We fielded a query from a returning Calgary resident the other day. We were discussing the feasibility of an extension to their home when the subject of northern climate foundations cropped up.
“Why do we have such deep complicated foundations in Calgary, when South Africans and Australians have simpler, shallower slabs,” they demanded. Fortunately we understand the difference climate makes and were able to explain how it works.
Northern Climate Foundations are Sensitive to Frost Lines
The ground never freezes below the surface in southern hemisphere climates, with the exception of high altitudes, and near-polar regions. However in places like Calgary the ground regularly freezes in winter to quite a depth.
The actual freezing depth to where the ice liquefies depends on adjacent materials and any nearby heat sources. However, in Arctic and Antarctic locations the frost line reaches so deep it becomes year-round permafrost.
Building codes generally recommend building foundations below the local frost line if there is likely to be one. That’s because frost heaving can damage a shallower structure as ice forms and expands, supplying upward pressure in the process. This gives rise to the more complicated northern climate foundations the returning resident questioned.
How Deep Does the Calgary Frost Line Reach?
The frost line in Calgary typically reaches an average seven feet down. This usually takes several months with maximum depth achieved in late February / early March. However, if we have an unusually cold autumn, it may reach deeper down before spring returns.
Two Ways to Protect Foundations against Frost
Constructing seven-foot and deeper foundations is expensive, although that has long been the traditional approach. Many builders prefer to dig slightly deeper and create basements footed below the frost line instead.
However, this is an energy-intensive solution and we need to find greener options for the sake of our planet. That’s why shallower concrete slabs encased in insulating polystyrene sheets are steadily catching on.
This system is also a possibility when erecting unheated buildings. However, this is not a permanent solution because polystyrene is not a renewable material. Hence Calgary may have more complicated northern climate foundations for years to come still.
Contact Valiant Solutions if you would like to know more about this intriguing topic.