Frost-Protected Foundation
This pattern is shaped by
Problem
In cold climates, conventional foundations must extend below the frost line — often 1.5 to 2 meters deep — to prevent frost heave. This makes small buildings (sheds, greenhouses, laneway houses) disproportionately expensive to build, because the foundation costs the same regardless of what sits on it.
Evidence and Discussion
Frost-protected shallow foundations (FPSFs) use horizontal insulation extending outward from the building perimeter to keep the frost line above the footing level. This allows foundations as shallow as 300mm even in Edmonton's climate. The technique is standard in Scandinavia (used in over a million buildings in Norway and Sweden) and accepted by the Canadian building code.
Therefore
for any small building on a cold-climate property — garden office, greenhouse, workshop, laneway house — use a frost-protected shallow foundation rather than a deep footing. Extend rigid insulation (EPS or XPS) horizontally at least 1.2 meters from the building perimeter at or near grade. This reduces excavation, concrete, and cost by 30–50% while providing the same protection against frost heave. The savings make small outbuildings financially viable — which is what makes patterns like THE FIFTEEN-MINUTE SHED (6) and THE LANEWAY HOUSE (13) practical.