California has become a hotspot for homeowners seeking innovative ways to increase property value, maximize living space, and accommodate growing families. One of the most popular trends driving this movement is the construction of Accessory Dwelling Units (ADUs)—compact, fully functional living spaces that offer flexibility and long-term value. Whether you’re envisioning a sleek guest house, a private home office, or a rental opportunity in your backyard, choosing the right builder is critical. This guide explores the best custom ADU builders in California, offering insights into ADU construction in Corona, CA, modern accessory dwelling unit plans, and the growing popularity of prefab accessory dwelling units.