Methodology
Where our ADU permit fee estimates come from and how to double-check the numbers before you budget a project.
These are early-budgeting estimates, not official fees
Where the fee data comes from
Each displayed range is a GetYourPermit research estimate. We combine several inputs because most cities do not publish one all-in ADU price:
- Published fee schedules, ADU pages, permit portals, and formulas available for that city.
- Project-planning experience and industry research for charges that depend on staff review, outside agencies, utilities, or project details.
- Local construction-value assumptions used only when a fee depends on estimated project valuation.
Direct reference links remain visible so homeowners can inspect current published material. A reference supports the investigation; it does not make the displayed range a government quote.
Project scenarios
Every city is researched on the same 11-scenario grid: junior ADUs at 400 and 500 sq ft; garage conversions at 400 and 600 sq ft; attached ADUs at 600, 800, and 1,000 sq ft; and detached ADUs at 600, 800, 1,000, and 1,200 sq ft. A custom size uses the nearest scenario within the same impact-fee band.
The resolver never crosses the 750 sq ft impact-fee threshold when a scenario exists on the correct side. For example, 749 and 750 sq ft stay in the exempt band and use its nearest reference, while 751 sq ft uses an above-threshold reference.
What the estimate does and does not include
Each scenario contains low, typical, and high values across fixed categories. Component values must add exactly to the displayed totals, stay within reasonable planning bounds, and preserve zero development impact fees at 750 sq ft or less.
The underlying research covers:
- Building permit fees
- Plan check fees
- Development impact fees
- School district fees
- Utility connection charges
- Inspection fees
- Technology and records surcharges
Permit-fee amounts exclude architectural, engineering, financing, and construction cost. The report shows construction as a separate industry-average budget section, never as a permit fee or contractor quote.
Quality controls
Before a research set is imported, every city must contain all 11 scenarios and all nine categories. Automated checks reject missing cities, reversed ranges, component-total mismatches, unsupported reference URLs, implausible totals, and impact fees assigned below the statewide threshold. Warnings remain visible to our review process instead of being silently discarded.
How to verify with your city
Before you finalize a budget, call or visit the building department for your city and:
- Ask for the current fee schedule that applies to ADUs.
- Ask whether development impact fees apply at your specific square footage.
- Get the fee estimate in writing before you commit to a budget.
Permit process guides
Where available, permit process guides are summarized from official city pages to explain where to apply, what to prepare, and how the review typically proceeds. Not every city has a guide yet — where one is missing, we say so rather than guessing at a process we have not verified.
Corrections and known limits
We would rather be candid about the gaps than smooth them over:
- Some City fees depend on staff-assigned valuation, parcel conditions, or a project-specific quote.
- School, utility, county, and other agency charges remain separate from City Building Permit fees.
- When an amount requires City verification, the report links the applicable official source.
Who prepares this
This site is prepared by GetYourPermit editorial team. Read more about the project on the about page, or email hello@getyourpermit.app if you spot a number that looks wrong.