Underwriters look past the year built to what has been replaced since: wiring, plumbing, roof, heating, foundation and the sewer line. A 1920s house with a newer roof, updated wiring and replaced pipes reads very differently from one with original systems, and permits and invoices are how you prove it. The other half is the limit. An older home should be insured for what it would cost to rebuild to today’s code, not its sale price, and building code upgrade coverage is designed to pay the code-driven extra. If regular carriers decline, surplus lines or the FAIR Plan with a difference in conditions policy are the usual routes.
What underwriters ask about
On an older house I get asked about each major system and when it was last updated, and the answers decide which homeowners carriers will quote the house at all.
- Electrical. The type of wiring, the panel, and whether the service has been upgraded.
- Plumbing. What the supply lines and drains are made of (galvanized steel, polybutylene, cast iron, copper or PEX) and when they were replaced. With original pipes, the question is water damage.
- Roof. Material and age. How an older roof affects coverage.
- Heating. What heats the house and when it was installed.
- Foundation. Slab or raised, and whether a raised foundation has been bolted and braced.
- Sewer lateral. The line from the house to the street main, and whether it has been inspected or replaced. Whether sewer backup is covered is a separate question.
Knob-and-tube and aluminum wiring
A U.S. Department of Energy weatherization notice explains the knob-and-tube concern: it was meant to be cooled by free air moving around it in walls and attics, and laboratory tests have shown that adding insulation around it can make it overheat. If insulation was ever blown in over it, say so and have an electrician look before you apply.
On aluminum branch wiring, the Consumer Product Safety Commission says a mid-1960s copper shortage pushed builders toward it: homes built before 1965 are unlikely to have it, and cable installed between 1965 and the mid-1970s may contain it. A survey done for CPSC found pre-1972 aluminum-wired homes were 55 times more likely than copper-wired homes to have one or more outlet connections reach “Fire Hazard Conditions.” As of its June 2011 edition, CPSC’s repair guide approves only three permanent repairs: replacing the aluminum branch circuits with copper, the COPALUM crimp method, and the AlumiConn connector. An electrician’s invoice showing one of them is the record to keep.
How to document updates
Showing the work beats describing it. Before you shop, gather:
- Permits with final sign-offs for electrical, plumbing, roofing and seismic work; your building department may have copies.
- Contractor invoices showing what was done, to which system, and when.
- Inspection reports from your purchase, plus any sewer lateral camera inspection.
- Dated photos of the electrical panel, water heater strapping, roof and crawl space.
In the areas under the East Bay’s Regional Private Sewer Lateral Ordinance (Alameda, Albany, Emeryville, Oakland, Piedmont, Kensington, El Cerrito and Richmond Annex), an EBMUD compliance certificate showing a leak-free lateral is required to close escrow on a sale and for final permit sign-off on building or remodeling work over $100,000. If you have one, include it.
Raised foundations and earthquake retrofits
On a raised foundation, the underwriter will want to know whether the house has been retrofitted. The Earthquake Brace + Bolt program, run by the California Residential Mitigation Program with money from the California Earthquake Authority’s Loss Mitigation Fund and FEMA’s Hazard Mitigation Grant Program, helps pay for that work on wood-frame houses built before 1980 with raised foundations: bolting the frame to the foundation, bracing cripple walls with plywood or OSB sheathing where needed, and strapping the water heater. The retrofit and an earthquake policy are separate decisions.
Insure the rebuild, not the sale price
The sale price of an older home reflects the lot and location; the dwelling limit has to cover construction. California’s required residential disclosure describes replacement cost as the cost to repair or replace the dwelling without a deduction for depreciation, and Insurance Code 2051.5 caps that payment at the policy limit. Rebuilding an old house means meeting today’s codes, not the original ones.
That code-driven extra is what building code upgrade coverage, also called ordinance or law coverage, is designed to pay: the additional cost to repair or replace the dwelling to comply with building codes and zoning laws in effect at the time of loss or rebuilding. Under Insurance Code 10103.4, insurers providing replacement cost coverage generally must give you a rebuild estimate every other year at renewal, but choosing the limit is on you. See what drives rebuild cost in California, the rebuild cost estimator, and extended vs. guaranteed replacement cost.
Historic homes and the Mills Act
A Mills Act contract is between you and your local government, not your insurer. According to the California Office of Historic Preservation, owners agree to restore, maintain and protect the property to historic preservation standards for at least ten years in exchange for a property tax valuation based on the income approach, and the contract carries over to new owners when the property is sold. It doesn’t change your policy, but tell me about it: a rebuild estimate based on ordinary modern construction may not reflect what restoration would take.
If regular carriers say no
- Surplus lines. Non-admitted insurers can write houses the standard market passes on. California law requires you to sign a notice that the insurer is not a California-admitted company, is not subject to the financial solvency regulation that applies to admitted insurers, and is not backed by California’s guarantee funds if it becomes insolvent. CDI publishes its list of approved surplus line insurers (LASLI).
- FAIR Plan plus DIC. The California FAIR Plan is for owners who can’t get coverage from a regular insurance company, and its policy is limited. A difference in conditions policy is added for perils such as water damage, theft and liability that the FAIR Plan doesn’t currently cover. How the FAIR Plan and DIC fit together.
Fixing what triggered a decline, such as aluminum wiring or an old roof, can reopen the standard market.
Common questions
Can I insure a house with knob-and-tube wiring?
It depends on the carrier, and you should expect to be asked about it. An electrician’s evaluation, and confirmation that insulation wasn’t added around the wiring, gives an underwriter something to work with; replacing it widens your options.
Should I insure an older home for its market value?
No. The dwelling limit should reflect the cost to rebuild to current code. Market value includes the land, so it can be well above or below that number.
Does a Mills Act contract affect my homeowners insurance?
Not directly. It’s a property tax agreement with your local government. Your policy is separate, but preservation commitments are worth factoring into the rebuild limit.
What proof of updates do insurers want?
Permits with final sign-offs, contractor invoices, and dated photos of the panel, plumbing, roof and foundation work. Keep them in one place so they can go with the application.
What’s different about a surplus lines policy?
The insurer isn’t a California-admitted company, isn’t subject to the state’s solvency regulation for admitted insurers, and California’s guarantee funds won’t pay claims if it becomes insolvent. You sign a notice saying so.
Sources
- California Insurance Code 10102: residential property insurance disclosure (replacement cost, building code upgrade coverage)
- California Insurance Code 2051.5: measure of indemnity under replacement cost policies
- California Insurance Code 10103.4: replacement cost estimates at renewal
- California Insurance Code 1764.1: surplus line insurer disclosure notice
- U.S. Consumer Product Safety Commission, Publication 516 (June 2011): Repairing Aluminum Wiring
- U.S. Department of Energy, Weatherization Program Notice 02-5 (effective July 12, 2002; archived): Health and Safety Guidance, knob-and-tube wiring
- California Residential Mitigation Program: Earthquake Brace + Bolt retrofit (eligibility, funding, retrofit work)
- California Office of Historic Preservation (California State Parks): Mills Act Program
- California Department of Insurance: California FAIR Plan
- California Department of Insurance fact sheet: Summary on Residential Insurance Policies and the FAIR Plan (2020–2022 policy data; updated June 21, 2024)
- California Department of Insurance: List of Approved Surplus Line Insurers (LASLI)
- East Bay Municipal Utility District (EBMUD): Private sewer laterals and Compliance Certificates
- East Bay Regional Private Sewer Lateral Program (EBMUD program site): Regional PSL Ordinance, affected areas and triggers
General information about insuring older homes in California as of October 2026, not legal or tax advice; the California Insurance Code, your policy wording and each insurer’s underwriting rules control. Coverage depends on underwriting and the terms, conditions and exclusions of the policy actually issued.