Frost heave affects foundations in areas where it gets cold enough for the soil to freeze, so not every home is at risk. Soil movement from the freeze and thaw cycles puts stress on a foundation, causing it to move or crack.
Frost heave is primarily a problem for slab and pier foundations. Basement foundation walls can also suffer from frost heave, although it’s rarer, as these foundations typically penetrate below the frost line.
Read on to learn what you should understand about frost heave damage.
How It Happens
There’s more to frost heave than cold temperatures. Certain other conditions must also be present in order for soil movement to affect the foundation.
Soil Type : Not all soils heave in cold weather. Coarse, sandy, or gravelly soils don’t absorb moisture well, so they aren’t susceptible to frost heave. Clay and fine sand soils, though, can suffer from heaving, as they are more prone to holding moisture that can freeze and expand outward.
Drainage : There must be water present for frost heave to occur. Freezing temperatures won’t cause heave if there is no moisture in the soil, so the presence of drainage around the foundation will minimize heave concerns. Areas with dry climates and little surface moisture in the soil also tend to be resilient to frost heave.
Foundation Features : Foundations with footings that are deep enough to extend well past the frost line are less likely to heave, as are those poured so they are wider at the bottom than they are at the top. The wider bottom width is especially important for post foundations, as they can easily be pushed up by the freeze-thaw cycle if the bottom of the post is narrower than the top.
How It Appears
There are visual clues that frost heave is occurring, but how visible they are may depend upon other features in your home. You may not notice the damage unless you are having other work done, such as the carpets over a slab foundation replaced.
Bulging floors : One of the more obvious types of foundation damage from heave is the floor bulge. The area affected most by the upward movement from the heave will bulge upward, resulting in an uneven floor that is noticeable even below carpeting. Bulges may be localized to one area if only one pier is suffering heave damage.
Floor and Wall Cracks : Floor cracks are often one of the first types of damage, but they are often hidden beneath floor coverings. You may notice them when replacing carpeting or linoleum, or if the crack transfers through and causes tile flooring to crack as well. There may also be some wall cracks, particularly near lower corners where pressure from the moving foundation is stressing the wall junction.
Wall Bowing : Sometimes basement walls begin to bow inward in response to the inward pressure being exerted by frost heave movement on the upper part of the foundation wall. Cracks may form as well, or you may notice buckling in the plaster of a finished wall. Keep in mind there are other structural issues that can cause bowing, so always schedule an inspection to verify the cause.
How to Prevent It
Prevention is possible in areas where frost heave is a concern. Most preventative tactics are done at the time of home construction.
Foundation Depth : Pouring the foundation so it extends below the frost line is the single best method to ensure frost heave damages never occur. Your builder must check local records to determine the frost line on your property so that the proper foundation depth can be determined.
Proper Backfill : During construction, as mentioned previously, it’s important to use coarse-grained soil as backfill. The dept of this backfill should extend below the frost line in the soil in order to be most effective.
Drainage Installation : Installing drains around the foundation can be done at any time during or after construction, making it one of the preventative tactics that can be implemented after minor frost heave has been noticed.
How to Repair It
Fortunately, most damages from frost heave can be repaired, especially if you address them before they become too severe.
Foundation Pier Installation : nstalling extended piers beneath your current foundation can prevent heave from moving the foundation anymore. Extended piers are used on both slab and pier foundations. These new piers are poured underneath stress points suffering from heave. The new pier will extend below the frost line, thus preventing movement in the future.
Soil Stabilization : If the issue is with the soil quality near the foundation, then having the heave-prone soil removed can help greatly. Your foundation contractor will then backfill in a replacement soil that is less prone to frost heave problems. This may be done in conjunction with extended pier installation since the foundation must be excavated for both types of repair.
Foundation Leveling : In cases where the foundation is badly out of level due to previous heave damage, some leveling may be needed before other repairs commence. In some cases, this may mean excavating under a raised area so it can be brought down to level again. In other cases, a mudjacking method that injects a soil slurry or a polyurethane foam may be used to bring up the lower parts of the foundation to level.
Contact Straight Line Construction if you have concerns about the effects of frost heave on your foundation.