Custom Home: ADU Design and Construction in the Bay Area
Custom Home is a licensed general contractor that has been designing and building accessory dwelling units across the Bay Area since 2005. With CSLB license #986048 and over 160 completed projects, they work across the South Bay, Peninsula, and surrounding areas. Their approach separates the design phase from construction, meaning clients see every detail in 3D and review costs line by line before any work begins.
They handle a range of ADU types, including detached ADUs, attached ADUs, junior ADUs, and garage conversions. Each project goes through a structured two-phase process intended to eliminate surprises during construction.
Types of ADUs Custom Home Builds
Detached ADUs (DADUs) are standalone structures built on the same lot as the primary residence. Under California law, these can be up to 1,200 square feet and typically include a full kitchen, bathroom, and independent entrance. Common uses include backyard bungalows, guest houses, and rental units.
Attached ADUs (AADUs) connect directly to the existing home, usually along the side or rear. Because they share a wall with the main structure, they can make use of existing utility connections and infrastructure.
Junior ADUs (JADUs) are units of no more than 500 square feet created entirely within an existing single-family home. This typically involves converting a spare bedroom or a section of the house into an independent living area. JADUs are generally the most affordable ADU option since they rely on existing structure rather than new construction.
Garage conversions transform an existing attached or detached garage into a livable space. This is considered a cost-effective path to adding an ADU without building from the ground up. Garage conversions tend to have shorter timelines compared to detached units.
Full permit management is included in their service. Custom Home handles the complete permitting process from initial plans through final inspection and certificate of occupancy. They are familiar with the specific requirements of cities including San Jose, Palo Alto, Los Gatos, and Cupertino.
How Custom Home Approaches ADU Projects
Their design-first process means all decisions — materials, finishes, costs — are locked in during the design phase. Every material is specified and priced line by line before signing. There are no allowances or lump-sum estimates. When clients follow the full two-phase process, the goal is zero change orders during construction.
Project communication is structured around weekly updates with photos and milestone reports. A dedicated project manager serves as the single point of contact throughout the project. All subcontractors used are licensed and insured, and their work is directly supervised on-site.
Custom Home uses a progress-based payment structure tied to construction milestones, in compliance with California law, which limits initial deposits to $1,000 or 10% of the contract price, whichever is less.
In terms of cost, ADU projects in the Bay Area typically range from around $120,000 for a garage conversion to $500,000 or more for a larger detached unit. Key factors affecting cost include:
- ADU type (detached, attached, garage conversion, JADU)
- Square footage
- Kitchen and bathroom fixtures
- Utility connection requirements
- City-specific permit requirements
All pricing is approximate and determined on a project-by-project basis during the design phase.
Typical project timelines run from 6 to 12 months from design to move-in. Garage conversions are generally the fastest at 4 to 6 months, while detached units typically take 8 to 12 months including permitting.
Homeowners can verify Custom Home's contractor license directly on the California Contractors State License Board website at cslb.ca.gov by searching for license number 986048.
