Not always , but in most cases, yes. A 12×12 shed is 144 sq ft, which exceeds the common 107 sq ft (10 m²) no-permit threshold used across most of Canada. Building codes are very regional in nature and even within provinces, codes in or out of city limits can vary greatly. Ontario is the notable exception the Ontario Building Code allows sheds up to 160 sq ft to be built without a permit, provided they are used only for storage. That means a 12×12 storage-only shed may not need a permit in Ontario but in most other provinces, it will. Always confirm with your local municipality before building.