Will Frost Heaving Damage My Home’s Foundation in South Carolina?Nov 5, 2017
As the premier foundation repair company, located in South Carolina, CNT is often called upon to explain how the winter months can damage your home’s foundation. While we are treated to relatively mild winters in South Carolina, do not be lulled into a false sense of security assuming that your home is free from winter’s harm. In this article, we will discuss frost heave, the element needed for frost heave, the ways in which frost heave can be controlled, and distinguishing between frost heave and foundation settlement.
Can Frost Heave Harm My Home’s Foundation in South Carolina?
Of the myriad types of damage that may visit your home’s foundation this winter, frost heave can be one of the most detrimental. Frost heave occurs when freezing temperatures penetrate the ground, causing subsurface water to form ice structures that displace the soil along with anything that rests on or in it. While it was once thought that frost heave occurs because water expands as it freezes, the process is actually more complicated, involving not only expansion due to freezing but also the accumulation of additional layers of ice as water is drawn up from below the frost line. The depth to which freezing temperatures penetrate the ground is referred to as the freezing plane or frost front
When freezing temperatures penetrate the ground, water trapped in voids in the soil forms ice crystals along the frost front. As it solidifies, the water expands by about 9%. Additionally, the freezing process dries the surrounding soil, drawing unfrozen water from below the frost front through capillary action and vapor diffusion. This water freezes to the ice crystals that have formed, thickening it to create an ice lens.
The conventional approach to the design of foundations to prevent frost damage is to place the foundation beyond the depth of expected maximum frost penetration so that the soil beneath the bearing surface will not freeze. This measure alone does not necessarily prevent frost damage; if the excavation is backfilled with frost-susceptible soil it may lead to damage from adfreezing. Adfreezing is the process by which two objects are bonded together by the ice that has formed between them. The stress required to separate an object from the frozen ground is frequently referred to as the “tangential adfreeze strength.”
What Elements Are Needed for Frost Heave in South Carolina?
There are three elements are necessary for frost heave:
- Frost susceptible soil
- Subfreezing temperatures
Remove any of the three elements and frost heaving will be eliminated or at least minimized.
Additional factors which will affect the degree of frost heave:
- Rate of heat removal
- Temperature gradient
- Mobility of water and permeability of soil
- Depth of water table
- Soil type and condition (e.g., density, texture, structure, etc.)
What are the Ways in Which Frost Heave Can Be Controlled in South Carolina?
There are several ways in which you can manage frost heave:
Footings and Piers. Code mandates that support structures either extend below the local frost line or be protected by insulation so that the bearing soil is not subject to freezing and, thus, heaving. Frost heave also can be controlled by backfilling around piers with gravel to promote drainage, using a sleeve to prevent ice from gripping the concrete and pouring footing bases that resist upward movement. Clean sand and gravel are commonly used for bases under floor slabs and pavement. The sand and gravel provide some insulating value but usually not enough to adequately reduce frost penetration.
Driveways, walkways, and patios. The occurrence of frost heave can be minimized by replacing fine-grain, frost-susceptible soil with coarse granular material that is not subject to heaving. Drainage measures can reduce the presence of moisture, which also prevents heaving. Providing a capillary break is another option; interrupting the capillary action that draws water toward the ice lenses can make frost heave less severe.
Basements. Frost heave can seriously damage a basement if the ground surrounding that basement freezes to the foundation walls. When this happens, heaving soil around the house can carry the walls with it. This situation does not occur with heated basements because a heated basement, insulated or not, loses heat to the soil surrounding it. This outward heat loss pulls moisture away from the foundation walls.
Although it may not seem like a winter priority, basements should be winterized by first waterproofing the basement. During warmer weather, water in the basement can cause insulation and framing to mold and rot, necessitating replacement at some point. When temperatures drop below freezing, water turns into ice, and expanding ice can cause cracks in basement walls. Waterproofing eliminates these potential problems and ensures that the area remains warm and dry throughout the year.
Additional projects recommended for getting your basement winter-ready include:
- Install double-paned replacement windows, replacing any existing drafty windows.
- Make sure that exterior doors are properly weather-stripped.
- All exterior protrusions (pipes, ductwork, etc.) should be thoroughly inspected and properly insulated with an expanding foam or similar product.
- Basement walls can be insulated by framing and moisture-proof backer board. Fiberglass insulation is not recommended unless there is no chance of water or moisture forming on the walls. Fiberglass insulation is susceptible to mold.
- Floors should be insulated with dead air space. With some framing and plywood, an insulating dead air space is created between the concrete floor and the basement floor. Keep in mind that this should only be done if you have a completely waterproof basement.
- If your basement is dry or has a dehumidifier, insulating the basement ceiling with rolled fiberglass insulation is recommended.
What is the Difference Between Frost Heave and Foundation Settlement in South Carolina?
It can be difficult to distinguish between frost heave and settlement. since both types of movement can cause similar cracking in a foundation.
Evidence suggesting frost heaved cracks in a home’s foundation:
- Evidence of cyclical movement in poured concrete foundations such as crumbling broken edges of cracked sections may suggest recurrent movement.
- Evidence of a history of the site or building water entry or poor site drainage may suggest frost heaved damage to a poured concrete floor slab.
- The absence of evidence of backfill or site fill problems at a poured concrete structure: a garage slab poured at grade and cracked across its width near the entry is more likely due to frost heaves. However, this basic principle of diagnostics – absence of evidence is not evidence of absence.
Evidence suggesting settlement cracks in a home’s foundation:
- Evidence of probable backfill or infill defects below a poured concrete slab shows cracks in a garage floor slab that are not near nor tracking the footing across the garage entry, especially where the level of the garage floor is well above outside grade – fill was needed inside the garage foundation.
- Evidence of extensive poured concrete slab settlement such as noting that the level of the top of the slab is below a concrete trace line along the foundation walls, where the top was located when the slab was originally poured is clear evidence of slab settlement.
Beit cold in the winter or heat in the summer, your home’s foundation takes a beating year round. However, with preventative measures, our seasonal temperatures and weather extremes can have less an effect on one of your largest investments. Over time, without proper maintenance, a foundation will become susceptible to freezing around the foundation and the proper winterizing steps can help avoid a significant problem for the foundation. To learn more about winterizing your home, please refer to our article entitled, “ How To Winterize Your Foundation To Prevent Damage in South Carolina.”
To help ensure the health of your home’s foundation this winter, call CNT to schedule a free winterization estimate. Your home is too valuable to be left to chance this winter.