# Will electricians work on knob and tube wiring?

> Will electricians work on knob and tube? What they take on and turn down, why small jobs get declined, and how to check a C-10 license and SF registration.

URL: https://fogcitysfknobandtube.com/guide/will-electricians-work-on-knob-and-tube/

**In short**

What electricians will and will not do with old wiring, the friction homeowners report when hiring, and how to check that a contractor can legally do the work in San Francisco.

**Last updated**

October 30, 2026

Yes. Testing, replacing, disconnecting and certifying knob and tube are ordinary electrical work. What some will not do is extend it, add new outlets to an old circuit or take on a small job in a knob and tube house without dealing with the old wiring. The friction homeowners report is less about refusal than about availability, scope and comparable bids.

[Fog City SF Knob and Tube](https://fogcitysfknobandtube.com/) manages knob and tube replacement in San Francisco and the East Bay: the company takes the job from the first walk-through to the final inspection, and the electrical work is carried out by licensed and insured California C-10 electrical contractors. This guide explains what electricians typically take on and decline, why, and how to check that whoever you hire can legally do the work.

Key takeaways

- Replacement, testing, disconnection and certification are ordinary electrical work; extending knob and tube is what many decline
- Homeowners report trouble getting small jobs taken, long lead times and quotes that leave plaster patching out
- Check a contractor's CSLB license for the C-10 classification and workers' compensation
- Workers doing electrical work for a C-10 contractor must hold state electrician certification
- To file San Francisco permits, a contractor registers with DBI and supplies an SF Business Registration Certificate

## What electricians will and will not do

The answer depends on the job, not on the wiring.

| Job | Usually taken on? | Why |
| --- | --- | --- |
| Testing and mapping circuits | Yes | It is the first step for any decision about old wiring; the [knob and tube inspection](https://fogcitysfknobandtube.com/knob-and-tube-inspection/) covers it |
| Whole-house replacement | Yes | Ordinary rewiring work, though plaster access shapes who bids |
| Replacing remaining circuits | Yes | A defined scope with a clear end point |
| Disconnecting abandoned runs | Yes | Required for unused conductors, which must be removed or identified and terminated; see [knob and tube removal](https://fogcitysfknobandtube.com/knob-and-tube-removal/) |
| Certifying knob and tube for insulation | Yes, by a licensed electrical contractor | California’s insulation exception requires that survey and certification, as the [attic insulation service](https://fogcitysfknobandtube.com/knob-and-tube-attic-insulation/) explains |
| Certifying knob and tube as inactive for BayREN | Yes, by a licensed electrician | The rebate needs the certification and invoice |
| Repairing one damaged splice or device | Sometimes | Depends on condition; some prefer to replace the run |
| Extending or tapping a knob and tube circuit | Often declined | Splicing onto old conductors is where many problems start |
| A small new circuit in a knob and tube house | Sometimes declined | Homeowners report some firms only take larger projects |

### Why extending old circuits is declined

The “no” that matters most is to adding onto an existing knob and tube circuit, and it is a sound one. Extending a circuit means splicing new conductors onto old ones whose rubber insulation may crack when moved, on a circuit that has no ground and may already be overloaded. The City of Alameda’s Building Official states plainly that knob and tube “cannot be extended,” while allowing existing wiring to be repaired or re-energized. The alternative is a new circuit from the panel, run in grounded cable, which is how new loads should arrive in an old house anyway. The [repair or replace guide](https://fogcitysfknobandtube.com/guide/can-knob-and-tube-wiring-be-repaired/) covers when a repair is still reasonable.

## What homeowners report when hiring

Homeowners’ own accounts describe a handful of recurring frictions. They are reports, not measured rates, and willing contractors clearly exist: homeowners also describe completed [whole-house rewires](https://fogcitysfknobandtube.com/whole-house-rewiring/) of knob and tube houses around the Bay Area.

- **Small jobs turned away.** Homeowners report that when they asked for one new circuit in a knob and tube house, most electricians they called said they only take large projects.
- **Lead times.** Homeowners report that electricians who do this work are busy and can take a while to respond, and some San Francisco owners facing an [insurer’s deadline](https://fogcitysfknobandtube.com/guide/knob-and-tube-insurance-california/) describe it as a shortage.
- **Patching left out.** Homeowners report quotes where one electrician would cut the openings but not restore lath and plaster, while another priced the repair as a separate line. The gap is the patching, not the electrical work.
- **Being steered away from replacement.** Some homeowners report electricians advising that undisturbed knob and tube in good condition did not need replacing, which can be a reasonable judgment for a few sound circuits and no insurer or sale pressing.
- **Bids that do not match.** Homeowners report wide spreads between bids for similar houses, including one priced per square foot without the bidder entering the attic, in a house that had already been partly rewired.
- **Permit worries.** Some owners report delaying a rewire because they fear an inspector will raise unrelated unpermitted work.

Most of these come back to scope. An electrician who does not want to restore plaster, or to take on a job that will grow once the walls are open, may decline or price defensively. A written scope that lists each circuit and opening, and says who closes each one, gives every bidder the same job to price. The [rewiring quote checklist](https://fogcitysfknobandtube.com/guide/rewiring-quote-checklist/) lists the lines to ask for, and the [plaster-wall rewiring](https://fogcitysfknobandtube.com/plaster-wall-rewiring/) service explains how openings are planned in older walls.

## Who can legally do the work in San Francisco

### The state license

In California, contractor licensing is handled by the Contractors State License Board. The C-10 electrical contractor classification covers placing, installing and connecting electrical wires and equipment. DBI lists the classifications it accepts for electrical permits: B, C-7, C-10, C-45, C-46, C-61 or D-34, with C-10 covering any electrical work and a B general contractor accepted only after approval based on the scope.

### Certification for the people doing the work

Under California Labor Code section 108, people performing work as electricians for a C-10 contractor must be certified by the Division of Labor Standards Enforcement. A sole-owner C-10 licensee working alone does not need separate certification, and electricians coming from out of state must certify before working in California, with no grace period.

### San Francisco registration

San Francisco adds city-side steps for the firm rather than a separate city license. To file no-plan electrical permits online, a contractor registers with DBI, authorizes its CSLB license on PermitSF and supplies a valid San Francisco Business Registration Certificate and proof of workers’ compensation. The San Francisco Electrical Code issues permits to licensed contractors registered with DBI’s Central Permit Bureau, or to a qualifying homeowner. In Oakland, permits go to a California-licensed contractor with an appropriate classification and a current Oakland Business Tax Certificate, or to the owner.

### The homeowner route

San Francisco limits the homeowner electrical permit to owners of stand-alone single-family homes that are their primary residence, who must do the work themselves; LLCs are not eligible, and the Permit Center may tell an owner to hire a licensed contractor. Owners of flats, condos and TIC units cannot use it. The [can I replace knob and tube myself guide](https://fogcitysfknobandtube.com/guide/can-i-replace-knob-and-tube-myself/) covers that route honestly, and the [San Francisco electrical permit guide](https://fogcitysfknobandtube.com/guide/san-francisco-electrical-permit/) covers the permit and inspections for everyone else.

## How to check a contractor before you hire

1. **Look up the license.** Use the CSLB license lookup with the license number on the quote. Confirm it is active and carries the classification that fits the work.
2. **Check workers’ compensation, bond and insurance.** The CSLB license record lists the contractor’s bond and its workers’ compensation policy with effective and expiration dates, and shows a suspension if coverage lapsed. CSLB notes its database can lag, so ask for current certificates, including general liability, as well.
3. **Ask who does the wiring.** If employees do the work, they should hold state electrician certification.
4. **Confirm the permit.** Ask which DBI permits the quote includes and who will pull them. Work without a permit costs nine times the issuance fee plus the original fee in an investigation charge, and concealed work can be ordered opened.
5. **Ask about the test.** A contractor who quotes after testing circuits and looking in the attic and basement is pricing your house rather than an average.
6. **Read the patching line.** Ask who closes each opening and to what finish.

## How the work is arranged here

Fog City SF Knob and Tube manages each job and the electrical work is carried out by licensed and insured C-10 electrical contractors. Every circuit is tested at the walk-through, the written scope and price lists each opening and who closes it, plaster patching is included as an itemized line, and the job ends with a written circuit record and a labeled panel directory. For BayREN’s knob and tube rebate, the contractors supply the licensed electrician’s invoice or inactivity certification the program needs, and the company helps with the rebate paperwork; the [BayREN rebate guide](https://fogcitysfknobandtube.com/guide/knob-and-tube-rebate-bayren/) covers the conditions, and approval rests with BayREN.

If you are looking for someone to take on your house, call (628) 296-7628 or [request an estimate](https://fogcitysfknobandtube.com/contact/) with the age of the house, the number of units and what prompted the question. The [cost guide](https://fogcitysfknobandtube.com/guide/knob-and-tube-replacement-cost-san-francisco/) gives typical ranges in the meantime.

**Questions**

## Questions about this guide

### How do I check an electrician's license in California?

Use the Contractors State License Board's license lookup with the contractor's license number or business name. Check that the license is active, that it carries the C-10 electrical classification or another one that fits the work, and that the record lists a current workers' compensation policy. The people doing the wiring for a C-10 contractor must also hold state electrician certification.

### Why do some electricians turn down small jobs in knob and tube houses?

Homeowners report it most with one-circuit requests, such as a new line for an induction range. A small job in an old house can grow once the electrician finds the panel is full or the only nearby circuit is knob and tube, which many will not extend. Asking for the new circuit to run from the panel, with the panel checked first, makes the job easier to quote.

### Does San Francisco require a city electrician license?

No separate city electrician license was found. Licensing is state-level: a CSLB contractor license, such as C-10, and state electrician certification for workers. To file permits in San Francisco, a contractor registers with DBI, authorizes its license on PermitSF and supplies a San Francisco Business Registration Certificate and proof of workers' compensation.

**Read next**

## More guides

- [Decision GuideWhat should a rewiring quote include?The lines that make two knob and tube rewiring quotes comparable, what each one tells you, and the gaps that turn into surprises later.](https://fogcitysfknobandtube.com/guide/rewiring-quote-checklist/)
- [Decision GuideCan I replace knob and tube myself?Who San Francisco lets do their own electrical work, what the homeowner permit commits you to, why this site gives no wiring instructions, and the useful parts of the job an owner can take on.](https://fogcitysfknobandtube.com/guide/can-i-replace-knob-and-tube-myself/)
- [LearnHow does a San Francisco electrical permit work for rewiring?Who can file, what DBI charges, what each inspection checks, and why a Green Tag on its own does not prove the knob and tube is gone.](https://fogcitysfknobandtube.com/guide/san-francisco-electrical-permit/)
- [Decision GuideCan knob and tube wiring be repaired?Where a repair is honest and permitted, where it turns into an extension or a replacement, and how insurers and the insulation rules change the math.](https://fogcitysfknobandtube.com/guide/can-knob-and-tube-wiring-be-repaired/)
- [Cost GuideHow much does knob and tube replacement cost in San Francisco?The ranges, what moves a house within them, and the parts of the price that come from public figures.](https://fogcitysfknobandtube.com/guide/knob-and-tube-replacement-cost-san-francisco/)