When to Use a Frost Wall

Importance

• Frost walls aren't free-standing walls separate from the home, but rather an extension of the walls of the foundation. Depending on the area, the soil more than a few feet from the surface won't freeze. Setting the bottom of the foundation lower than the freezing depth, known as the grade, with a frost wall helps prevent damage to the foundation. Soil shifts when it freezes and having frozen soil below the foundation causes serious cracks.

Usage

• Any homes built where the soil freezes below a few inches from the surface need some kind of frost wall for protection of the foundation. When the grade is only 1 or 2 feet, you may be able to dig out the whole foundation to that level and prevent using extra frost walls, according to the Natural Home Building Source. Using frost walls that only extend to full depth around the edges of the foundation saves time when you need to dig down 4 or 6 feet.

When Not to Use Them

• If the ground doesn't ever freeze, there's no point in digging and pouring a frost wall. However, even if you live in a very cold environment, the ground below your planned foundation has a big effect on whether or not you need a frost wall. Solid or broken slabs of bedrock and deep beds of gravel won't expand when frost hits, so there's no frost wall needed for foundations built over these materials, according to the Structural Engineers Association International. The bed of rock must be very deep, not just a few inches over soil.

Alternatives

• Building on the surface of properly compacted soil is much less expensive due to the reduced need to dig deep. This building method was once restricted only to warm climates, but recent advances in material technology now allows cold climate homeowners to use it as well. Insulating foam with a high strength rating is used under and around the foundation, according to Oikos. The insulation prevents frost heaving from damaging the slab as long as proper drainage systems are installed with it to keep the soil dry.