ADU Construction in Modesto

An accessory dwelling unit (ADU) adds a complete, permitted living space on the lot you already own: room for aging parents or grown kids, a home office, or rental income that helps cover the mortgage. TDI^® builds ADUs in Modesto and across Stanislaus County, and manages each project from the first site review to the final inspection under one contract.

ADUs we build in Modesto

• Detached ADUs, a standalone backyard cottage with its own foundation, kitchen, bathroom and entrance
• Attached ADUs, a new unit built onto the existing home with its own entrance
• Garage conversions, turning an attached or detached garage into a full living unit
• Junior ADUs, up to 500 square feet carved out of existing space inside the home, with an efficiency kitchen and a separate entrance
• Above-garage units, where the lot and local rules allow it

Building an ADU in Modesto

Modesto is the Stanislaus County seat, where a large share of homes were built from the late 1940s through the 1970s, alongside newer neighborhoods on the city’s edges.

Most Modesto lots can fit at least one type of ADU. A detached unit works where the backyard has room, while a garage conversion reuses an existing structure and is often the fastest path to a permitted unit.

Older homes often need an electrical service upgrade to carry a second unit, and sewer and water lines may need to be replaced or upsized for the new connection. We check the panel, the sewer lateral and the water service early so those costs are in the estimate, not a surprise during construction.

Northern San Joaquin Valley summers regularly pass 100 degrees, and winters bring tule fog and rain. We design ADUs to California Title 24 energy standards, with insulation, window placement and a properly sized heating and cooling system so the unit stays comfortable year round.

How an ADU project works with TDI^®

1. Site and zoning review. We look at your lot, setbacks, utilities and access before anything is drawn, so the design fits what can be permitted.
2. Design and drawings. We coordinate floor plans and construction drawings sized to your goals and budget.
3. Permits and plan check. We submit the application to the City of Modesto building division, answer plan check comments and track the permit through approval.
4. Construction. Foundation, framing, roofing, plumbing, electrical and HVAC, insulation to Title 24, then drywall, cabinets, fixtures, flooring and finishes.
5. Final inspection and walkthrough. We close the permit and walk the finished unit with you, so you have a legal, insurable, rentable space.

Licensed and accountable

• CSLB licensed general contractor, License #1041773, Class B General Building
• Native American owned (Cherokee) and a certified Minority Business Enterprise
• Building in Northern California since 1983

Thinking about an ADU in Modesto? Call us for a site review and a free written estimate.