Screen your property against the statewide ADU and JADU standards California applies to every city: size limits, setbacks, height and whether a JADU can go in alongside. These are state minimums, not a promise of approval.
Every result is a planning estimate, not a quote or an engineering determination. Real numbers depend on site conditions, existing structure, engineering requirements, and your jurisdiction’s current fee schedule. For structural and engineering work we coordinate with a licensed engineer — we do not perform or stamp engineering ourselves. Get a project-specific estimate before committing to a budget.
California ADU law works as a floor, not a ceiling. Regardless of what a local ordinance says, a jurisdiction generally cannot block an ADU of at least 800 square feet at 16 feet in height with 4-foot side and rear setbacks. That single sentence is why so many lots that look too small on paper still pencil out. Lot coverage caps, floor area ratios, minimum lot sizes and open-space requirements cannot be used to shrink an ADU below that floor.
Above the floor, the usual state framework is: detached ADUs commonly permitted up to 1,200 square feet; attached ADUs generally limited to 50 percent of the primary dwelling floor area, subject to that same 800 square foot protection; and JADUs capped at 500 square feet, located within the existing or proposed walls of a single-family dwelling, with an interior connection to the main house and an efficiency kitchen. A garage conversion ADU is governed by the existing garage footprint, and converting that garage does not trigger a requirement to replace the lost parking.
What your city still controls is everything around the box: front setback, design and materials review, height above the state floor, tree removal, driveway and fire-access width, grading and drainage, sewer lateral capacity and impact fees. Two identical lots in Sunnyvale and Los Gatos can produce different buildable results for reasons that have nothing to do with ADU law.
Once you have a size that works, the permit submittal is a drawing problem. A typical ADU set includes a site plan with setbacks and separation distances, floor plans, exterior elevations, building sections, assembly and egress details, a door and window schedule, and electrical and plumbing layouts, alongside a registered Title 24 energy report. Our architectural drafting and design service produces that package, and the Title 24 ADU CF1R page covers how ADUs get modeled for energy compliance, which is not the same as modeling an addition.
Where a detached ADU needs a foundation design, or a garage conversion removes a shear wall when the garage door is infilled, structural sheets and calculations are prepared and stamped by an independently licensed engineer we coordinate with. We assemble the coordinated set; the engineer makes and stamps the engineering determinations. Nobody can promise you a plan check outcome, but a complete, internally consistent set is the single biggest thing that keeps correction cycles short.
On a single-family property, state law generally allows one ADU and one JADU together. The JADU is capped at 500 square feet, has to sit within the existing or proposed walls of the house, needs an interior connection to the main dwelling and an efficiency kitchen, and usually carries an owner-occupancy requirement. Duplex and multifamily parcels follow different rules and JADUs are generally not available on them.
Usually not. State law generally prevents a local lot coverage, floor area ratio or open space standard from reducing an ADU below 800 square feet at 16 feet tall with 4-foot side and rear setbacks. That protection is the reason tight lots still work. It does not override fire access, easements or flood requirements, so those still need checking.
Under state ADU law, converting a garage to an ADU generally does not require replacement parking. That exemption is specific to ADUs. Converting the same garage into a bedroom, office or family room that is not an ADU is a different question and your local zoning may still expect the off-street space.
No. It compares your inputs to statewide minimum standards and nothing more. It does not see your zoning district, easements, fire access, utilities or tree constraints, and it is not a zoning determination. Confirm at your planning counter before designing to any number here.
No. We are a drafting, design, Title 24 and permit-documentation firm. We produce the drawings and compliance documents you submit, and we coordinate with an independently licensed engineer when structural design or a stamp is required. Construction is handled by your contractor.
Tell us what you're building and we'll get back to you with next steps — usually within one business day.
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Yuna Drafting