Once the excavation was complete, Maine requires a footer be at least 4’ below grade to protect against frost/freezing during the winter. This depth varies around the country. For instance, our safe home in North Carolina only required an 18” depth. And in Texas, we are told they merely scrap the top layer to remove the organics.
Special attention was required for the conduit pipes between the utility building and the main house. The pipes carrying water (radiant pex and domestic) were put at the lowest, 4’ below grade. The pipes carrying electrical wire and a spare, were placed at 3’ below grade. Gravel was placed around all pipes and then sand. A 3 sided trapezoid covering the conduits was built using 2” EPS Rigid Foam board, 2’ high along the sides and 8’ wide across the top extending 4’ either side of the 2’ vertical boards. Sand was placed over this Rigid Foam board configuration to grade. These additional measures were taken to ensure that the frost did not penetrate through the pipes and freeze the water moving between the utility building and the house.