The property determines the starting difficulty

A new detached ADU on a relatively open, documented site is a different assignment from a garage conversion, hillside project, addition to an older building, or site with uncertain records and tight clearances. Existing conditions create documentation and coordination work before the proposed rooms are resolved.

The amount and quality of available information also matters. A current survey, reliable as-built drawings, clear photographs, and confirmed utility information reduce assumptions. Missing or conflicting records can require additional field work, research, or consultant input.

Project type changes the drawing and analysis

Detached construction, attached additions, conversions, and junior ADUs involve different relationships to foundations, structure, fire separation, energy documentation, utilities, and existing occupancy. A customized design also requires a different level of exploration from a previously developed plan adapted within known limits.

The proposal should name the project type and intended program. If the owner has not chosen a direction, early design or feasibility work may need to precede a fixed permit-plan scope.

  • New detached structure
  • Garage or accessory-building conversion
  • Addition or attached ADU
  • Interior conversion or junior ADU
  • Custom design versus bounded adaptation

Consultants are separate scopes that still require coordination

Structural, civil, energy, survey, geotechnical, septic, fire-sprinkler, solar, utility, or other specialist work may be required depending on the property and jurisdiction. Their fees are commonly separate from the architectural or residential design fee unless the proposal says otherwise.

Even when consultant invoices are paid directly by the owner, someone must define the needed scope, exchange backgrounds, incorporate their information, resolve conflicts, and assemble coordinated documents. A lower plan fee can represent less coordination rather than the same service for less money.

Revision, submission, and correction support are real work

A proposal should state the included owner design rounds and distinguish them from agency corrections. It should also explain who prepares the application, submits the package, tracks status, responds to agency questions, coordinates consultant revisions, and handles resubmittal.

Those responsibilities can remain with the owner, be shared, or be carried by the design team within defined limits. More support generally costs more because it transfers time, communication, and process responsibility—not because the drawings have become physically larger.

  • Number and timing of owner design revisions
  • Included drawing and consultant coordination
  • Submission and application responsibilities
  • Status updates and agency communication
  • Plan-check response rounds and scope boundaries
  • Treatment of owner changes after approval

Professional fees are not the whole project budget

Agency plan-review, permit, school, utility, impact, and other fees may apply, and separate consultant, survey, investigation, testing, or construction costs can be significant. The responsible way to discuss a permit-plan proposal is to state which fees are included, which are allowances, and which are paid directly by the owner.

California law limits or regulates some ADU fees in certain circumstances, while local agencies maintain their own current schedules and procedures. A generic internet estimate is not a substitute for checking the current jurisdiction and project facts.

Compare proposals by responsibility and exclusions

When two fees differ, place the proposals side by side and compare the promised deliverables. Look for drawing-sheet definitions, design rounds, consultant tasks, submission work, correction support, field verification, reimbursable expenses, schedule assumptions, and conditions that trigger additional services.

The best proposal is not automatically the least expensive or the most comprehensive. It is the one that matches how much responsibility the owner wants to carry and makes the boundary around the service understandable before work begins.

  • What is the defined deliverable?
  • Which existing conditions are confirmed or assumed?
  • Who hires and manages consultants?
  • Who submits and follows up?
  • How many owner revisions and correction rounds are included?
  • Which agency, consultant, and construction costs remain separate?
Practical takeaway
Permit-plan fees reflect the property, documentation, coordination, and responsibility being accepted. Compare scopes line by line before comparing totals.

Official sources and useful references

These links are a starting point. Confirm that a page, map, handbook, or fee schedule is current when you use it.

This article provides general educational information. Property records, field conditions, consultant requirements, and jurisdiction review may change the answer for a specific project.