Converting an Existing Structure to Include a New ADU An existing single family residence is altered, to create a new ADU within the structure, for a total of two dwelling units. One units is owner occupied. Utilities: The entire structure may be served by one shared underground service lateral, from the utility's main to the structure, for water, sewer and natural gas. An accessible shut-off valve must be in place upstream of the gas meter, on the exterior of the structure. The water shut-off must be accessible to the occupants of both units. Electrical: A single shared electrical service, a single meter, and a single main service panel would be allowed, provided that (a) occupants of both dwelling units have equal and unrestricted access to the main electrical shut-off device, and provided further that (b) the capacity of the service panel shall be sufficient to safely handle the electrical loads attributed to two dwelling units, as determined by the electrical code in effect at the time application is made for permits relevant to the conversion. Plumbing: Both dwelling units may share common supply and waste plumbing systems and a common water heater appliance, so long as the occupants of both dwelling units have equal and unrestricted access to the water heater appliance. Heating: Both dwelling units may be provided their space heat by a shared, common forced air system (contrary to 1994 UMC 317.8) provided that (a) listed fire/smoke dampers are properly installed at all duct penetrations through all structural elements (walls, floor, ceiling, etc.) which separate the two dwelling units, and (b) listed carbon monoxide detector/alarm devices are installed in each of the dwelling units. Smoke Detectors: Smoke detectors shall be installed throughout both dwelling units in compliance with the code's requirements for new construction in effect as the time application is made for permits associated with the conversation. All detectors, in both dwelling units, shall be interconnected so that the activation of any one detector at any location anywhere within the entire structure shall also activate all other detectors, in both dwelling units, throughout the entire structure. Exiting: All components of the required exit systems in both dwelling units shall comply, as near as practicable, with code requirements in effect at the time application is made for permits associated with the conversion, especially with regard to egress windows in all rooms used for sleeping. Fire Separation: Listed fire separation assemblies are preferred where the code requires a "one-hour" separation between dwelling units. Listed assemblies shall be provided wherever the construction of walls or floor/ceiling assemblies is new, constructed during the conversion. Where existing walls and/or floor/ceiling assemblies compose part or all of the separation, Building Services Division will accept nominal 2" studs or joist, on regularly spaced centers, enclosed completely in 0.5" gypsum wall board or an equivalent lath and plaster. Doors in tenant separation walls may be either listed in 20-minute assemblies, or 1.75" thick solid-core tight fitting doors, equipped with a self-closing device and smoke gasketing material on both sides and the top of the door. Ceiling Height: The minimum ceiling height for ADU's located within existing structures shall be 7'.
