Q. After a long process, our house plans are finally approved, and we want to get going right away. It took months to get plans and almost a year to get them approved. We got a zoning variance and had to show an architectural review board samples and colors of the outside materials we chose. It seemed to take forever. Our contractor says he can start in a few weeks, but warned that the weather may not be good for starting the concrete foundation with our high water table. Others told us we could use “anti-freeze” to keep going, but the contractor we picked is not recommending it. What do you recommend?
A.Weather is a huge factor in construction. Temperature, humidity, wind, barometric pressure and precipitation can make all that plan preparation and government scrutiny seem minor when compared with damage, both internal and external, to the building. Parking lot paving comes to a standstill when the ground is too cold, and potholes in roadways are partially the result of weaknesses from water and temperature attacking the asphalt, stretching, compressing and breaking it, like taffy, under constantly changing loads and atmospheric conditions.
Concrete is often thought to be very strong, resistant to water, able to just sit there and do the job of holding things up or holding things back. But it does none of those things very well if it isn’t the right recipe and thicknesses, augmented by an internal spine of steel, fibers or additives that make it water-resistant and stronger or give it just the right amount of flexibility. Concrete, like asphalt (and all materials), isn’t static, just sitting there. It’s dynamic, expanding, contracting, shrinking and enlarging. Pour cement right before a major weather chaange and the consequences can be immediate failure, or something that isn’t noticed until the rest of the building is sitting on top. Small cracks at the beginning can signal future catastrophic results.
The process of concrete setting up is often thought of as “drying,” but actually, concrete “cures” from internal chemical reactions and external atmospheric influence. Too hot, too cold, too wet or dry and the concrete cure can be changed or ruined. The chemical reaction can even be stopped by adding sugar, of all things.
Unless the weather remains fairly stable, between at least 45 and 55 degrees for three weeks, to allow the concrete to cure best, I think you should listen to your contractor. It’s rare to hear that a contractor doesn’t want to get started right away, and I admire and respect the good advice you’ve been given. If frost develops while the cement is still curing, expanded water crystals will cause tiny internal breaks that can’t be easily fixed. Additives like calcium chloride are referred to as “anti-freeze,” but studies show that the concrete may not reach the strength required. I recommend waiting if the weather remains wet or uncertain, especially above a high water table. Happy Holidays!
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