You have already decided that you want an ADU.
The next question is more important than most homeowners expect:
What exactly has to be included in the permit drawing package?
A California ADU permit is not usually one drawing. A detached backyard unit may require coordinated site, architectural, structural, energy, and utility documentation. A garage conversion may reuse an existing structure, but that does not automatically make the permit set simpler. Existing foundations, wall construction, new openings, insulation, plumbing, electrical work, HVAC, and fire separation can all affect the drawings.
California also has strong statewide ADU laws, but state authorization does not eliminate local building review. The California Department of Housing and Community Development continues to update its ADU guidance, with the current handbook updated in March 2026. Local cities and counties still administer permit submittals and can require project-specific information consistent with applicable state law and building codes.
That is why we treat California ADU plans as a coordinated permit package rather than a collection of unrelated sheets.
If you already know you are moving forward with an ADU, our ADU Permit Plan service is the relevant starting point. If you are not yet sure what can physically fit on the property, use the ADU Feasibility Checker before drafting begins.
The permit package should follow the project in a logical order. Feasibility comes first. The site plan establishes what fits. Architectural drawings define the dwelling. Structural drawings explain how it stands. MEP and utility plans make it functional. Title 24 addresses energy compliance. Everything should coordinate before the set reaches plan review.
Start With Site Feasibility Before You Start Drawing the ADU
A good California ADU permit set starts before the first floor-plan wall is drawn.
The first question is not whether the kitchen should be on the left or right side of the unit.
It is whether the proposed ADU works on that specific property.
The property needs to be reviewed for existing structures, available building area, setbacks, access, easements, utility conditions, grading or drainage issues, fire-related conditions, and other constraints that can affect the design.
This matters because an architecturally attractive 800-square-foot ADU is useless if the selected location conflicts with a utility easement or requires a foundation solution that was never considered in the budget.
California jurisdictions increasingly provide dedicated ADU checklists and tools for this reason. Tulare County, for example, tells applicants to verify the property, zoning, water or sewer capacity, and applicable fire or access requirements before preparing the final plans.
Our own California site plan guide follows the same principle: California requirements must be checked against the actual jurisdiction and parcel, not treated as one universal city checklist.
Once feasibility is understood, the site plan becomes the foundation for the rest of the drawing set.
The ADU Site Plan Establishes How the Entire Property Works
An ADU site plan is more than a box showing where the new unit will sit.
It should give the reviewer enough information to understand the relationship between the ADU, the primary residence, property boundaries, access, utilities, and other site conditions.
For a typical project, that can include:
- Property lines, dimensions, existing structures, and proposed ADU footprint
- Required setbacks and distances between structures
- Driveway, pedestrian access, parking where applicable, and easements
- Utility locations or proposed connection routes where required
- Lot information and other jurisdiction-specific site notes
California counties publish similar requirements. Tulare County states that its ADU plot plan should identify existing and proposed structures, property lines, setbacks, driveways, wells, septic systems, easements, and other significant site features.
This is why the site plan should be coordinated before architectural design becomes too advanced.
If the proposed footprint moves six feet during zoning review, the floor plan, utility route, roof geometry, structural foundation, and energy model may all need to change with it.
For property-level drawing support, our Residential Site Plans service covers the site-planning side of residential permits.
But the site plan is only the first sheet group. Once the reviewer understands where the ADU goes, the package must explain what exists now and what is being proposed.
Existing Conditions Are Especially Important for Garage Conversions
Existing-condition drawings are easy to underestimate.
For a detached new ADU, the project starts largely from a new building design.
A garage conversion begins with an existing structure, and that means the designer must document what is already there before showing what changes.
The existing plan may need to establish current wall locations, garage openings, windows, doors, ceiling or roof configuration, slab conditions, attached structures, and the relationship between the garage and the primary residence.
Why?
Because the permit reviewer needs to distinguish between:
existing construction that remains,
existing construction that is removed, and
new construction being added.
That distinction becomes critical when a garage door opening is infilled, new windows are cut into existing walls, a bathroom is introduced, or structural walls are modified.
A garage conversion may look simple because the roof and walls already exist. In practice, the permit package often requires more investigation of existing conditions than a detached new ADU.
Once those existing conditions are documented, the proposed architectural plan can be developed accurately.
The Proposed Floor Plan Defines the ADU as a Dwelling
The proposed floor plan is where the project stops being simply an accessory structure and becomes a dwelling.
It shows how the unit functions.
The drawing typically establishes room arrangements, dimensions, interior and exterior walls, doors, windows, kitchens, bathrooms, fixtures, circulation, and other building elements needed for plan review.
For a detached ADU, the floor plan is developed around a new structure.
For a garage conversion, the challenge is fitting a functional dwelling into an existing shell while coordinating new openings, plumbing, mechanical systems, structural constraints, and usable room dimensions.
The floor plan also affects almost every drawing that comes afterward.
Move the bathroom and the plumbing plan changes.
Move a window and the elevation changes.
Widen an opening and structural review may change.
Move the mechanical equipment and Title 24 documentation may need to follow.
This is why a strong permit set is coordinated rather than prepared sheet by sheet in isolation.
California jurisdictions commonly expect floor plans as part of ADU submittals. Contra Costa County, for example, identifies the site plan, floor plan, and architectural elevations among the plan-set components used in its planning application process.
After the floor plan establishes how the unit works internally, the roof and exterior drawings establish how the building works as a complete structure.
The Roof Plan, Elevations and Sections Complete the Architectural Story
A floor plan shows the ADU horizontally.
The rest of the architectural set has to explain it vertically and externally.
The roof plan shows the roof configuration, slopes, ridges, valleys, overhangs, drainage direction, and relationships to walls below where applicable.
Exterior elevations show what the ADU looks like from each required side. They communicate heights, roof geometry, window and door locations, exterior materials, grade relationships, and other visible building conditions.
Sections cut through the structure.
They help the reviewer understand relationships that cannot be seen clearly on a floor plan: foundation to wall, wall to roof, floor elevation, ceiling height, roof assembly, insulation zones, and important construction transitions.
These sheets are not decorative illustrations.
They coordinate zoning height review, structural design, energy compliance, and construction details.
A window drawn on the floor plan must appear in the correct position on the elevation. The wall assembly shown in section must agree with the energy documentation. The roof design must coordinate with structural framing.
That is where permit-set quality becomes visible.
Structural Plans Turn the Architectural Design Into a Buildable ADU
Once the architectural geometry is established, the project has to demonstrate how the structure will support itself.
For a new detached ADU, structural documentation may address the foundation, slab or raised-floor system, wall framing, beams, headers, roof framing, hold-downs, anchorage, connections, and other structural elements.
For a garage conversion, structural review often focuses on different questions.
Can the existing foundation support the proposed residential use and modifications?
What happens when the garage door opening is infilled?
Do new window or door openings affect shear-wall capacity?
Are existing rafters or trusses being modified?
Does removing an interior wall create a new beam requirement?
The exact answer depends on the project.
This is why a structural engineer should not be treated as someone who simply stamps a completed drawing after the design is finished.
Where engineering is required, the architectural and structural work need to coordinate.
Some California jurisdictions expressly list structural engineering as a possible supporting document. Tulare County, for example, identifies structural engineering and truss calculations among items that may be required depending on the project.
If your project requires professional engineering review, see our PE Stamp service.
Once the structure is resolved, the next question becomes how the dwelling actually operates.
Electrical, Plumbing and HVAC Plans Make the ADU Functional
An ADU needs more than walls and a roof.
It is an independent living space, so building systems must be coordinated with the architecture.
The electrical plan may identify lighting, receptacles, switches, appliances, panels, service information, and other electrical components required by the project.
The plumbing plan can show fixture locations, water supply, sanitary drainage, water heating, and connections to the existing or proposed utility system.
The mechanical plan addresses heating, cooling, ventilation, equipment locations, and related requirements.
These systems are highly interconnected.
Putting the electrical panel on a wall later needed for a large window can create a coordination problem.
Placing a bathroom far from the practical sewer route can make construction unnecessarily complicated.
Choosing an HVAC system without considering the Energy Code can create another redesign.
That is why utilities and MEP should begin influencing the design before the architectural plans are considered “finished.”
The current California Energy Commission guidance specifically recognizes HVAC, water heating, ventilation, and other energy-related systems as part of ADU compliance considerations.
And that leads directly into one of the most important California-specific parts of the package: Title 24.
Title 24 Is Part of the Permit Strategy, Not an End-of-Project Attachment
“Title 24” is commonly used by homeowners to refer to California energy compliance.
For ADU projects, this is not something we recommend treating as a form to attach after the drawings are complete.
The California Energy Commission’s 2025 Energy Code applies to permit applications submitted on or after January 1, 2026. The update affects new buildings as well as applicable additions and alterations.
The Energy Code treatment of an ADU depends on the project type.
A new detached ADU is treated differently from work that converts or modifies existing space. The CEC specifically distinguishes newly constructed detached ADUs, additions, alterations, JADUs, and conversions when explaining Energy Code compliance.
That matters because energy decisions affect architectural drawings.
Wall and roof assemblies affect insulation.
Windows affect the envelope.
HVAC selection affects compliance calculations.
Water heating affects the energy documentation.
Ventilation affects mechanical coordination.
If Title 24 work is performed only after every architectural decision has been locked, the energy consultant may identify a change that forces the design backward.
The better approach is to coordinate energy requirements while the building design is still being developed.
Hayward’s current ADU permit guidance illustrates how integrated this documentation can become: the city requires professional plan formatting and specifies that Title 24 energy forms be incorporated into the drawing set, while structural calculations may be submitted separately when required.
Utilities Need to Be Considered Before the Permit Set Is Finished
Utility planning is one of the areas most likely to affect an ADU after the floor plan appears complete.
A detached unit may need new connections or extensions for water, sewer, electrical service, and other systems.
A garage conversion may be physically close to existing services but still require upgrades or new routing.
The permit package therefore needs to answer practical questions early.
Where will the sewer connection run?
Is the existing electrical service adequate for the added dwelling load?
How will water reach the unit?
Where will HVAC equipment go?
Does the property rely on septic rather than municipal sewer?
Are utility easements affecting the proposed location?
California jurisdictions may require supporting documentation based on those conditions. Tulare County specifically identifies water and sewer documentation, septic-related Environmental Health approval, Title 24 calculations, structural engineering, and fire-district approval among possible supporting requirements.
Once utility feasibility is understood, the drawing package can be coordinated around actual site conditions rather than assumptions.
Detached ADUs and Garage Conversions Need Different Drawing Strategies
Both projects create an ADU.
They should not be drafted as though they are the same construction problem.
Detached ADU
A detached ADU is new construction.
The package generally starts from a new footprint and coordinates the site plan, architecture, foundation, structural framing, utilities, energy compliance, and MEP systems around that new structure.
The advantage is design freedom.
The challenge is that nearly every building component is new.
Garage Conversion ADU
A garage conversion starts with existing construction.
That can reduce the amount of new exterior structure, but it adds another type of complexity: proving what exists and showing how the existing shell is being converted into compliant living space.
Foundation conditions, wall assemblies, roof framing, garage-door infill, window openings, insulation, utilities, and existing construction all need careful coordination.
The California Energy Commission also distinguishes garage conversions and other changes to existing conditioned or unconditioned space when applying the Energy Code.
This is why “garage already exists” should never be interpreted as “only a floor plan is needed.”
Fire, Separation and Access Can Change the Design Before Submittal
Not every California lot has the same fire or access conditions.
Some projects may need fire-district review, while local site conditions can affect emergency access, separation between buildings, construction details, or other fire-related requirements.
This is another reason a statewide ADU article cannot replace jurisdiction-specific research.
A project in Los Angeles may encounter different parcel conditions and submission processes from one in Salinas, Fresno, Fremont, or another California jurisdiction.
Our California permit site plan hub provides the broader state-level starting point. For projects in LA, our Los Angeles site plan service area covers the city and county permitting environment in more detail.
The important principle is the same throughout the state:
state ADU law establishes the framework, but the permit drawings still need to respond to the actual property and reviewing agency.
Real Project Contrast: Detached ADU Permit Set in Fremont
A good example of this coordination appears in SitePlans.Online’s Fremont project.
The project was an 800-square-foot detached new-construction ADU in Fremont, Alameda County.
Because this was not a site-plan-only project, the permit package had to coordinate the site plan, floor plans, elevations, structural framing, MEP information, Title 24 compliance, and professional engineering on the structural sheets.
The completed package was approved by Fremont Development Services and the ADU moved into construction.
The important lesson is not that every California ADU needs an identical sheet count.
It is that each discipline needs to describe the same building.
The site plan cannot show one footprint while the foundation shows another.
The floor plan cannot show windows that disappear from the elevations.
The structural design cannot assume wall locations different from the architectural design.
The energy documentation cannot use assemblies that do not match the sections.
Coordination is the permit package.
What You Should Send Before California ADU Drafting Begins
The better the starting information, the fewer assumptions need to be made during drafting.
For most projects, we want the project address first because it lets us identify the jurisdiction and begin reviewing parcel conditions.
From there, useful material includes:
- Existing survey or property documents if available
- Photos and basic dimensions of existing buildings, especially garage conversions
- Your preferred ADU size, bedrooms, bathrooms, and general layout
- Existing sketches, contractor concepts, or inspiration plans
- Any city checklist, prior plan review comments, or correction notice already received
You do not need to arrive with a perfect architectural package.
The point is to give the drafting and engineering team enough reliable information to separate known conditions from assumptions.
If the property has not yet been checked for basic ADU feasibility, use the ADU Feasibility Checker before committing to the complete design.
Permit Corrections Are Part of the Workflow, Not Proof the Entire Set Failed
Even a well-prepared ADU set may receive plan-check comments.
That does not automatically mean the design was wrong.
Reviewers may request clarification, updated calculations, additional notation, revised utility information, or jurisdiction-specific details that were not obvious from a general checklist.
The important question is how the corrections are handled.
A correction affecting the architectural plan may also affect structure, MEP, Title 24, or the site plan.
Changing only one sheet can create inconsistencies elsewhere.
We therefore treat correction work as a coordination exercise.
Read the reviewer comment.
Identify every drawing or calculation affected.
Make the change across the set.
Check that no new conflict has been created.
Then resubmit a coordinated package.
This is one reason professional permit drafting is about much more than producing attractive drawings.
California ADU Permit Package: Final Checklist
Before an ADU permit package is ready for submission, we want to be able to answer five questions.
Does the ADU fit the property?
The site plan and feasibility work should support the proposed location.
Does the architecture describe a complete dwelling?
The floor plan, elevations, roof plan, and sections should agree with one another.
Can the proposed or existing structure support the design?
Foundation and structural information should match the architecture, with engineering where required.
Can the dwelling function?
Electrical, plumbing, HVAC, utilities, and access should be coordinated rather than left as future assumptions.
Does the package address current California energy requirements and local submittal requirements?
For applications filed in 2026, the 2025 Energy Code is now the applicable statewide energy standard, while local cities and counties continue to control the permit-submittal process.
If those five questions are answered clearly, the permit set is doing its job.
FAQs
What drawings are normally included in California ADU plans?
A California ADU permit set can include a site plan, existing-condition drawings, proposed floor plans, roof plan, elevations, sections, foundation plan, structural framing, electrical, plumbing, HVAC, utility information, energy documentation, and supporting engineering. The final list depends on the project and jurisdiction.
Does every California ADU need structural plans?
Not every project has identical structural requirements, but new detached construction and garage conversions involving structural changes commonly require structural documentation or engineering. The reviewing building department and project scope determine the final requirement.
Does a California ADU need Title 24?
California ADUs are subject to the state’s Energy Code as applicable to their project type. Permit applications filed on or after January 1, 2026 fall under the 2025 Energy Code.
Is a garage conversion ADU easier to permit than a detached ADU?
It can reduce the amount of new construction because an existing shell is being reused, but garage conversions introduce their own challenges. Existing foundation conditions, structural modifications, new openings, insulation, energy compliance, plumbing, electrical work, HVAC, and fire-related requirements still need to be addressed.
Do I need a site plan for a garage conversion?
A jurisdiction may still require site information even when the exterior footprint already exists because the reviewer needs to understand the property, existing structures, access, utilities, and the relationship of the conversion to the rest of the site. Always follow the specific city’s ADU checklist.
Can I use a pre-approved ADU plan in California?
California jurisdictions now have expanded pre-approved ADU plan programs, but pre-approved plans do not eliminate all site-specific work. Hayward, for example, still requires site-specific construction documents including a site plan and foundation information when a pre-approved design is used.
Who prepares Title 24 documents for an ADU?
Energy compliance documentation is typically prepared using California-approved compliance methods and software. The CEC maintains approved compliance software for the 2025 Energy Code.
Do utility plans have to be included with every ADU permit?
The required utility documentation varies. Water, sewer, septic, electrical service, and other utility conditions can trigger additional information or outside-agency review depending on the property and jurisdiction.
Do California ADU plans need a PE stamp?
Not automatically. A PE stamp becomes relevant when the project includes engineering work or the jurisdiction requires signed and sealed structural or other engineering documentation. The project should be reviewed before assuming either that engineering is unnecessary or that every sheet must be stamped.
What should I do before ordering ADU plans?
Start with the project address and basic concept. Confirm that the property can support the intended ADU, then develop the site and architectural scope before structural, MEP, utility, and energy documentation are finalized.
Check My California ADU Project
If you have decided to build an ADU but do not yet know exactly what the permit set needs, do not start by ordering random sheets.
Start with the property.
Send us the California project address, tell us whether you are planning a detached ADU, attached ADU, garage conversion, or another configuration, and share any existing survey, sketch, city checklist, or previous permit comments you already have.
We can then identify the likely scope and coordinate the site, architectural, structural, MEP, energy, utility, and engineering requirements around one project.
Check your ADU feasibility or review our California ADU permit plan service to get started.
The goal is not to produce more drawings.
It is to produce a permit package in which every drawing supports the same buildable ADU.
