I am going to be building a small detatched garage next to my house. The guy who is pouring the foundation for me wants to get started this month, but winter is here in the NW and the ground is covered with snow. Is it okay to pour cement in the cold? What about the frozen ground? Should I proceed?
Bill Whitefish - MT
Bill, although you can pour a concrete foundation in just about any weather conditions, there are several issues that need to be addressed before you proceed with a cold weather pour. Most importantly, the ground beneath the building site needs to be completely thawed before you begin digging. Pouring a slab foundation on top of frost or frozen dirt can cause moisture to become trapped under your foundation, which might ultimately lead to frost heaves that crack your slab. Likewise, digging and properly preparing the ground can be down right impossible when the ground is frozen.
The most effective way to thaw the ground under a building site is to use a ground heater and insulating blankets. A ground heater is a large machine that continuously heats and pumps glycol through a closed loop of hose, which is spread out over the building site and then covered with insulating blankets. You may have to run the ground heater for 1-4 days, depending on the specific conditions at your site.
Once the ground is thawed, you can then prepare the site and set up your foundation forms. To keep the ground from re-freezing, you should keep the site covered with insulating blankets and possibly even tent the site so that regular construction heaters can be used during and after the pour. You can use plastic sheeting and some scaffolding to erect the temporary shelter around the building site.
Heating, insulating, and protecting your building site is important, but keep in mind that some of the most important considerations for a cold weather pour are in the hands of the batch plant where the concrete will be delivered from. Factors such as water temperature, mix ratios, and the use of curing accelerators are all crucial to a successful pour. As the homeowner, you need to make sure that there is good line a communication between yourself, the concrete contractor, and the batch plant, because there is little room for error when pouring a concrete foundation in the winter.