Quick answer
An ADU site plan is a scaled, top-down drawing of the whole lot that shows where the accessory dwelling unit will sit, every existing structure, and the distances from each building to the property lines.
It is the sheet a planner uses to check setbacks, lot coverage and building separation. Many plan-check corrections on ADUs trace back to a missing or wrong dimension on this page.
Quick facts
- Also called
- Plot plan
- Model code requirement
- Size and location of new and existing structures and distances from lot lines (IRC R106.2) 1
- California side and rear setback for a new ADU
- No more than 4 ft may be required (Gov. Code 66314) 3
- California completeness notice
- Within 15 business days of receiving the application (Gov. Code 66317) 4
- Part of
- The ADU plan set submitted for permit
- Who draws it
- Usually the designer or architect; a surveyor's map may be needed where lot lines are uncertain
What a site plan means, in plain English
A site plan is a map of your lot, seen from above. It is drawn to scale. It shows your house, the new ADU, and how far each one is from the edges of your land.
The edges of your land are the property lines (the legal boundary, which may not match your fence). The required gap between a building and a property line is a setback rule.
The site plan is usually the first sheet in your ADU plan set. It is also the first sheet the planner reads.
Why the site plan matters to you
It decides whether your ADU fits. If the numbers on the site plan break a setback or coverage rule, the design has to change.
It is also a common source of delay. A missing dimension means a correction notice, a fix and a resubmittal. Each round adds weeks.
Finally, builders and utility companies use it. It shows where the trench for sewer and water runs, where the meter goes, and how a crew gets equipment into the yard.
What the building code asks for
The diagram below shows what a site plan ties together. Each part is a question the plan checker will ask.
Building codes require a site plan with every new-construction permit. The 2024 International Residential Code, Section R106.2, says the construction documents must come with a site plan.
It must show the size and location of new construction and existing structures, and their distances from lot lines. For demolition, it must also show what is removed and what stays.
California applies its own Residential Code and local submittal checklists, which usually ask for more. For an ADU, the site plan answers the planner's first questions. Does the unit fit inside the buildable area? Does it keep the required setbacks? How do people, utilities and firefighters reach it?
- Lot linesWhere the property starts and ends
- Existing structuresHouse, garage and sheds, with sizes
- New ADUIts footprint and location
- DistancesFrom each structure to each lot line
- AccessHow people and firefighters reach the unit
- UtilitiesWater, sewer, power and gas routes
IRC R106.2 sets the minimum; local checklists usually ask for more. Source: [1]
Sources: [1]
What an ADU site plan should show
Use your agency's checklist as the controlling list. These items appear on most of them.
- North arrow, scale, address and parcel number.
- All property lines with their lengths, and any easements (strips of land others have a right to use, such as for utilities).
- Every existing structure (house, garage, sheds) with its footprint and use, marked to stay or be removed.
- The proposed ADU footprint, with dimensions to each property line and to the main house.
- Lot area, existing and proposed building coverage, and floor area if the city regulates it.
- Driveways, any required parking, and the path from the street to the ADU entrance.
- Utility routes: water, sewer or septic, electric and gas, with meter locations; see sewer lateral.
- Trees, slopes, drainage and any flood or fire zone noted by the agency.
Site plan, survey and other lot drawings compared
| Document | Who makes it | What it proves |
|---|---|---|
| Site plan (plot plan) | Designer, architect or sometimes the owner | Where the ADU goes and the distances that matter for zoning |
| Boundary survey | A licensed land surveyor | Where the legal property lines actually are |
| Topographic survey | A licensed land surveyor | Ground heights and slopes, for drainage and foundations |
| Utility plan | Designer or engineer | Routes and sizes of pipes and lines |
| Floor plan | Designer or architect | Rooms inside the ADU, not the lot |
California rules the site plan has to prove
Under Government Code 66314 (as amended by AB 1170, effective 1 January 2026), a local agency may require no more than four feet from the side and rear lot lines for a new ADU.
It may require no setback for an existing structure converted to an ADU, or for a new structure built in the same place and to the same size as an existing one.
Government Code 66321 (as amended by SB 543, effective 1 January 2026) bars local standards, such as lot coverage or floor area ratio, that would not allow at least an 800-square-foot ADU with four-foot side and rear setbacks. The site plan is where you show the unit meets those conditions.
The site plan also shows the ADU sits on the same lot as a primary home, proposed or existing. That is part of the ADU definition in Government Code 66313 2.
Front setbacks, fire separation and utility rules are set locally and in the building code. Check the ADU regulations hub and your city's checklist.
Rules in other states
Every state requires some form of site plan for a new home. The setback numbers it must prove differ by state and city. Do not use California's four-foot rule elsewhere. See ADU laws by state.
Example: reading the dimensions on a site plan
A hypothetical lot, 50 ft wide and 120 ft deep, with a detached ADU in the rear corner, in a California city that applies the state maximum setbacks.
| Dimension on the plan | Value drawn | What the checker compares it to |
|---|---|---|
| Lot area | 50 ft × 120 ft = 6,000 sq ft | The base for coverage math |
| ADU to rear lot line | 4 ft | No more than 4 ft may be required for a new ADU 3 |
| ADU to side lot line | 4 ft | Same 4 ft cap 3 |
| ADU to main house | Drawn wall to wall | Local and building-code separation rules |
| ADU footprint | 20 ft × 30 ft = 600 sq ft | Local size and coverage limits, subject to the 800 sq ft floor 5 |
| ADU share of the lot | 600 ÷ 6,000 = 10% | Added to the house and garage for total coverage; see lot coverage |
Every number is measured to the property line, not the fence. If the fence is off the line, the drawn setback is wrong. When the line is uncertain, a boundary survey settles it before you design.
How a site plan gets made and reviewed
- Find your parcel map and any past survey in county records.
- Measure existing buildings, or order a survey if lines are unclear.
- Test the ADU footprint with the size envelope calculator.
- Draw the site plan to scale with every item on the city's checklist.
- Submit it with the full plan set. In California, the city must tell you within 15 business days if anything is missing, and list how to fix it (Gov. Code 66317) 4.
- Fix any corrections and resubmit.
Where you will see the site plan
- Permit set: usually sheet A-1 or similar, the first drawing.
- Correction letter: items like "dimension eave to property line".
- Builder's bid: trench lengths and access routes come from it.
- Utility application: the meter and service location.
What drives the cost of a site plan
HyreADU does not publish a site plan price. We have no dated, sourced fee dataset.
The drivers are lot complexity and certainty. A flat, rectangular lot with a recent survey is quick to draw. A sloped, odd-shaped lot with no survey may need a surveyor first. Site plan work is a soft cost; include it when you use the cost calculator.
Common site-plan mistakes
- Dimensions taken from a fence or curb instead of the legal property line.
- Eaves, stairs or decks drawn but not measured to the line.
- Existing sheds or patio covers left off.
- Utility routes missing, so the reviewer cannot check meter or sewer connections; see utility connection requirements.
- Coverage math that does not add up across sheets.
- No scale, or a scale that does not match the printed size.
Real situations homeowners run into
- The fence is two feet inside the line. The owner measured 4 ft from the fence, so the ADU actually sits 6 ft from the line. That is legal, but it wastes yard. A survey would have shown the extra room.
- The fence is outside the line. Now the drawn 4 ft is really 2 ft or less. The city or a neighbor can catch it later, when it is far harder to fix.
- The forgotten shed. An old shed was left off the plan. It counts toward coverage and may block the path for utilities or firefighters.
- The converted garage. An existing garage sits 1 ft from the side line. Under Gov. Code 66314, a city may require no setback for an existing structure converted to an ADU, so the site plan should label it as existing 3.
Drawing it yourself: benefits and limits
What it does well
- Many cities accept an owner-drawn site plan if it is to scale and complete.
- You know the lot better than anyone.
Where it falls short
- Errors in property lines are costly to fix after design.
- Missing items lead to correction rounds.
- Some cities require a licensed professional for certain sheets.
What to ask your designer
- Will you measure from a survey or from records?
- Does the site plan include utility routes and meter locations?
- Who answers site-plan corrections, and is that in the fee?
- Is the coverage math shown on the sheet?
Where the site plan fits
- Zoning district → setbacks and coverage → site plan → full plan set → plan check → permit
Key takeaways
- The site plan is a scaled map of the whole lot with every distance that matters.
- Measure to the legal property line, not the fence.
- In California, a city may require no more than 4 ft side and rear setbacks for a new ADU.
- A complete site plan is the fastest way to avoid correction rounds.
Tools for the site plan stage
- Feasibility checkerScreen the lot before paying for drawings
- ADU planning hubThe steps before design
- ADU zoning statisticsHow zoning limits play out in data
Questions about adu site plan
What is a site plan for an ADU?
It is a scaled drawing of the whole lot showing the proposed ADU, existing buildings, property lines and the distances between them. The city uses it to check setbacks, coverage and access.
Can I draw my own ADU site plan?
Many cities accept an owner-drawn site plan if it is to scale and complete, but check your agency's checklist. Where lot lines are uncertain, a licensed surveyor's boundary survey avoids errors.
What setbacks apply to an ADU in California?
For a new ADU, a local agency may require no more than four feet from the side and rear lot lines (Gov. Code 66314). A converted existing structure needs no new setback.
Is a site plan the same as a plot plan?
Yes. The building code calls it a site plan or plot plan. Both mean the scaled drawing of the lot and its structures.
Do I need a survey for an ADU site plan?
Not always. If your property lines are clear and recorded, a site plan from records may be accepted. If a fence or neighbor dispute makes the line unclear, a boundary survey is the safer choice.
What scale should an ADU site plan be?
Your city's checklist sets it. The key is that the scale is stated on the sheet and matches the printed size, so the planner can measure from it.
What happens if my site plan is wrong?
The city sends a correction list. In California it must tell you within 15 business days if the application is incomplete and how to fix it. If the error is found after building, the fix can be far more costly.
Does the site plan need to show utilities?
Most city checklists ask for water, sewer, electric and gas routes and meter locations. Without them, the reviewer cannot check the connections, which is a common reason for corrections.
Sources
- International Code Council, 2024 International Residential Code, Chapter 1, Section R106.2 Site plan or plot plan, retrieved .
- California Legislature, Government Code 66313 (ADU definitions, as amended by SB 543, effective 1 Jan 2026), retrieved .
- California Legislature, Government Code 66314 (ADU standards, as amended by AB 1170, effective 1 Jan 2026), retrieved .
- California Legislature, Government Code 66317 (completeness notice and 60-day decision, as amended by SB 543, effective 1 Jan 2026), retrieved .
- California Legislature, Government Code 66321 (limits on local standards, as amended by SB 543, effective 1 Jan 2026), retrieved .
Expert review
Written by the HyreADU Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Setback, size, definition and review-deadline rules read on the current Chapter 13 text at leginfo.legislature.ca.gov; model code read on codes.iccsafe.org; 7 October 2026. The worked example uses hypothetical lot dimensions.
Suggest a correction. We fix errors and say what changed.