# Replacing knob and tube during a San Francisco remodel

> Knob and tube found in a kitchen, bath or garage remodel: how far past the work zone to replace, sequencing with DBI's pre-cover inspection, and costs.

URL: https://fogcitysfknobandtube.com/remodel-knob-and-tube-replacement/

**Service**

Old wiring replaced while a kitchen, bath or garage is open, with each circuit followed past the work zone so nothing new is spliced onto old runs.

Last Updated: October 30, 2026

**Where**

San Francisco and the East Bay: Berkeley, Oakland, Alameda and Piedmont.

**Local rules**

- An electrical permit from DBI before new wiring goes in, then a pre-cover and a final inspection.San Francisco Electrical Code 89.127
- A separate permit for each dwelling unit, except in single-family (R-3) buildings.DBI fee schedule
- Only owner-occupants of a single-family home may pull their own electrical permit.SF Department of Building Inspection
- No insulation around concealed knob and tube without a licensed electrical contractor's certification.California Electrical Code 394.12
- Up to $2,000 toward active knob and tube for income-qualified PG&E customers in an EASE Home project.BayREN

[Fog City SF Knob and Tube](https://fogcitysfknobandtube.com/) replaces knob and tube wiring during kitchen, bathroom, garage and other remodels in San Francisco and the East Bay. The company tests the circuits in and around the work, sets the boundary of the replacement and schedules it with the general contractor and DBI’s inspections; the electrical work is carried out by licensed and insured electrical contractors.

A remodel is one of the ways old wiring turns up, and one of the best times to replace it. DBI’s electrical permit records show it: of the permits filed since January 2016 that mention knob and tube, 156 also mention a remodel or renovation. When the walls are already open, new cable can be run without fishing and without extra openings, and the old runs can be pulled out instead of left in the cavity. The decision a remodel forces is not whether to replace the wiring in the room but how far past the room to go.

## What happens on the first visit

The first visit tests every circuit that enters, crosses or is fed from the remodel zone, and follows each one to see what else it serves. A kitchen circuit in an older San Francisco house can also feed a dining room, a hall light or the bedroom above. At the panel or fuse box, the visit records what protects each circuit and how much room there is for the new ones a remodel needs.

Ideally this happens before demolition, when the plan can still change. If the walls are already open, the exposed runs show where the eras meet, but nothing is cut or moved until testing shows what is live; the [active vs abandoned guide](https://fogcitysfknobandtube.com/guide/active-vs-abandoned-knob-and-tube/) explains why. The result is a written scope and price that draws the boundary: which circuits are replaced, which old circuits remain in service elsewhere, where each one ends, and every opening outside the remodel zone and who closes it.

## How far past the remodel to go

Wiring is organized by circuit, not by room, and that is what makes the boundary a real decision. Replacing only the wiring inside the opened walls is the smallest scope, and it fits when the room’s circuits serve nothing else. When an old circuit runs through the kitchen and on to other rooms, replacing it inside the kitchen and reconnecting it outside leaves a splice between eras in a wall that is about to close.

The middle option replaces every old circuit that touches the zone, all the way to its last outlet. It usually needs a few openings beyond the remodel, but it leaves no hybrid circuit behind. The largest option treats the remodel as the start of a [whole-house rewire](https://fogcitysfknobandtube.com/whole-house-rewiring/), using the open walls as the main route for a floor. Homeowners report weighing exactly this question once demolition shows how much original wiring is left, sometimes when finishing the job would mean taking down a ceiling that was meant to stay. A test of every circuit puts a scope and a price on each option before that choice is made. Where only a few old circuits remain after the remodel, [partial knob and tube replacement](https://fogcitysfknobandtube.com/partial-knob-and-tube-replacement/) covers them, with a written record of what is left.

## When demolition exposes knob and tube

Remodels open walls nobody has looked into for decades, and what is inside may be knob and tube. The rule on site is simple: work stops in that area and the wiring is left alone until it is tested. Runs that look abandoned can be live, and the rubber insulation on old conductors cracks when it is pulled, bent or stepped on. Testing shows what each run feeds, and the boundary is drawn from there.

The other common find is a hybrid: cloth-insulated or modern cable connected to knob and tube at a splice somewhere in the ceiling. Some earlier remodels did exactly what this one should avoid, running new cable to the nearest old circuit. The [guide to knob and tube mixed with Romex](https://fogcitysfknobandtube.com/guide/knob-and-tube-mixed-with-romex/) explains how those joints form, and [cloth wiring replacement](https://fogcitysfknobandtube.com/cloth-wiring-replacement/) covers the cable that followed knob and tube.

## Why new work is not spliced onto old

Every new circuit for the remodel runs back to the panel as a home run. Connecting it to an existing knob and tube circuit would put an ungrounded, aging section of wiring behind new outlets, inside a wall that is about to be closed, on a circuit protected for the older conductors. No San Francisco amendment addresses extending knob and tube, and the city’s code lets existing wiring remain if it was legal when installed and maintained; the plan avoids the question by not extending it. In the East Bay, the City of Alameda’s Building Official states plainly that knob and tube cannot be extended.

New and changed circuits are built to the California Electrical Code San Francisco adopted, operative January 1, 2026. Branch circuits that are modified, replaced or extended in most living areas need arc-fault protection, kitchens, bathrooms, laundry areas and the other listed locations need ground-fault protection, and new receptacles must be tamper-resistant. The [AFCI and GFCI guide](https://fogcitysfknobandtube.com/guide/afci-gfci-knob-and-tube/) covers each device. Where the remodel adds an induction range, a heat pump dryer or other heavy loads, a load calculation shows whether the panel can carry them, and an [electrical panel upgrade](https://fogcitysfknobandtube.com/electrical-panel-upgrade/) is planned into the same project if it cannot. Piedmont goes further than the state code in the East Bay: its local amendments require at least one 240-volt, 50-amp circuit within 6 feet of the kitchen cooking appliance location, and apply that rule when circuits near an existing or proposed range or oven are modified, or when more than half of a unit’s 120/240-volt wiring is replaced.

## Sequencing with the general contractor and DBI

The electrical work has to fit between demolition and wallboard. San Francisco requires a DBI electrical permit before new wiring or alterations begin; licensed contractors in the classifications DBI lists may apply, with the C-10 electrical license covering any electrical work. The work then gets a pre-cover inspection before any wiring is covered or concealed, and DBI can order concealed, uninspected work exposed at the owner’s expense. So the sequence is fixed: rough-in, pre-cover inspection, then insulation and wallboard, then devices, final inspection and the Green Tag. The [San Francisco electrical permit guide](https://fogcitysfknobandtube.com/guide/san-francisco-electrical-permit/) walks through each step.

Insulation is the other reason to settle the wiring first. The California Electrical Code bars concealed knob and tube in insulated hollow spaces of walls, ceilings and attics where the insulation envelops the conductors, except under a narrow certification process. A remodel that insulates exterior walls or the ceiling below an attic has to deal with any knob and tube left in those cavities; [knob and tube under attic insulation](https://fogcitysfknobandtube.com/knob-and-tube-attic-insulation/) explains the options. DBI also presumes buildings built before 1979 contain lead paint unless a certified inspector shows otherwise, which shapes how plaster outside the remodel zone is opened; the [lead and asbestos guide](https://fogcitysfknobandtube.com/guide/lead-and-asbestos-during-rewiring/) explains what that adds.

## What it costs

The wiring inside the remodel zone is priced as part of the remodel’s electrical scope, and open walls make it the cheapest wiring in the house to replace. Going further is priced by circuits and access. For several remaining circuits, a national budgeting range is $2,000 to $10,000; for a whole-house knob and tube replacement in a San Francisco single-family home, a typical range for the electrical scope is $20,000 to $50,000 or more, with permits. Current DBI electrical permit fees run from $305 for up to 10 outlets or devices to $740 for more than 40. Openings outside the remodel zone are patched as an itemized line in the quote. The [San Francisco cost guide](https://fogcitysfknobandtube.com/guide/knob-and-tube-replacement-cost-san-francisco/) explains what moves each number.

**Scope**

## What's included

- A test of every circuit that enters, crosses or is fed from the remodel zone, recording what else each one serves
- A boundary written into the scope: which circuits are replaced, which old ones stay in service elsewhere, and where they end
- New circuits for the remodel run back to the panel as home runs
- A load calculation for new kitchen, laundry or appliance circuits, and panel work planned in when it is needed
- Old runs in the open walls disconnected at both ends and removed while they are reachable
- Scheduling with the general contractor so rough-in and the pre-cover inspection land before insulation and wallboard
- DBI permit, pre-cover and final inspections, a written circuit record and a labeled panel directory
- Patching of openings outside the remodel zone, itemized in the quote

**Choosing the scope**

## How far past the remodel to replace knob and tube

| Compare | Remodel zone only | Every circuit that touches the zone | The whole floor or house |
| --- | --- | --- | --- |
| What is replaced | Wiring inside the opened walls; new home runs for the room | Each old circuit that passes through or feeds the zone, to its end | Every old branch circuit |
| Old wiring left live | Circuits beyond the zone, documented | Only circuits that never touch the zone | None |
| Openings outside the remodel | None | A few, where those circuits run on | Planned on every floor |
| Best fit | The room's circuits do not serve anything else | Kitchen or bath circuits also feed nearby rooms | Most of the house is original and the budget allows |
| Typical cost | Priced within the remodel's electrical scope | $2,000 to $10,000 for several circuits, a national budgeting range | $20,000 to $50,000 or more, a typical San Francisco range |

**Read next**

## Related resources

- [LearnWhat does it mean when knob and tube is mixed with Romex?Most remodeled older houses have both systems. Where they meet, why those joints matter more than the old wire itself, and how a scope deals with them.](https://fogcitysfknobandtube.com/guide/knob-and-tube-mixed-with-romex/)
- [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/)
- [LearnHow can you tell active knob and tube wiring from abandoned runs?Live and dead knob and tube look identical. Insurers, the insulation rule, the BayREN rebate and the real hazard all turn on which one you have.](https://fogcitysfknobandtube.com/guide/active-vs-abandoned-knob-and-tube/)
- [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/)

**How a job runs**

## From the first call to the Green Tag.

### First call

Tell us what started this: an insurer's letter, an inspection report, a remodel, an attic you want to insulate.

The age of the house, the number of units and any deadline shape the next step.

### Walk-through

Circuits are tested to separate live knob and tube from abandoned runs, and attic, basement and garage access is checked.

Plaster, trim and finishes are noted, and you get a written scope and price.

### The work

The permit is filed with DBI. New cable is fished along the planned routes and openings are kept small.

The pre-cover inspection happens before anything is closed.

### Patching, inspection and the Green Tag

Once the pre-cover inspection passes, the openings are patched. Plaster patching is included and shown as its own line in the quote.

After the final inspection and the Green Tag, old runs are removed or terminated and the panel directory is updated.

**On the job**

## What this work looks like

New white cables run through open studs to blue electrical boxes in a bathroom under remodel

Two empty porcelain tubes still set in an old stud of an opened kitchen wall

Six new white cables stapled along a garage ceiling joist and turning up to the units above

New countertop receptacles in a kitchen under remodel, cabinets in place and the backsplash not yet tiled

**Questions**

## Remodel knob and tube replacement: questions

### Do I have to replace all the knob and tube when I remodel a kitchen?

Not by default. San Francisco's electrical code lets existing wiring stay if it was legal when installed and has been maintained. The new kitchen circuits are built to current code, and any old circuit that runs through the opened walls is the cheapest one in the house to replace. How far past the kitchen to go is a choice the testing informs.

### What should happen if demolition uncovers knob and tube?

Stop work in that area and leave the wiring alone until it is tested. Exposed runs can still be live even when they look abandoned, and old rubber insulation cracks when it is pulled or bent. Testing shows what each run feeds, which decides whether it is replaced, disconnected or left in service beyond the remodel.

### Can a remodeled kitchen's new outlets be fed from the knob and tube circuit next door?

Not well, and not in every city. The joint becomes the weakest point in the house: a splice between new cable and knob and tube leaves an ungrounded, aging circuit behind a new-looking outlet, inside a wall the remodel is about to close. New circuits run back to the panel as home runs instead. Alameda's Building Official states knob and tube cannot be extended at all.

### Does the knob and tube work need its own permit if the remodel already has one?

In San Francisco, new wiring or alterations need a DBI electrical permit before the work starts, filed by a licensed contractor in an eligible classification or, in limited cases, the homeowner, and the work is inspected before it is covered. Exactly how the electrical permit fits with the remodel's other permits is confirmed per project. Oakland folds house and duplex remodel electrical work into a combination permit.

### How much more does it cost to replace knob and tube beyond the remodel area?

It depends on how many circuits run on and how they can be reached. For several remaining circuits, a national budgeting range is $2,000 to $10,000. Extending the work while the remodel is open usually costs less than coming back later, because access, protection, permits and patching are not repeated.

**Related services**

## Other work on the same wiring

### Partial knob and tube replacement

The circuits still running on knob and tube replaced from the panel out, with a written record of exactly what remains.

### Whole-house rewiring

Every old branch circuit replaced, new circuits added where the house needs them, and the panel sized for the load.

### Electrical panel upgrade

A fuse box or undersized panel replaced, the service resized when the load calculation calls for it, and PG&E's side coordinated.