Garage Conversion Contractors in Sunnyvale, CA
Sunnyvale allows a garage to be converted into an accessory dwelling unit (ADU), a junior ADU or added living space. A conversion ADU on a single-family lot is approved with a building permit only, has no maximum size beyond the existing space, and is exempt from incremental sewer and water connection fees. Design by M&M designs, permits and builds garage conversions in Sunnyvale, from the first feasibility check through final inspection. We bring 22+ years of experience, 1,000+ completed projects and CSLB license #1082131.
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Garage Conversion Options in Sunnyvale
Many Sunnyvale neighborhoods are made up of single-story homes with an attached garage, including mid-century Eichler tracts. That garage is often the largest underused space on the lot. Converting it can create a rental unit, a home for parents or adult children, or extra room for your own household, and Sunnyvale’s rules make it possible to add a separate backyard ADU later as well.
Garage to conversion ADU
Sunnyvale defines a conversion ADU as one created by converting part of an existing main building or accessory structure, which includes an attached or detached garage. It must be at least 150 square feet and has no set maximum beyond the existing space.
Garage to junior ADU
A junior ADU of up to 500 square feet is created inside the existing home. An owner-occupancy deed restriction is required only when the JADU shares a bathroom with the main house.
Garage to added living space
A garage can also become part of the main house, such as a bedroom suite or family room. This follows standard zoning and building rules rather than the ADU rules, so we confirm floor area and parking during feasibility.
Planning for more than one unit
A single-family lot in Sunnyvale can have up to three ADUs: one new construction ADU, one conversion ADU and one JADU. One limit matters for garages: a lot cannot have both a conversion ADU inside the main building and an attached new construction ADU.
Sunnyvale Rules That Shape a Garage Conversion
State ADU law sets the baseline, and the City of Sunnyvale applies its own standards on top. These are the rules that matter most for a garage conversion:
- No replacement parking for a garage ADU
- No owner occupancy required for an ADU
- JADUs up to 500 sq ft with a deed restriction
- 60-day decision on a complete application
- Approval: conversion ADUs and JADUs on single-family lots qualify for streamlined, building-permit-only review.
- Size: at least 150 square feet, with no maximum for a conversion. Up to 800 square feet of each ADU is excluded from floor area and lot coverage calculations.
- Parking: state law prevents the city from requiring replacement parking when a garage is converted to an ADU.
- Entrance: every ADU needs its own separate entrance.
- Fees: conversion ADUs are exempt from incremental sewer and water connection fees, and school impact fees apply only to new construction ADUs. A transportation impact fee applies to ADUs over 750 square feet.
- Rentals: short-term rentals are prohibited for ADUs approved after January 1, 2020.
- Easements: an ADU cannot sit in any part of an easement that prohibits permanent structures.
We confirm current requirements with the City of Sunnyvale before design is finalized. Read more about ADU construction in Sunnyvale.
The Sunnyvale Permit Process
- Feasibility and design. We check the garage, slab, ceiling height, electrical service and sewer line, confirm zoning and any easements, and design the conversion.
- Building permit submittal. Because a conversion ADU is streamlined, it goes straight to a building permit without a separate planning permit.
- Plan review. Building staff review the plans for code compliance. If comments come back, we revise and resubmit.
- Construction and inspections. The city inspects the work through final. Once signed off, the property is billed for utilities as a two-unit property.
State law requires the city to act on a complete ADU application within 60 days. A complete first submittal is the best way to keep that clock moving. Read more about garage conversion permits in California.
What Makes Sunnyvale Garages Easier or Harder to Convert
- Electrical service: Sunnyvale calls for a 100-amp subpanel at the ADU and 200-amp service at the main home, subject to PG&E availability, so many older homes need a service upgrade.
- Sewer line: if the property will have more than five toilets in total, the building sewer must be upgraded to a 4-inch line with cleanouts.
- Fire sprinklers: an attached ADU needs sprinklers if the main home has them.
- Eichler homes use post-and-beam framing and radiant floors, so we plan the conversion carefully to respect the original design.
- Older slabs often slope toward the door and lack a vapor barrier, so most conversions need a new level floor.
See is my garage a good candidate for conversion? for the full checklist, and what affects the cost of a garage conversion for budget planning.
How Long Does a Sunnyvale Garage Conversion Take?
Plan for three phases. Design and engineering come first. City plan review follows, and its length depends on the city and on how complete the first submission is. Construction typically takes 8 to 12 weeks once permits are issued, depending on the slab, structural and utility work. We give you a schedule for all three phases at the start, so you can plan around move-in or tenant dates.
Design by M&M handles design, engineering, permits and construction under one contract, so you work with one team from the first site visit to the final inspection. Learn more about our garage to ADU conversion services across the Bay Area.
Our Design-Build Process
Consult & Feasibility
We visit the garage, check the slab, panel, sewer and lot, and confirm what your city allows: ADU, JADU or added living space.
Design & Permits
Floor plans, 3D design previews and a detailed estimate, then structural and Title 24 drawings, submittal and plan check through permit issuance.
Build & Final Inspection
Our team builds the slab, framing, utilities, insulation and finishes, then closes out the permit with the city and walks you through the finished space.
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Frequently Asked Questions
If you don’t see your question answered here, please don’t hesitate to contact us directly – we’re always happy to help.