Every home is lived in on two levels at once. On the surface are the rooms where daily life unfolds: the counters where meals come together, the showers that start each morning, the patios and yards where families gather. Beneath and around them sits the structure that makes those rooms possible, from framing and foundation to the outer shell, the mechanical systems, and the buried infrastructure that carries wastewater away. The two levels depend on each other completely. A beautiful room built over rotting framing will not last, and a sound structure filled with cramped, worn spaces never feels like…