Does remodeling increase property taxes in California? Sometimes. A permit by itself doesn't raise your tax. What matters is whether the county assessor treats the work as "new construction." An addition, a converted garage or a down-to-the-studs rebuild usually is. Painting, new carpet and routine repairs usually aren't, and a few kinds of work are excluded by law even when they add value.
This guide explains where that line falls for common mid-century projects, the four exclusions to know before you build, and when the new value reaches your bill. It's based on the Revenue and Taxation Code, the State Board of Equalization (BOE) new construction page and claim forms, and the San Mateo County Assessor's FAQ, all read on November 6, 2026. Confirm your project with your own county assessor.
New construction, not the permit, is what gets assessed
Revenue and Taxation Code section 70 defines "new construction" for property tax. As of November 2026, it covers any addition to land or improvements, including fixtures, since the last lien date, and any alteration that is a "major rehabilitation" or converts the property to a different use. Section 70(b) says a rehabilitation, renovation or modernization is a major rehabilitation when it converts an improvement or fixture to "the substantial equivalent of a new improvement or fixture."
Only the new part is reassessed. Under section 71, the assessor sets a new base year value for the newly constructed portion, and the base year value of the rest of the property doesn't change. The BOE says the new base year value is "the increment of market value" the work adds, and "The value of the existing property is not affected." So a long-held house keeps its older base year value on the original structure, with a separate value added for the new work.
The BOE says copies of building permits must be sent to the county assessor, but "not every building permit for new construction results in reassessment." It also says the assessor must value all new construction, "even if a building permit has not been issued," and finds it through reports when a property changes ownership, information from the public and routine field checks.
What the BOE lists as new construction, and what it doesn't
Among the improvements the BOE's new construction page lists as new construction:
additions to existing improvements, and increasing the square footage of a residence;
rebuilding after taking an entire house, or a portion of it, down to its foundation and studs;
adding a garage, swimming pool, spa, patio or deck;
upgrading the capacity of plumbing or electrical systems;
converting a garage, unfinished basement or attic into living area;
converting a single-family residence to a residence of two or more units;
kitchen and bathroom work with structural changes, upgraded plumbing or electrical systems, a changed floor plan, a larger room, or cabinets, countertops, flooring or fixtures replaced with upgraded material and finishes.
On the other side, the BOE lists normal maintenance and repairs, and "Painting, re-carpeting and relocating electrical and telephone jacks or lines." Its FAQ adds that replacing a shake roof with a tile roof is not new construction, "since that type of improvement is considered routine maintenance."
The gray area is large. The BOE says rehabilitation "usually is assessable" because it is more structural, and may involve substantial changes to the plumbing, electrical, framing or foundation. A kitchen can be new construction if, in the assessor's opinion, it "is now the equivalent of a new kitchen," but not if the work is remodeling or maintenance. The BOE says the assessor decides both questions case by case.
San Mateo County's assessor says the same in its real estate FAQ: kitchen and bath remodels are "determined on a case-by-case basis," and like-for-like replacement or maintenance "would not qualify as new construction." It also says an addition "is considered new construction, which the county may reassess," and that adding a bathroom, room or loft within existing space "is considered a change in use which is reassessable."
Common mid-century projects, mapped to those examples
Your assessor makes the call, but here is how typical Eichler and post-and-beam projects line up with those examples.
Enclosing a carport or atrium for living space. Converting a garage into living area and adding square footage are both on the BOE's new construction list.
A teardown that keeps one wall. The BOE says leaving one wall standing "would make no difference for property tax purposes"; the new house would be new construction in its entirety. San Mateo says the same of leaving "a corner or wall standing."
A bigger electrical service. The BOE's new construction list includes "upgrading the capacity of plumbing or electrical systems." Ask your assessor whether a panel or service upgrade on your house falls under that line. Our guide to the mid-century electrical panel and wiring covers the work itself.
Decks, patio covers and pools. The BOE's valuation FAQ names patio covers, pools, spas, decks, sunrooms and flatwork as additions that cause a reassessment of the newly built portion.
Four exclusions to know before you build
As of November 2026, these exclusions come up on a house, even when the work adds value:
Fire sprinklers, alarms and fire-related exits (section 74)
Section 74 excludes a fire sprinkler system, other fire extinguishing system, fire detection system or fire-related egress improvement installed on or after November 7, 1984, including a sprinkler system fed by the building's domestic water supply. Under section 74(e), it applies only to systems installed in an existing building. The BOE's exclusions table lists no form for it.
Seismic retrofitting (section 74.5)
Section 74.5 excludes the portion of an existing structure that consists of seismic retrofitting components, but not new plumbing, electrical or finishing materials added alongside the seismic work. The owner, primary contractor, civil or structural engineer, or architect certifies to the building department which parts are seismic, and the building department reports their cost to the assessor. Notify the assessor before, or within 30 days of, completion, and file supporting documents within six months. The claim is the BOE-64, Claim for Seismic Safety Construction Exclusion from Assessment; the BOE's sample (Rev. 12, 07-25) says to get the actual form from your assessor. Our guide to the post and beam earthquake retrofit explains what a slab-built house may need.
Accessibility changes (section 74.3)
Section 74.3 excludes work on an existing dwelling that is eligible for the homeowners' exemption, when the work makes it more accessible to a severely and permanently disabled person who is a permanent resident. It can cover a new addition, such as a bedroom or bath, that duplicates existing facilities the resident can't use solely because of the disability. Only the features that specially adapt the dwelling are excluded, not other improvements made at the same time. It doesn't apply to an entirely new dwelling, and covers work completed on or after June 6, 1990. The claim, BOE-63, needs a statement from a licensed physician or surgeon and a statement identifying the work, and the statute lets the assessor charge a processing fee.
Active solar energy systems (section 73)
As section 73 reads in November 2026, it applies to lien dates through the 2025–26 fiscal year and remains in effect only until January 1, 2027. Systems that qualify before that date stay excluded until a change in ownership. If your system will be finished in late 2026 or later, ask your county assessor how the exclusion applies before you count on it. Permits for the system are covered in our solar permit guide.
The BOE's table gives all four exclusions the same time limit: "Until establishment of new base year value." The BOE-64 says the seismic exclusion "EXPIRES UPON CHANGE IN OWNERSHIP OF THE PROPERTY," and section 73(f) says the same for solar. Separately, section 70(c) says timely reconstruction after a misfortune or calamity isn't new construction when the rebuilt property is substantially equivalent to what was lost.
When the new value reaches your tax bill
Under section 75.10, the assessor appraises completed new construction at its full cash value on the completion date, and that value becomes its base year value. The BOE says the completion date "is the date the property or portion thereof is available for use." If work is still underway on a January 1 lien date, section 71 has the assessor value it at its full value on that date and each lien date after, without giving it a base year value until it's done.
Completed new construction can also bring a supplemental assessment and a separate bill. Our guide to supplemental property tax in California explains how that bill is prorated and paid.
A checklist before the work starts
Describe the project to your county assessor and ask whether it will be treated as new construction, maintenance or remodeling.
Ask your engineer or contractor to separate seismic, fire sprinkler and other excluded items in the plans and the cost breakdown.
For seismic work, calendar the BOE-64 notice (before, or within 30 days of, completion) and the six-month document deadline.
For a solar system, ask your assessor how section 73's January 1, 2027 date applies to your completion date.
Set aside money for a supplemental bill after completion.
This is general information as of November 2026, not legal or tax advice. Check with your county assessor, a tax advisor or an attorney about your own project.
Frequently asked questions
Will a kitchen remodel raise my property taxes?
It depends on the scope. The BOE says a kitchen can be new construction if the assessor finds it "is now the equivalent of a new kitchen," but remodeling or maintenance doesn't qualify. If it is new construction, only the value the work adds is assessed.
Does a new roof raise property taxes in California?
Usually not. The BOE's FAQ says replacing a shake roof with a tile roof is not new construction because it's considered routine maintenance. Adding square footage under a new roof is a different matter.
Do fire sprinklers raise property taxes?
Not when they're added to an existing building. Revenue and Taxation Code section 74 excludes fire sprinkler, extinguishing and detection systems and fire-related egress improvements installed on or after November 7, 1984, and the BOE lists no claim form for it.
Related reading
California Homeowners' Exemption: How to Claim It After You Buy
Prop 8 Decline in Value: Asking the Assessor for a Lower Value
Hire a Licensed Contractor in California: Mid-Century Remodel Guide
More guides on this topic: Owning & Renovating a Mid-Century Modern Home
Planning an addition or a major remodel on a mid-century home? Call or text the Boyenga Team at Compass at (408) 373-1660 or (650) 383-8606, or contact the Boyenga Team to talk it through.
