Winter brings freezing weather, and with it, the potential for frost heave – a phenomenon in which frozen ground shifts and expands. Houses that are not properly designed to handle the effects of frost heave could require costly repairs and even replacements of damaged structural elements. Here is everything you need to know about frost heave and ways that builders can combat it.
Defining frost heave
When the ground freezes, ice crystals in the soil expand, forcing the dirt somewhere else. Usually, the only direction for that soil to go is up, resulting in a massive displacement of earth that can wreak havoc on a landscape. Structures without the proper footing to anchor it can be shifted and even structurally compromised. Frost heave can affect porches, decks, overhangs and even the foundations of a home.
Such soil displacement is a serious concern: Frost heave and expansive soils are among the most damaging natural hazards to manmade structures in the U.S., according to the Virginia Department of Mines, Minerals and Energy. While human health is not normally at risk, frost heave can result in costly repairs, as well as a poorly functioning house. Shifts in the earth can cause doors to jam, warped flooring and even broken foundations.
Areas most affected by frost heave
The phenomenon is most common during extended bouts of cold when temperatures dip below freezing. Soil quality can also affect the magnitude of frost heave. Expansive soils are determined by the presence of clay minerals, and their effects can be magnified by drought followed by precipitation.
Different parts of a home are more susceptible to frost heave. Areas with lighter loads, such as porches and patios, are more sensitive to frost heave, while heavier locations, such as the ground beneath a fireplace, are more resistant.
Many craftsman house plans offer walk-out basements, porches, side-steps and decks. HHF -7779 is a good example of a home with many elements susceptible to frost heave. In addition to two extended porches on either side of the house, the ground slopes away to reveal a walk-out basement. The foundation there, as well as the one-story posts that hold up the back porch would require special attention to protect against frost heave. Fortunately, it is easy to plan ahead and minimize any risks of structural damage.
Protecting against frost heave
Builders can combat the effects of frost heave by making sure that T-footings are sunk sufficiently below the frost line. That line can change depending on soil type, region, climate and ground moisture. Builders should research local regulations and make sure that they take into account the specific soil type and climate of the site.
T-footings are much better designed to resist the effects of frost heave than a slab-on-grade foundation. However, you can still pour slab-on-grade if you use insulation along the perimeter of the house, set up both vertically and horizontally to protect against frost heave, according to ConcreteNetwork.com. For walk-out basements, insulation can be more cost effective than excavating and pouring slabs.