options are needed they will likely be available.
Will My Concrete Footers Be Weak If I Pour Them In Freezing Weather?
If no additional steps are taken, footers poured in freezing weather will often result in a weak foundation. There are other factors of course that can also impact the quality of the footers, such as too little portland cement or too much water in the concrete. However, many times pouring concrete in winter fails not because of the concrete, but the ground itself.
As we know, when water freezes, it expands. In the ground, when this water freezes it spreads out the soil around it as it expands, loosening the soil. Some may know this process as frost upheaval. The ground will remain in this state as long as it stays frozen, but when the ice thaws into water it will require less space. The soil will then compact under gravity and the process repeats.
Footers should always be poured only below the frost line for this reason. Soil that is subject to this constant freeze/thaw cycle is not suitable for footers because concrete requires a solid, stable surface or it will likely crack. Over the years builders have tried various methods of reinforcement to help resist the tendency of footers to crack, like adding rebar and fiberglass to the footers to help alleviate this problem.
How Do I Prepare For Pouring Concrete Footers in Cold Weather?
Professionals preparing for a cold weather concrete pour will usually plan the project well in advance. Advanced planning allows the pros to try and time the pour during a period of mild winter weather. Ideally, concrete should only be poured when the ambient air temperature is around 50 degrees fahrenheit or higher and expected to remain that way for a couple of weeks. To accomplish this, the pros will typically blanket the ground during a warmer period using concrete blankets, hay, or other form of insulator to retain the heat. Blanketing the ground helps it retain heat even when the ambient air temperature falls.
In regions that require even more heat retention, professionals may also incorporate tenting and supplemental heat. Tenting involves the use of tarps or builders plastic to capture supplemental heat around the footers in an effort to keep them above freezing. Often, portable propane heaters are then employed inside the tent to replace the heat that escapes the tenting. However, great care should be taken using this method, because these types of heaters use liquid propane and produce dangerous carbon monoxide that can become trapped inside the tent.
How Long Will Concrete Footers Take to Cure in Cold Weather?
The curing time required for concrete footers will vary based on the aggregate/cement/water ratio, but as a rule of thumb, concrete will typically cure in about five hours in summer as long as the temperature remains above 70 degrees or so. If the air temperature falls to closer to 50 degrees, the cure time approximately doubles to more like ten hours. In near freezing temperatures, the curing process can take a whole day.
As mentioned earlier, curing times can be manipulated to a limited extent by using additives, hot mixtures, and ground blanketing. In the most successful concrete footer pours, using all of these methods will significantly improve the chances of a successful pour. However, prudence should be exercised when the conditions are just too poor. If the ambient air temperature hovers at or close to freezing, often the best course of action is to delay the project until conditions improve.
