Knob and tube wiring in a San Francisco home sale is no longer something a buyer or seller can quietly ignore. Starting January 1, 2026, California law requires sellers of single-family homes to formally disclose that outdated wiring, including knob and tube wiring, may pose a fire risk and may make it harder to obtain property insurance. For a city where a large share of the housing stock predates the 1950s, that single legal change has turned an old wiring type into a front-and-center part of nearly every real estate transaction.
Whether you are preparing to list a home or you are house hunting in one of San Francisco’s older neighborhoods, knowing how to spot knob and tube wiring, and what to do once you find it, can save you from a stressful surprise late in escrow. It can also save you money, since the earlier this gets addressed, the more control both a buyer and a seller have over cost, timeline, and how the conversation gets negotiated.
The New Disclosure Law Behind This
The requirement comes from Senate Bill 382, authored by State Senator Josh Becker and signed into law in 2024. Under the statute, sellers of single-family residential property must deliver a written disclosure stating that it may be advisable to have a qualified professional inspect the building’s electrical systems, including the main panel, subpanels, and wiring, and that substandard or faulty wiring may cause a fire risk and may make it difficult to obtain property insurance. According to legal resources summarizing California’s disclosure framework, this sits alongside the state’s existing Transfer Disclosure Statement requirements under Civil Code Section 1102, which already ask sellers to flag known defects in a home’s electrical system.
In practice, this means every San Francisco seller now has to put the insurance question in writing, even if their home has never had an electrical problem. That single sentence is often what prompts a buyer to ask deeper questions, or to order their own inspection, before deciding whether to move forward.
A few details of the law are worth understanding clearly. It applies to sellers of single-family residential property, which under California’s Business and Professions Code also covers condominiums, units in a planned development, and stock cooperatives sold through a real estate broker. Certain transfers are exempt, including probate sales, foreclosures, and court-ordered transfers, though agents and sellers should confirm any exemption applies before assuming it does. The disclosure itself does not require the seller to have the electrical system inspected before listing, only to advise the buyer that an inspection may be advisable. That distinction matters: the law creates the prompt, but it leaves the decision about whether to actually get an inspection, and when, up to the buyer and seller involved.
How to Recognize Knob-and-Tube Wiring in an Older Home
You do not need to be an electrician to spot the basic signs of knob and tube wiring during a walkthrough. According to the International Association of Certified Home Inspectors, a few visual clues are usually enough to raise the question, even before a licensed electrician confirms it.
If you notice any of these during a walkthrough, that is a reason to ask questions, not necessarily a reason to walk away. Plenty of San Francisco homes with knob and tube wiring are perfectly livable, and the real issue is simply making sure the wiring’s condition and extent are documented before a purchase, not after. A home with a small amount of inactive knob and tube wiring tucked in an unused attic space is a very different situation from a home where it still feeds outlets and fixtures throughout, and that difference is exactly what a proper inspection is meant to sort out.
What Buyers Should Do Before Closing
If a home inspection turns up knob and tube wiring, the next step is a dedicated electrical evaluation, not just a general home inspector’s note in a broader report. A general inspector can usually tell you knob and tube wiring is present, but a licensed electrician is who can tell you how much of it is still active, where it runs, and what it would take to bring the home fully up to modern standards. That distinction matters for negotiating a repair credit, planning a post-purchase budget, and for your own insurance search, since most carriers will want the same electrician-level detail before they will quote a policy.
It is also worth asking the seller directly whether they have already had an insurance carrier flag the wiring, since that history often reveals more than the disclosure form alone. A seller who has already been denied or non-renewed over knob and tube wiring knows exactly what a buyer is about to face, even if the disclosure statement itself is written in general terms.
Buyers should also factor timing into their contingency period. Scheduling a licensed electrician’s inspection takes coordination, and if the findings are significant enough to negotiate over, that negotiation itself takes time. Building a few extra days into the inspection contingency for exactly this scenario is far less stressful than trying to compress an electrical evaluation, a contractor quote, and a negotiation into the final days before a contingency deadline expires.
“Buyers often assume a general home inspection covers the electrical system completely, but a visual inspection can only tell you so much. If knob and tube wiring shows up in a report, get an electrician in before you finalize anything, not after.”
– Marco, High Voltage Electrical
What Sellers Should Do Before Listing
For sellers, the smartest move under the new disclosure requirement is to get ahead of the question rather than let a buyer’s inspector raise it first. A pre-listing electrical inspection gives you a documented, current answer about your home’s wiring, which does two things at once. It lets you decide whether to address the wiring before listing, and it gives you something concrete to hand a buyer if the topic comes up, rather than relying on the disclosure form’s general language alone.
Sellers who wait until a buyer’s inspection flags the wiring midway through escrow tend to lose leverage in the negotiation. At that point, the buyer has already found a problem, the clock is running on contingency deadlines, and rush scheduling for electrical work often costs more than the same project would have on a normal timeline. Handling it before the home goes on the market keeps the seller in control of both the cost and the timeline.
There is also a simple negotiating logic to this. A repair credit requested by a buyer’s agent, based on a rushed estimate obtained under contingency-deadline pressure, is often higher than what the same work would actually cost on a normal schedule. Sellers who bring their own recent inspection and, where relevant, their own contractor quote to the table tend to negotiate from a position of information rather than reacting to a number the buyer’s side has already set.
Why This Matters More in San Francisco Than in Newer Markets
Reporting from the San Francisco Chronicle notes that more than 40 percent of San Francisco’s homes were built before 1940, a share driven by the city’s early Gold Rush-era growth and decades of comparatively slow development since. That concentration of pre-war housing means knob and tube wiring is not a rare find here the way it might be in a newer suburb. It is a routine part of buying or selling in neighborhoods like Noe Valley, the Richmond, or the Mission, and both buyers and sellers benefit from treating it as an expected part of the process rather than a red flag unique to one property.
San Francisco’s mix of single-family homes and multi-unit buildings adds another wrinkle for buyers specifically. If you are purchasing a unit in a duplex or small apartment building, the knob and tube wiring may not be confined to your unit alone. It is worth asking whether the building’s wiring has been evaluated as a whole, since resolving an insurance or inspection issue in a shared building sometimes requires coordination with other owners or a homeowners association, not just work inside your own walls.
Condos, TICs, and Shared Buildings Add Their Own Complications
Tenancy-in-common properties and small condo buildings are common in San Francisco, and they change how a knob and tube wiring issue gets resolved. In a single-family home, one owner makes every decision about inspection timing, contractor selection, and payment. In a shared building, the electrical system serving multiple units may fall under a mix of individual ownership and shared responsibility, depending on how the building’s governing documents define it. Before assuming a wiring issue is purely a personal expense, it is worth checking whether the building’s HOA or co-ownership agreement addresses shared electrical infrastructure, since that can change who pays for what and how quickly a fix can actually happen. A buyer evaluating a TIC or small condo with knob and tube wiring should ask these questions before closing, not after moving in and discovering the building’s decision-making process is slower than expected.
What an Inspection Report Should Cover
A useful electrical inspection for a real estate transaction should answer a few specific questions: is the knob and tube wiring still carrying power, where does it run, is it isolated to certain rooms or spread throughout the home, and what would a partial versus a full rewire realistically cost. It is also worth having the electrician note any related issues found along the way, since homes from this era often carry a handful of other electrical quirks alongside knob and tube wiring, things like ungrounded two-prong outlets, older fuse-based panels, or circuits that were extended without a corresponding panel upgrade. Documenting all of it in one report gives both sides of a transaction a complete, shared picture instead of piecemeal findings that surface one at a time.
This kind of report also becomes useful well beyond the transaction itself. A new owner who keeps a documented electrical inspection on file has something concrete to hand their own insurance carrier at the next renewal, and something to reference if they decide to complete a rewire in phases rather than all at once. Treating the inspection as a durable record, not a one-time hurdle to clear before closing, tends to save time on every electrical conversation that follows.
Turning a Disclosure Requirement Into a Smoother Transaction
The new disclosure law was written to protect buyers, but it can just as easily protect sellers who use it as a prompt to get organized early. A documented, professional inspection turns a vague disclosure sentence into a concrete answer, and a concrete answer is almost always easier to negotiate around than an unknown. Whether you are weeks away from listing a San Francisco home or actively touring older properties, getting a licensed electrician’s eyes on the wiring before it becomes a deadline-driven scramble is the difference between a manageable line item and a last-minute crisis.
None of this needs to feel like a reason to avoid San Francisco’s older housing stock altogether. The city’s Victorians, Edwardians, and prewar cottages are part of what makes its neighborhoods distinctive, and knob and tube wiring is simply part of the maintenance history that comes with a home of that age, the same way an older roof or original plumbing might be. The goal is not to eliminate every older home from consideration. It is to make sure the wiring gets the same clear-eyed evaluation as any other major system before a purchase or sale is finalized, so nobody is working from a disclosure form’s general language alone when real money and real decisions are on the line.
If you are preparing to buy or sell an older home anywhere in San Francisco, our team offers a full electrical troubleshooting and safety inspection that documents exactly what a lender, an insurer, or a buyer’s agent is likely to ask about. You can see the rest of the electrical services we provide across the city on our San Francisco electrician services page.
