An Accessory Dwelling Unit (ADU) is a secondary, self-contained home located on the same lot as an existing single-family or multifamily residence. In Sacramento, ADUs are sometimes called backyard homes, in-law units, or granny flats. An ADU must have its own kitchen, bathroom, and sleeping area, and it can be attached to your main home, built above a garage, converted from existing space, or built as a new detached structure.

In Sacramento, most residentially zoned properties can support several common ADU types, subject to site conditions and current codes:

• Detached ADU – A stand-alone small home in your yard, often the most flexible option for privacy and rental potential.
• Attached ADU – An addition that shares at least one wall with your existing house.
• Garage conversion ADU – Turning an existing garage into a livable unit. You can often add a small addition to expand the footprint.
• Above-garage ADU – A new unit built above an existing or new garage.
• Interior conversion ADU – Converting part of your existing home (like a basement or large bonus room) into a separate dwelling.
• Junior ADU (JADU) – A smaller, more limited unit created within the footprint of your existing home (explained below).

Onsum can help you determine which type best fits your lot, budget, and goals during an initial consultation.

A Junior ADU (JADU) is a smaller accessory unit created entirely within the existing walls of your primary home, typically up to 500 square feet, as allowed under California state law. A JADU must have its own separate entrance and at least an efficiency kitchen, but it can share a bathroom with the main house. JADUs are a great option when you want a rentable space, a separate suite for family, or flexibility on a tighter budget without building a new structure in your yard.

Yes. Any new ADU in the City of Sacramento requires building permits. There are no legal shortcuts. Attempting to build without permits can result in stop-work orders, fines, forced demolition, and problems when you try to sell or refinance your property.

Breakdown of the Permit Timeline

• Legal Mandate (State Law): Under California law, cities must process ADU permit applications within 60 days of receiving a complete application.
• First Plan Check: Usually takes about 2–4 weeks for the city to review your submitted plans.
• Correction Cycles: If the city requires changes to your plans, each correction cycle adds time — typically 1–2 weeks per round.

Factors That Impact the Timeline

• Custom vs. Pre-Approved Plans: Using pre-approved or standard plans can significantly speed up approval.
• Project Type: Garage conversions or interior conversions often move faster than new detached structures.
• Utility Coordination: Separate clearances from SMUD, Sacramento Regional, or other utilities can add weeks.

Timelines vary based on project complexity, plan completeness, and current city workload. A straightforward garage conversion with clean plans might be approved in 4–8 weeks. A custom detached ADU could take 3–6 months from application to permit issuance. Onsum’s experience with Sacramento’s permitting process helps minimize delays.

California state law currently requires cities to allow ADUs with a minimum 4-foot rear and side setback for detached ADUs up to 800 sq ft. Larger ADUs or attached ADUs may be subject to the standard zoning setbacks for the property. Front setback requirements still apply. Onsum reviews your specific lot to identify the most buildable area.

For most new ADUs permitted in California after 2020, there is currently no owner-occupancy requirement for the primary residence. This means you can own a property, rent out both the main house and the ADU, and not live on-site. However, rules for Junior ADUs (JADUs) may differ. Onsum stays current on any changes to these requirements.

Most residentially zoned lots with an existing primary dwelling are eligible for at least one ADU. However, not every lot can physically or legally support one. Key factors include:

• Lot size and shape
• Location of existing house, garage, and trees
• Setbacks, easements, and access requirements
• Flood zones, slopes, or other environmental constraints
• Historic or design overlay districts, if applicable

During Onsum’s initial feasibility review, we assess your specific property to determine what’s possible and what type of ADU makes the most sense.

State law requires cities to allow ADUs up to at least 850 sq ft for studios/one-bedrooms and up to 1,000 sq ft for two or more bedrooms, regardless of lot size. Sacramento may allow larger ADUs depending on your zone and lot size — sometimes up to 50% of the primary home’s square footage.

Because local interpretations and updates happen regularly, Onsum always verifies the current maximums for your specific parcel before designing.

In many residential zones, yes. Two-story ADUs are allowed in Sacramento, subject to height limits (typically 16–18 feet for detached ADUs), setbacks, and design review requirements in some neighborhoods. An above-garage ADU is a common two-story configuration. Onsum’s design team handles two-story ADU projects regularly.

Yes. An ADU must have a separate, lockable entrance that does not require passing through the primary residence to access. A JADU may share a doorway with the main home as long as it has its own exterior entrance. This is a hard requirement for the unit to be legally classified as an ADU.

Yes, there are strict limits on how many ADUs you can add to a property, and they depend on your property type.

1. Single-Family Residential Properties

Under both Sacramento local rules and California state law, a single-family lot may have:

• Option A: Up to 2 standard ADUs (though this depends on lot size and configuration).
• Option B: 1 standard ADU + 1 Junior ADU (JADU) — this is one of the most common combinations.

2. Multi-Family Properties (Duplexes, Triplexes, etc.)

If the property contains multiple existing units:

• Conversion ADUs: You are permitted to convert up to 25% of existing units into ADUs (e.g., converting storage rooms, garages, or other non-habitable spaces).
• Detached ADUs: You can build up to 2 new detached ADUs on the lot, separate from conversions.

Practical Physical Limits

Even if zoning technically allows multiple ADUs, your lot must physically accommodate them:

• Lot Coverage & Setbacks: Maintaining required open space and setbacks often limits how many structures fit.
• Separation Requirements: Detached structures must maintain minimum distances from each other and from property lines.

Total ADU costs depend on size, design, type, site conditions, and finishes. General ranges in Sacramento: Garage or interior conversions: $80,000–$150,000+. New detached ADUs: $150,000–$350,000+. High-end custom ADUs: $350,000+.

During your initial consultation, Onsum provides a realistic cost range based on your specific project scope, not a generic estimate.

Yes. Many Sacramento homeowners finance ADUs using:

• Home equity lines of credit (HELOCs)
• Cash-out refinancing
• Construction or renovation loans
• Personal loans for smaller JADU or conversion projects
• Specialized ADU loan products offered by some California lenders

Onsum can connect you with lenders familiar with ADU financing in Sacramento.

California law significantly limits impact fees for ADUs under 750 sq ft and prohibits them entirely for JADUs. In addition, Sacramento has periodically offered incentive programs for affordable ADUs or low-income homeowners.

These programs change over time. Onsum stays current on available incentives and can advise you during your consultation.