Asked by: Codruta Kozak
asked in category: General Last Updated: 31st January, 2020

Why are footings under the frost line?

When you excavate your footings you will need to dig below the frost line. This is the depth at which the moisture present in the soil is expected to freeze. Once your footings are buried below the frost line the ground will act as a barrier to insulate the soil below the footing from freezing in the winter.

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Hereof, why must building footings extend below the frost line?

Dig and pour your deck footings so they extend below the frost line. That way, they won't move, or heave, as the ground freezes and thaws during seasonal changes.

One may also ask, is frost depth top or bottom of footing? If the frost depth is 36 inches the bottom of the footing needs to be below the 36 inches, not the top not some point between the top and the bottom only the bottom. Frost has to be able to get below the bottom of the footing before it may cause an issue.

Keeping this in consideration, why is foundation below frost line?

Building codes sometimes take frost depth into account because of frost heaving which can damage buildings by moving their foundations. Foundations are normally built below the frost depth for this reason. Water and sewage pipes are normally buried below the frost line to prevent them from freezing.

What happens if you don't go below the frost line?

If you don't dig below the frost line, you run the risk of seasonal shifting and structural damage. Pouring a post-hole footing requires very little in the way of tools and materials.

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