A permanent frost protected shallow foundation footing for a building is assembled from a plurality of form parts arranged in a chain that is partially below ground level to form a foundation perimeter. The form parts are made of a lightweight material such as insulating foam material shaped as an elongated sectional unit with an overhang part overhanging a cavity part of an interior cavity. The interior cavity has an opening for receiving a concrete pour concurrent with a concrete pour of a floor. Open ends of the assembled sectional units abut each other in end-to-end alignment to form an elongated cavity inside the perimeter chain of form parts that is filled with concrete. The overhang part may have a foot shape that fits inside the interior cavity of another form part that may also have a foot shape for compact storage or transport prior to assembly.