Quick answer
There is no supported citywide ADU price range in the official sources provided for this guide. Obtain property-specific proposals and keep contractor pricing separate from Planning fees, development impact fees, permit charges and inspection fees. Confirm current requirements with San Francisco Planning and the Department of Building Inspection.
How much does an ADU cost in San Francisco?
The available official sources don't provide a typical total construction cost or cost-per-square-foot benchmark. That means a reliable estimate must come from written proposals prepared for the property and proposed ADU scope rather than an unsupported citywide average.
Ask every bidder to price the same plans or written assumptions. Proposals should identify included work, exclusions, allowances and services priced separately. This creates a useful comparison even when the bids have different totals.
What an ADU budget should include
| Budget category | What to request | Where to verify it |
|---|---|---|
| Construction | Labor, materials, site work, finishes and the exact work included in the proposal | Written contractor proposal |
| Design and engineering | Included professional services, separately priced services and coordination responsibilities | Designer, engineer and contractor proposals |
| Permit coordination | Document preparation, submission, responses to review comments and inspection scheduling | Written scope from the responsible professional |
| Permit and inspection charges | Separate entries rather than one combined allowance | Department of Building Inspection |
| Planning fees | A project-specific estimate using the Planning fee resources | San Francisco Planning |
| Development impact fees | An estimate for the proposed development project | San Francisco Planning |
| Allowances | The products or selections covered, the allowance amount and how differences will be handled | Written contractor proposal |
| Exclusions and undefined work | Conditions the bidder did not price and the process for pricing later work | Written contractor proposal |
Heads up: Do not combine an estimated contractor price and estimated government charges without showing them as separate entries. Confirm the charges associated with the proposed project through San Francisco Planning and the Department of Building Inspection.
A practical pre-bid workflow
- Research the property record. The Department of Building Inspection provides systems for tracking permit status and history and maintains building records that include plans, permit applications and job cards.
- Define the proposal. Write down the intended location and scope. San Francisco Planning promotes an ADU Permit Review RoundTable focused on creating housing in a basement, garage or backyard.
- Prepare consistent project information. Give each prospective contractor the same plans, written scope or project assumptions.
- Estimate government charges separately. Use San Francisco Planning's fee resources and Development Impact Fee Calculator, and review DBI's information about permit and inspection fees.
- Request itemized proposals. Require separate entries for construction, professional services, permit coordination, allowances and exclusions.
- Normalize the bids. Compare each proposal against the same worksheet and identify missing work before comparing totals.
- Verify the contractor. Check the contractor's license through the California Contractors State License Board before signing.
Planning fees and development impact fees
San Francisco Planning provides an interactive fee schedule and calculator for exploring Planning fees and estimating project costs. It also provides a Development Impact Fee Calculator for estimating impact fees for a development project.
San Francisco charges impact fees on new development projects to provide public services to the new building. Use the Planning resources to research these charges and ask Planning to identify the fees associated with the proposed project.
Building permits, records and inspections
The San Francisco Department of Building Inspection approves construction plans and issues construction permits in the city. It checks proposed construction against safety requirements and conducts inspections for compliance with code requirements and the permitted scope.
DBI publishes information about fees for permits, inspections and penalties. Ask the contractor or design professional whether permit coordination is included in the proposal, then list government charges separately in the budget.
DBI also provides systems for tracking building permit status and history. Its building records include plans, permit applications and job cards, which can be reviewed while researching the property and its permit history.
Basement, garage and backyard ADU concepts
San Francisco Planning promotes an ADU Permit Review RoundTable focused on creating housing in a basement, garage or backyard. Review the current information from San Francisco Planning before finalizing the concept used for contractor bids.
For bid comparison, provide every contractor with the same concept documents and ask each bidder to list assumptions, exclusions and allowances. This is editorial budgeting guidance rather than a city requirement.
Code change for applications filed in 2026
According to DBI, permit applications filed in San Francisco on or after January 1, 2026 must use the 2025 California Codes and 2025 San Francisco Code Amendments, with no grace period. The California Energy Commission states that the 2025 Building Energy Efficiency Standards also take effect on January 1, 2026.
Heads up: Confirm current filing and code requirements directly with the Department of Building Inspection before relying on a design, proposal or budget.
How to compare ADU contractor proposals
| Comparison item | Bidder 1 | Bidder 2 | Bidder 3 |
|---|---|---|---|
| License verified through CSLB | |||
| Construction scope itemized | |||
| Design and engineering identified | |||
| Permit coordination identified | |||
| Government charges separated | |||
| Allowances listed | |||
| Exclusions listed | |||
| Payment schedule tied to completed work or delivered materials |
The California Contractors State License Board licenses and regulates California's construction industry and provides tools for checking contractor licenses. Verify the displayed license information rather than relying only on a license number shown in a proposal.
CSLB says its home-improvement payment rules apply to residential ADU construction. Under its guidance, a down payment must not exceed $1,000 or 10 percent of the total contract price, whichever is less. Additional payments must be clearly listed in the contract and based on the actual value of completed work or materials delivered to the home.
Note: This is a summary of CSLB information, not legal advice. Review CSLB's current guidance and the project-specific contract before signing or making a payment.
For contractor research and matching, visit Find a California ADU Contractor.
San Francisco ADU cost FAQs
Frequently asked questions
Is there a typical San Francisco ADU price per square foot?
The official sources provided for this guide do not publish a typical total construction price or cost-per-square-foot figure. Obtain written estimates based on the property and a consistent project scope.
What should an ADU estimate separate?
Ask for separate entries covering construction, design and engineering, permit coordination, allowances, exclusions, DBI permit and inspection charges, Planning fees and estimated development impact fees.
Where can I estimate Planning and development impact fees?
San Francisco Planning provides an interactive fee schedule and calculator for exploring Planning fees and estimating project costs. It also provides a Development Impact Fee Calculator.
Which agency approves plans and conducts inspections?
The San Francisco Department of Building Inspection approves construction plans, issues permits, checks proposed construction against safety requirements and conducts inspections for compliance with code requirements and the permitted scope.
Can I research previous permits for the property?
DBI provides systems for tracking building permit status and history. It also maintains building records that include plans, permit applications and job cards.
Can I discuss a basement, garage or backyard ADU with the city?
San Francisco Planning promotes an ADU Permit Review RoundTable focused on creating housing in a basement, garage or backyard. Consult San Francisco Planning for its current information.
How do I verify a California ADU contractor?
Use the license-checking tools provided by the California Contractors State License Board and review the license information displayed for the contractor.
What does CSLB say about payments for residential ADU work?
CSLB says the down payment must not exceed $1,000 or 10 percent of the total contract price, whichever is less. It also says additional payments must be listed clearly in the contract and based on the actual value of completed work or materials delivered to the home.