Know your Frost line

Over the years, I have had many friends and relatives ask me about frost line depth in the Madison area since adding the fireplace and the pergola to our back patio. Since they want to do similar things in their back yard, they asked me when all they would have had to do was Google it themselves, but I get it.  We’re standing on the patio near a roaring fire drinking a beer and the conversation comes up.  

I did the research when building the fireplace because I did not want the fireplace to move even a fraction of an inch so knowing the frost line was a pretty important thing to know. I have to add though that it’s not an exact science because, you know, it’s weather-related and that is not completely dependable, but it’s close enough for our purposes. Going deeper than the frost line is a no brainer because there’s no going back once you start to pour the cement footings.

When I tell my friends that the frost line is around 60″ they freak out and can’t believe it’ that deep. I’m always stunned by their reaction. If they didn’t know the number then why does 60″ freak them out? And, why would I lie about that? Trust me, the number is 60″.

When water changes from a liquid to a solid it expands 9% in volume. That’s quite a bit and it will affect footings and foundations. This is why water and sewer pipes need to be buried below the frost line. I know this seems pretty basic but many DIY’ers have the wrong information when starting any projects related to footings and frost line depth. When it comes to repairing the foundation one must go to to get experts to have a look at the problem.

The attached chart above is a national chart of frost line measurements for the continental USA but your local government codes will be even more accurate. Knowing what the frost line numbers are will affects the winter freeze and move objects up as the water solidifies. When the water thaws it doesn’t thaw evenly and therefore stationary objects become out of plum or square. This is called frost heave. This is why your cement driveway cracks and cement steps become strange looking. It’s why your basement floor will heave up and crack. Ugh!  The worst! If you want to find out more about the solution to this problem, you need to get in touch with experts.

The numbers can be small but if this continues year after year your deck, fireplace or any footing supported project is going to be noticeably out of square and can even become dangerous.

So, know the frost line before you begin your next outdoor project and then go deeper. You’ll thank me later.