6" below grade
They are located below the frost line
The frost depth level below area's usually not less than 800 mm .
The frost line depth for the Ottawa-Montreal area ranges from 1.4m to 1.5m below surface elevation.
A concrete foot generally must extend one foot below the frost line. in some cases it may have to be more or less.
5.6 feet below ground level.
Depends on what you plan to put ON the footer. If a building- yes. Above the frost line, when the soil freezes it will push the foundation up- but not evenly.
the maximum depth of ground below which the soil does not freeze in winter.
In Pennsylvania, the frost line depth can vary based on location, but typically ranges from 36 to 42 inches deep. To install a mailbox post below the frost line, you would need to dig a hole at least 3-4 feet deep to ensure the post remains stable during freezing and thawing cycles.
Average is 4ft, building code requires water pipes to be at least 6ft deep to be well below frost line and safe from frezzing.
A frost proof toilet the trap is located below the frost line
If you didn't, they could freeze in the winter and burst.