Does a cottage addition built on a concrete block basement need to be heated to prevent damage from freezing?
Any time soil and concrete live beside one another there is a possibility of foundation damage during a freeze. Soil deeper than about two metres naturally maintains a temperature of 9°C even in winter. When basements are not properly insulated or heated, warmth from the soil can be transferred into the colder building. In the simplest of terms, this heat loss allows the water in the soil to freeze, thereby creating pressure that can bow your foundation inward or heave the entire structure upward. The process can cause cracks or greater damage. Some soils are less susceptible to freezing or frost-heaving, but earth containing fine sand or silt is more of a risk.
Ensuring your basement is above 5°C will reduce the likelihood of frost damage, not to mention help keep basement materials drier, reducing the potential for unpleasant odour and mould. Simply heating the basement may not be the most efficient solution. It may be cheaper in the long run to stem the heat transfer through the basement wall by covering the exterior of a block foundation with thermal insulation, such as Styrofoam.