Buying a Historic Home in California: Designation, Mills Act and Inspections

By Matthew Martinez, Founder, CEO & Managing Broker, Diamond Real Estate Group. California DRE #01869679.

Buying a historic home in California mostly comes down to three questions: is the property locally designated, and what review applies to exterior changes; does it carry a Mills Act contract that binds you as the next owner; and what will an older house need in inspections, insurance and code work. Local rules matter most. A city landmark or historic district usually means design review for exterior work, while a National Register listing on its own often doesn’t. Check the city or county planning department before you remove contingencies.

This guide walks through each layer, with lookup tools for some of the places we serve. For the Mills Act alone, our Mills Act guide for Bay Area historic homes goes deeper on local programs and deadlines.

The layers of "historic"

"Historic" can mean several different things, and each has different consequences.

Sources: Gov. Code §50281, Health & Safety Code §18955, SF Planning Code §1006, California OHP Mills Act page.

Local designation and design review

Most of the day-to-day rules for a historic house come from the city or county, not the state. Ordinances differ, but the pattern is similar: if a property is a designated landmark or sits in a historic or preservation district, exterior work that needs a building permit also needs historic review, and demolition is tightly controlled. Interior work and ordinary repairs are often handled more simply.

Here’s how that looks in a few places we serve, based on the official pages we reviewed:

• San Francisco. Under Planning Code Section 1006, work on an Article 10 landmark site or in an Article 10 historic district that needs a City permit generally requires a Certificate of Appropriateness. The section lists work the Planning Department can process without further Article 10 review, including interior-only changes that don’t significantly affect the exterior and ordinary maintenance and repairs. Where a district’s designating ordinance says so, some visible exterior changes, such as painting or landscaping, need approval even without a permit. The Planning Department’s Property Information Map has a Historic Preservation section showing Article 10 and Article 11 designations, register listings and Mills Act properties. The city calls that status "tentative" and suggests confirming with a Preservation Technical Specialist at 628.652.7300 or pic@sfgov.org. For housing styles, see our guide to San Francisco Victorian and Edwardian homes.
• Santa Rosa. The city’s Historic (-H) combining district rules cover every property in a designated preservation district, contributing or not, plus locally designated landmarks. Approval of a Landmark Alteration Permit requires a finding of consistency with the Secretary of the Interior’s Standards for Rehabilitation. Our Santa Rosa historic homes guide covers the districts and what needs a permit.
• City of Sonoma. Under Sonoma Municipal Code §19.80.060, the city’s historic preservation commission initiates, reviews and designates local historic resources and districts. See our post on remodel approvals and records for Sonoma historic homes.
• Santa Cruz County (unincorporated). The county keeps a Historic Inventory. Its Mills Act page points to the county’s designated historic resources page and GIS property search for checking a parcel.

For other cities and counties, call the planning department, give them the parcel number, and ask three things: Is the property a designated landmark, in a historic district, or on a local survey? What review applies to exterior changes, windows, roofing, additions and demolition? Are there pending designations nearby?

Why it matters before you write an offer

If you’re planning a second story, new windows, a solar array, an ADU or a big kitchen addition, design review can shape what’s allowed and how long approval takes. Build time for a planning conversation into your inspection contingency. Ask the seller for any past permits and approvals and keep them with your closing file.

Mills Act contracts

The Mills Act lets a city or county sign a contract with the owner of a qualified historical property. The owner agrees to preserve the property, and in return the county assessor values it under a special income-based method. Key points from Government Code section 50281 and the state Office of Historic Preservation (OHP):

• Term. At least 10 years, renewing automatically each year.
• Standards. Restoration and rehabilitation must follow OHP rules, the Secretary of the Interior’s rehabilitation standards and the State Historical Building Code.
• Inspections. The city or county inspects the interior and exterior before a new contract and every five years after.
• It runs with the property. The contract binds all successors in interest, so a buyer takes on the same duties as the seller.
• Local choice. Each city or county decides whether to offer contracts, sets its own criteria and limits the number of contracts. OHP doesn’t administer the program.

How it affects property tax

According to the Board of Equalization’s general guidance on historical property, a restricted historical property is assessed each year at the lowest of its factored base year value, current market value, or restricted value. The restricted value uses income capitalization: a fair rent, minus ordinary and necessary expenses, divided by a capitalization rate set by formula rather than drawn from the market. That rate adds together an interest component the BOE sets each year, a risk component (2%, or 4% for owner-occupied property), a property tax component and an amortization component for the improvements.

What this means for you depends on the property and the county, so don’t assume a figure. Ask the county assessor how they’ll value the home after your purchase, and ask the city or county for the recorded contract and its required work program. Our Prop 13 guide explains the normal reassessment on a sale.

The California Historical Building Code

The California Historical Building Code (CHBC) is Title 24, Part 8. The Division of the State Architect describes it as applying to qualified historical buildings and structures. The 2025 edition of Title 24 took effect January 1, 2026, according to the Building Standards Commission. Check the current edition with your building department.

Under Health and Safety Code section 18955, a qualified historical building is one a local or state jurisdiction considers important to an area’s history, architecture or culture, including listings on official national, state or local registers. Section 18954 requires local building departments to apply the alternative standards to repairs, alterations and additions that meet the code.

In practice, the CHBC can give your architect or contractor more flexibility than standard code when they’re preserving original materials. It’s not a blanket exemption, and accessibility alternatives are decided item by item. Ask the building department early whether the home qualifies.

Inspections for an older home

Historic homes reward careful inspection. Beyond a general home inspection, buyers often consider:

• Foundation and seismic. Older foundations, cripple walls and chimneys deserve a structural engineer’s look.
• Wood-destroying pests. Read the Section 1 and Section 2 termite report carefully. Older framing and siding can hide damage.
• Electrical, plumbing and sewer. Ask a licensed electrician and plumber to check older wiring, supply lines and the sewer lateral.
• Lead-based paint. For homes built before 1978, federal rules require the seller to give the EPA pamphlet and disclose known lead-based paint. The buyer gets a 10-day opportunity for an inspection or risk assessment, which the parties can change or the buyer can waive in writing. See our lead-based paint disclosure guide.
• Roof, windows and historic features. Ask a contractor familiar with local design review what replacing original windows or roofing would take.

If you’re planning big repairs, a renovation loan may help. Plan time for design review approvals.

Insurance considerations

Older homes can cost more to rebuild with matching materials. The California Department of Insurance’s residential insurance guide warns that not every policy includes building code upgrade (ordinance or law) coverage. Without it, the insurer may not pay to bring a rebuilt home up to current code. The guide also explains the difference between actual cash value and replacement cost. Ask agents to quote both, and ask how they’d handle historic materials. Get quotes early, using our guide to homeowners insurance during escrow.

If you’re searching for a home with character and history, we can help you pull designation and permit records before you write an offer. Contact us to talk through a specific property.

Questions people ask

How do I find out if a house is historic in California?

Call the city or county planning department with the address or parcel number. In San Francisco, the Planning Department’s Property Information Map shows designations. The city calls that status tentative and suggests confirming with staff.

Does a Mills Act contract transfer to the buyer?

Yes. Government Code section 50281 says the contract binds all successors in interest, and OHP confirms that later owners have the same rights and obligations.

Can I get a Mills Act contract after I buy?

Only if your city or county offers the program and the property qualifies. Each local government sets its own criteria, deadlines and limits. Our Mills Act guide lists programs we confirmed.

Do I need permission to paint a historic house?

It depends on the ordinance. In San Francisco, Planning Code Section 1006 lets a district’s designating ordinance require approval for visible exterior changes like painting, even without a permit. Ask your local planning staff.

Is a National Register listing the same as local landmark status?

No. In San Francisco, the Article 10 Certificate of Appropriateness process applies to city landmarks and historic districts. Other cities have their own rules, so confirm locally.

Does the Historical Building Code mean I can skip modern code?

No. It offers alternative standards for qualified historical buildings, applied by the local building department. Accessibility alternatives are decided item by item.

Will insurance cover rebuilding a historic home to its original look?

That depends on your policy. The California Department of Insurance notes that building code upgrade coverage isn’t in every policy, and that replacement cost and actual cash value pay very differently.

Sources & notes

1. California Government Code §50281 (Mills Act contract provisions; Article 12 starts at §50280). Official text: leginfo. Reviewed through a public statute mirror.
2. California Office of Historic Preservation, Mills Act Program.
3. Board of Equalization, historical property general guidance. The interest component changes each year; check the BOE’s current letter to assessors.
4. Health & Safety Code §18955 and §18954. Official text: leginfo §18955.
5. DGS Division of the State Architect, California Historical Building Code; Building Standards Commission, Codes.
6. San Francisco Planning Code §1006; SF Property Information Map.
7. Santa Rosa, Historic (-H) combining district.
8. Sonoma Municipal Code §19.80.060.
9. Santa Cruz County, Mills Act Program.
10. U.S. EPA, Real Estate Disclosure (lead).
11. California Department of Insurance, Residential Property Insurance Guide.

Other local programs weren’t reviewed for this page; confirm designation and review rules with the city or county.

General information, not legal, tax or lending advice. Updated November 2026. Primary sources are linked in this guide.

Related: Mills Act guide · Santa Rosa historic homes · San Francisco Victorian and Edwardian homes