ADU permit drawings: what goes in the set
An accessory dwelling unit, or ADU, is a second, smaller home on the same lot as a house: a backyard cottage, a unit added onto the house, or a garage or basement converted into its own apartment. Because it is a complete home, the permit set is closer to a small new house than to a remodel. Here is what goes in it.
Updated 2026-10-19. ADU rules are set by each state, city and county; this page describes the drawings most departments ask for, not the rules of any one place. Check the submittal checklist your building department publishes.
The three kinds of ADU
- Detached. A new building in the yard. It needs the full set below, including foundation and structure.
- Attached. An addition to the house with its own entrance. The plans show the existing house wall and how the two connect.
- Conversion. A garage, basement or other existing space made into a unit. The set starts with an existing plan of that space, then shows the changes. See our garage conversion guide for the room rules.
California also allows a junior ADU of up to 500 sq ft inside a single family house.
What goes in the permit set
| Sheet | What it shows |
|---|---|
| Site plan | Lot lines, every existing building, the ADU footprint, distances to property lines, and where water, sewer and power run |
| Floor plan | Every room with its size, doors, windows, kitchen and bathroom fixtures |
| Elevations | Each outside face with heights, windows and materials |
| Sections | A cut through the building showing floor, wall and roof build up and ceiling heights |
| Roof plan | Slopes, drainage and roof material |
| Foundation and framing | Footings, beams, shear walls; for new construction many departments ask for calculations from a licensed engineer or architect |
| Electrical, plumbing, mechanical | Panel and circuits, fixture and drain layout, heating and cooling |
| Energy compliance | The forms your state energy code requires; in California these are the Title 24 energy forms |
Preapproved and permit ready plans
Many cities, especially in California, publish ADU plans they have already reviewed. You pick one, add your own site plan, and the review is shorter because the building itself was checked before. California law (AB 1332, in effect since January 1, 2025) requires every city and county to run a program that reviews ADU plans in advance and posts the approved ones on its website. California also requires a city or county to approve or deny a complete ADU permit application within 60 days when the lot already has a house or apartment building on it. You can read the text of AB 1332 on the state legislature site.
A preapproved plan still needs a site plan for your lot, and a conversion still needs drawings of the space you are converting, because no stock plan knows your garage.
Order of work
- Read the local rules. Size limits, setbacks, height and parking for ADUs, from your city or county planning department.
- Measure what exists. For a conversion or attached unit, an accurate plan of the existing space and walls.
- Choose the design. A preapproved plan, or a custom design by a designer, architect or engineer.
- Complete the set. Site plan, structure, energy forms and utilities, per the department checklist.
- Submit and answer comments. Reviewers send corrections; the designer revises and resubmits.
Where we fit
We draw the 2D floor plan of the existing space, such as the garage or basement you plan to convert, from your measurements and photos. That is the existing conditions sheet a designer builds the ADU set on. The first plan is free with FIRSTPLAN and each extra plan is $10. We do not prepare full ADU permit sets.
Free first 2D floor plan
New customers get one 2D floor plan of one floor of their home free, one per new customer. Use the code FIRSTPLAN on the quote form.
- What you send: the room measurements of that floor (a hand sketch with numbers is fine) and photos of each room.
- What you get: an as-built 2D floor plan of that floor as a PDF, drawn from your measurements.
- When: usually within 5 US business days after we have your measurements and photos. If we are behind, we tell you the date before we start.
- No card, nothing to pay, no obligation to order anything else.
- More plans: first plan free with FIRSTPLAN, each extra plan $10 (another floor or another property).
A plan drawn from your measurements is not a survey, an engineered design or a permit approval. Your building department decides what it accepts. We are not architects or engineers and do not stamp drawings.