Journal ·
Building an ADU in Burbank: What Actually Gets Reassessed
Building an accessory dwelling unit in Burbank does not reassess your house. The assessor gives the new unit its own base year value and leaves the rest of the property where it was, however long you have owned it. One sentence of state law does that work, and it is worth reading before a contractor quotes you a number.
Does an ADU trigger reassessment of the whole property?
No. Revenue and Taxation Code section 71 provides that the assessor determines a new base year value for the portion of property that has been newly constructed, and that "the base year value of the remainder of the property assessed, which did not undergo new construction, shall not be changed."
A house bought in 1994 keeps its 1994 base, adjusted by the annual inflation factor. The ADU is valued at completion and added on top. The two live side by side on the same parcel and on the same tax bill.
The section also handles the years while the work is happening. Construction in progress on the lien date is appraised at its full value on that date and each lien date after it, until completion. It does not acquire a base year value each January. Only the finished unit does.
| What happens | What it does to your assessment |
|---|---|
| ADU completed | New base year value for the ADU only |
| Existing house, untouched | No change to its base year value |
| ADU under construction on a lien date | Appraised at full value that year, no base year value set |
| Kitchen or bath remodel in the main house | Repair and maintenance, not new construction |
| Garage converted to living space | New construction, because the use changed |
What counts as new construction in the first place?
Section 70 defines it in two parts. The first is any addition to land or improvements since the last lien date. The second is any alteration since the last lien date that constitutes a major rehabilitation or that converts the property to a different use.
Subdivision (b) supplies the test for the second part. A rehabilitation, renovation or modernization is a major rehabilitation where it converts the improvement to "the substantial equivalent of a new improvement."
That phrasing is why a garage conversion is treated differently from a new bathroom. Replacing fixtures in a room that was already a bathroom changes nothing about its use. Turning storage into a dwelling with a kitchen changes the use of that space, and the converted portion picks up a new base year value. Only that portion.
How does the assessor find out?
The city tells them, and the mechanism is more thorough than most owners expect. Section 72 requires every permit issuing entity to transmit a copy of any building permit to the county assessor as soon as possible after issuance. It then requires a copy of the certificate of occupancy, or any other document showing the date of completion, within 30 days of issuance or finalization.
Subdivision (c) goes further. When approved building plans are filed, the applicant must also file a scale copy of the floor plans and exterior dimensions designated for the assessor, in enough detail for the assessor to work out the square footage and, for a residential building, "the intended use of each room."
So the assessor receives your floor plan, room by room, before the first inspection. There is no version of this where the unit is built quietly and noticed later.
When does the bill arrive and how much is it?
Not with your annual bill, and not through your lender. Completion produces a Notice of Supplemental Assessment and then one or two prorated bills. The California State Board of Equalization publishes the proration factors and a worked example built on exactly this fact pattern: a bedroom and bathroom addition completed in October, valued at $39,000, produced a single supplemental bill of $268 at an illustrative 1.025 percent rate.
The timing rule is mechanical. Completion between June and December produces one supplemental bill covering the rest of that fiscal year. Completion between January and May produces two, the second covering the full following year. The wider explanation sits in the supplemental property tax bill explainer.
What are Burbank's own limits on ADU size?
The city publishes them through the Burbank Preapproved ADU Program, which the program page attributes to Assembly Bill 1332 and describes as a route to permit issuance in 30 days using preapproved plans.
The caps in the program's own frequently asked questions:
- 850 square feet for a studio or one bedroom unit, and up to 1,000 square feet for two bedrooms, absent special zoning requirements.
- A Very High Fire Hazard Severity Zone parcel is limited to 800 square feet with no exceptions.
- The Rancho area allows no new ADU construction at all. The equestrian overlay has its own logic, covered in the R-1-H horsekeeping rules.
- The program covers new construction only. Garage conversions are excluded from it, which does not make them illegal, only outside the preapproved route.
- Preapproval expires with the triennial California building standards code cycle, and the page notes the next cycle starting January 1, 2026.
As of the program page reviewed on 31 August 2026, the BPAP Library lists a single accepted plan, BPAP 24001, a 432 square foot one story studio. Zoning and siting questions run through Burbank's own ADU rules rather than through the assessor.
Why does the city look up your assessed square footage?
Here is where the tax record and the permit counter meet, and it surprises people who assume the two offices never speak.
Burbank's program page states that under Senate Bill 13, accessory dwelling units over 750 square feet may be charged a proportional percentage of current development impact fees. To calculate that proportion, the page says the city reviews the Los Angeles County Assessor's records for the assessed square footage of the primary dwelling. On a multifamily lot it uses the average square footage per unit instead.
The consequence is concrete. If square footage was ever added to the main house without a permit, the assessor's figure is lower than the house actually is, and the ratio used for your impact fee is calculated against that lower figure. The page also notes that unless a permit for the primary dwelling has reached final inspection, additional square footage is not included in the percentage calculation at all. Two owners with identical ADUs can pay different fees because of what the county already has on file.
What if the ADU replaces something that burned or fell down?
Section 70(c) treats that separately. Where real property has been damaged or destroyed by misfortune or calamity, timely reconstruction that leaves the property substantially equivalent to what stood before is not new construction. Reconstruction that goes beyond substantially equivalent is new construction, and only the portion that exceeds it receives a new base year value.
The words doing the work are "timely" and "substantially equivalent." Neither is defined by a number in the section, and both are questions for the assessor on the facts of the specific property.
Q: Will renting out the ADU change my assessment?
Renting is not a change in ownership and not new construction. The assessment follows the physical unit and the base year value, not the occupancy.
Q: Does the homeowners' exemption cover the ADU?
The exemption attaches to the dwelling occupied as a principal residence. It is not multiplied by adding a second unit, and it does not transfer to the ADU if you continue living in the main house.
Q: My neighbour built an ADU and their taxes barely moved. Why is mine higher?
The added value is the market value of what was built, at completion. Size, finish level and the month of completion all move the number, and the proration factor for a completion in May differs sharply from one in July.
Q: Do I need to file anything with the assessor myself?
Section 72 puts the transmission duty on the permit issuing entity, not on you, apart from the scale floor plans filed with the plans themselves. Your obligation is at the permit counter.
This article is general information about California statutes and published Burbank program materials, not legal or tax advice. Program requirements change, and the Burbank Building Division at (818) 238-5220 is the office that confirms them. Call Alla at (818) 699-5367 or use the enquiry form.
More on buying and building in this market in the Burbank area guide.