ADU Permit Cost

Nationally, ADU permit fees typically range from $3,000 to $12,000, covering plan checks, building permits, impact fees, and utility connections.

In California, under AB 68, local agencies cannot charge impact fees for ADUs under 750 square feet.

For California ADUs 750 square feet or larger, impact fees must be charged proportionally to the square footage of the primary dwelling.

California school districts can levy impact fees on ADUs larger than 500 square feet, per Education Code Section 17620.

A garage conversion permit in Los Angeles costs approximately $1,500, as it does not add new square footage or trigger impact fees.

The rest of it, in plain terms

• A new 1,200 sq ft detached ADU permit in Los Angeles costs approximately $7,500, including school district fees and energy surcharges.
• Plan check fees typically range from $500 to $2,500 and pay for staff time to review drawings, not the permit itself.
• The ADU permitting process generally takes 6 to 16 weeks, involving pre-application checks, plan reviews, and correction rounds.
• Washington state caps ADU impact fees at 50% of what a primary home pays.
• Utility connection or capacity fees are often overlooked by homeowners and can add $500 to $3,000 to the total permit cost.

Figures below are researched market numbers for budgeting and comparison. They are not quotes. Final pricing depends on your site, your jurisdiction, finish selections, foundation and utility distance.

• National Average Permit Fees: $3,000 to $12,000 total (Source: ADU Wizard)
• Plan Check Fees: $500 to $2,500 (Source: ADU Wizard)
• Building Permit Fees: $1,500 to $4,000 (Source: ADU Wizard)
• Impact / Development Fees: $0 to $5,000+ (Waived in CA for ADUs under 750 sq ft) (Source: ADU Wizard)
• Utility Connection Fees: $500 to $3,000 (Source: ADU Wizard)
• School District Fees: $0 to $1,500 (Triggers at 500+ sq ft in CA) (Source: ADU Wizard)
• Los Angeles Garage Conversion Permit: ~$1,496 (Based on $75,000 project valuation) (Source: Cali-ADU)
• Los Angeles 1,200 sq ft Detached ADU Permit: ~$7,479 (Based on $150,000 project valuation) (Source: Cali-ADU)

ADU rules are set locally and change often. These are the provisions that most commonly control the outcome. Verify against your own jurisdiction before you design anything.

• California AB 68 / AB 881 / SB 13: Prohibits local agencies from imposing impact fees on ADUs under 750 square feet. For ADUs 750 sq ft or larger, impact fees must be charged proportionately in relation to the square footage of the primary dwelling unit.
• California Education Code Section 17620: Authorizes school districts to levy impact fees for ADUs greater than 500 square feet. ADUs less than 500 sq ft are exempt from school impact fees.
• California Government Code Section 66314: Regulates ADU application approvals and denials based on building code violations.
• 2024 International Residential Code (IRC) Appendix BC (BC101.2): Specifies that an ADU shall have a maximum of two bedrooms, and detached ADUs must comply with location requirements in Section R302.
• Washington State ADU Guidance: Requires cities to allow two ADUs per lot and caps impact fees at 50% of what the primary home pays.
• Oregon State Law: Requires cities with populations over 2,500 to allow at least one ADU by right, with no parking or owner-occupancy requirements.

Permit cost is several separate charges that get collapsed into one word, and they behave differently. The building permit fee itself is usually calculated from construction valuation and is rarely the largest component. Plan check is a separate fee for reviewing your drawings. Impact fees are charges for the unit's incremental demand on infrastructure such as water, sewer, parks, transportation and schools, and they are frequently the largest single line.

The most useful thing to know is that several jurisdictions and some state statutes waive impact fees entirely for ADUs below a defined square footage. Where that applies, the marginal cost of crossing the threshold is not the construction cost of the extra square feet but the entire impact fee package that the waiver would have covered. That can make a slightly smaller unit substantially cheaper.

Also budget for the charges that are not permits but arrive at the same time: utility connection or capacity charges paid to the water and sewer provider, electrical service upgrade if your panel cannot carry the additional load, and any required third-party reports. Ask your building department for a written fee estimate for your specific project. Most will provide one, and it is far more reliable than any general figure, including the ones on this page.

The separate charges inside 'permit cost'

Most pages on this subject put the cost behind a contact form. The reasoning is understandable and the result is that you cannot budget, cannot compare, and cannot tell whether a bid is reasonable until you have already given up your phone number to three companies.

We publish the figures instead. They are researched market ranges rather than quotes, and site conditions will move them more than any other factor, but a range you can plan against beats a call-back you have to wait for. The constraints that decide feasibility — setbacks, height, utility distance, site access — are stated up front for the same reason. If your project is not viable, that is worth knowing on the first visit rather than the third phone call.

Factory production windows move with queue depth, material lead times and seasonal demand. We quote the current window rather than a fixed promise, because anyone promising a specific delivery date months out without seeing the factory schedule is guessing. Permitting is usually the longer pole: in ministerial states the review clock is defined by statute, while in discretionary jurisdictions it can run considerably longer.

The sequence that controls your schedule is site plan, permit submittal, plan check and corrections, permit issuance, factory slot, delivery and set, then utility connection and final inspection. Factory build time overlaps permitting only if you commit to the slot before permits are issued, which carries its own risk.