A 793 sq ft attached Accessory Dwelling Unit in Fountain Valley, California, built onto the existing single-story house rather than set apart from it, and paired with a 384 sq ft family room addition to the main dwelling — 1,177 sq ft of new space in total. Because the ADU shares structure with the house, the design went through a dedicated structural plan review by the city's third-party reviewer and was approved without outstanding comments. The unit was given its own electrical meter and a heat pump, while the existing sewer connection was kept. The work also reached past the property line: the water service was upsized to a 1-inch meter, a parkway tree was planted to city standard, and those public improvements were built under a separate encroachment permit with its own plan check and inspections. Demolition debris was hauled and recycled under tracked weight tickets. Completed in 2024-2025.

New construction

793 sq ft attached ADU plus a 384 sq ft family room addition — 1,177 sq ft total

Existing property

1,821 sq ft single-story house on a 7,201 sq ft R1 lot

Permit

City of Fountain Valley 2024-440, Type V-B

Code basis

2022 California Building, Green Building Standards, and Energy Codes

Services

Separate electrical meter and heat pump; water service upsized to a 1-inch meter

Public works

Parkway improvements and street tree under a separate encroachment permit