# Partial Knob and Tube Replacement in Los Angeles

> Partial knob and tube replacement in Los Angeles: which circuits to replace first, how the remaining boundary is documented, and what insurers and buyers ask for.

URL: https://laknobandtube.com/partial-knob-and-tube-replacement/

Replace the live circuits that matter now and document exactly where the old system stops.

Questions answered

Last Updated: October 25, 2026

**19.1%** of homes in the City of LA were built before 1940, by the Census Bureau's count

**Express** LADBS issues nearly every house rewire permit as an express permit, with no plan check

**394.12** California's rule on insulating over knob and tube, explained in plain terms

[LA Knob and Tube](https://laknobandtube.com/) handles partial knob and tube replacement across Los Angeles: replacing the old circuits that matter most now, disconnecting them properly, and writing down exactly which ones remain. Partial jobs come up in pre-war houses that have already been through a remodel or two. A kitchen redone in the 1980s, a bathroom added in the 2000s and a panel swapped along the way can leave a house where half the outlets run on modern cable and the other half still run on porcelain knobs in the attic.

That mix is the reason a partial job has to start with a map. The visible outlets do not tell you which circuit feeds them, and a three-prong outlet can sit on a knob and tube run. A replacement planned room by room, without knowing where each circuit actually goes, can leave old wiring live in places nobody expected.

## What happens on the first visit

The first visit sorts the house into live, dead and mixed wiring. The panel shows which circuits exist and how they are protected. The attic and crawlspace show where the original runs go, whether they still connect to anything, and where later wiring was spliced into them. Outlets and lights are then matched to their circuits, so the map shows which rooms depend on knob and tube today.

The visit also looks at access. Where a pre-1940 house sits on a raised wood floor over a crawlspace, with an open attic above, those two spaces decide how much plaster has to be opened. The guide to [active and abandoned knob and tube](https://laknobandtube.com/guide/active-vs-abandoned-knob-and-tube/) explains how the difference between a live run and a dead one is confirmed without anyone touching the wiring by hand.

## Why the boundary matters more than the size of the job

A partial replacement leaves two systems in one house, so the useful question is where one stops and the other begins. Every circuit in scope is disconnected at both ends, at the panel and at the last device, so the old run cannot be energized again by accident. Abandoned runs can stay in place or be removed, and the [knob and tube removal](https://laknobandtube.com/knob-and-tube-removal/) page covers when pulling them out is worth the extra access.

The circuits that stay are listed by name, with the rooms and outlets they serve. That list is what an insurer, a buyer’s inspector or a future electrician needs. Without it, the house is easily described as rewired when it is not, which is the misunderstanding most likely to cause trouble later, at a sale or after a claim.

LADBS permit records show how ordinary this kind of job is. Descriptions filed in the City of LA include a partial rewire to remove knob and tube in parts of a house in Los Feliz and a 200-amp service upgrade with sections of knob and tube rewired in Echo Park. Both describe a house that will keep some original wiring after the work.

## Choosing which circuits to replace first

The order usually follows load and condition. Kitchen and bathroom outlets carry the heaviest appliances and sit closest to water, so they tend to go first, and replacing them brings GFCI protection where the code calls for it. Circuits with later splices, especially ones added without a junction box, come next, because a splice made decades after the original installation is often a weaker point than the original porcelain.

Attic runs matter if insulation is planned. California’s electrical code allows insulation over knob and tube only after a California-licensed electrical contractor surveys and certifies the wiring, so the other route is to replace the attic circuits first and insulate without conditions. The [attic insulation page](https://laknobandtube.com/knob-and-tube-attic-insulation/) covers both paths. Circuits feeding space heaters, window air conditioners or a home office are also early candidates, since original circuits were laid out for a few lights and outlets per room.

Replaced circuits in living areas get arc-fault protection under the California Electrical Code, either at the breaker or at the first outlet. The guide to [AFCI and GFCI on old wiring](https://laknobandtube.com/guide/afci-gfci-knob-and-tube/) explains what each device does and what it cannot do for the circuits that stay.

## Partial replacement and insurance

Insurance is often what decides between partial and full. Some carriers decline a house with any active knob and tube, while others accept partial work with an electrician’s letter describing what remains. That varies by carrier and changes over time, so ask your carrier or broker for its requirement in writing before the scope is set. A partial job that leaves the one circuit the insurer cares about does not solve the problem it was meant to solve. The [California insurance guide](https://laknobandtube.com/guide/knob-and-tube-insurance-california/) covers what to ask and what paperwork usually helps.

## Access, openings and patching

A partial job usually opens fewer walls than a full one, because it touches fewer rooms. New cable for first-floor outlets usually comes up from the crawlspace through the floor plate, and ceiling lights and upstairs circuits come down from the attic. Openings are needed where a route has to cross a fire block, a header or a wall with no open space above or below it, and at boxes that have to be replaced.

Pre-war houses were typically finished in plaster on wood lath, which patches differently from drywall. The quote should name each planned opening and say whether patching, texture and paint are included. The [plaster wall rewiring](https://laknobandtube.com/plaster-wall-rewiring/) page explains how routes are chosen to keep openings small.

## Permits and inspection

Replacing circuits is permitted work. In the City of Los Angeles, LADBS issues the electrical permit, and records show nearly every house rewire permit is issued as an express permit without plan check. An inspector checks the new wiring before walls are closed and again at the end. Pasadena, Glendale and South Pasadena permit through their own building departments. The [Los Angeles rewiring permit guide](https://laknobandtube.com/guide/los-angeles-rewiring-permit/) covers who can pull the permit and what the inspections look at.

## What a partial job costs

Partial jobs vary too much for a single published range. The price depends on the number of circuits in scope, how open the attic and crawlspace are, how many boxes need replacing and how much patching is included. The [LA cost guide](https://laknobandtube.com/guide/knob-and-tube-replacement-cost-los-angeles/) explains each of those factors, and the [cost estimator](https://laknobandtube.com/tools/knob-and-tube-cost-estimator/) shows how they move a whole-house figure.

## When full replacement makes more sense

A partial job stops making sense when most of the house still runs on original wiring, when the insurer will only accept a house with none left, or when the remaining circuits share neutrals or splices with the ones being replaced. At that point the [whole-house rewiring](https://laknobandtube.com/whole-house-rewiring/) page is the better starting place, and the same circuit map carries over.

## What's included

- A walk-through that identifies which outlets and lights are still fed by knob and tube
- A circuit map separating live, abandoned and mixed runs
- New cable for the circuits in scope, run through the attic and crawlspace where possible
- New boxes and devices where old ones are not safe to reuse
- Disconnection of the replaced knob and tube runs at both ends
- Panel connections, labeling and the city permit and inspection
- A written list of every circuit that still runs on knob and tube
- A stated plan for openings and who closes them

## Partial or full replacement

|  | Partial replacement | Full replacement |
| --- | --- | --- |
| Best fit | A house where remodels already replaced some circuits, or where one area matters now | A house where most lights and outlets still run on original wiring |
| What is left | Named circuits that still run on knob and tube | No live knob and tube |
| Insurance | Accepted by some carriers and not others; ask before scoping | The scope most likely to satisfy an insurer |
| Openings | Limited to the rooms in scope | At boxes throughout and where routes cross framing |
| Later work | A second phase can follow the same circuit map | None for branch wiring |

## Related resources

- Decision Guide [Is knob and tube still active in your house, or abandoned?](https://laknobandtube.com/guide/active-vs-abandoned-knob-and-tube/)How live, dead and mixed wiring is told apart, why the answer is rarely visible, and what it changes for an insurer, an insulation job and removal.
- Learn [How does knob and tube affect home insurance in California?](https://laknobandtube.com/guide/knob-and-tube-insurance-california/)What carriers tend to ask, how to get their answer in writing, what an electrician's letter can and cannot say, and where the FAIR Plan fits.
- Cost Guide [How much does knob and tube replacement cost in Los Angeles?](https://laknobandtube.com/guide/knob-and-tube-replacement-cost-los-angeles/)The ranges, what moves a house within them, and the parts of the price that come from public figures.
- Learn [Do AFCI and GFCI protection work on knob and tube wiring?](https://laknobandtube.com/guide/afci-gfci-knob-and-tube/)What each device senses, when the code requires them, and why they reduce some risks on old circuits without replacing the wiring.
- Learn [How do you identify knob and tube wiring?](https://laknobandtube.com/guide/how-to-identify-knob-and-tube/)A look-only guide to the clues in attics, crawlspaces, fuse boxes and rooms, and why what you can see is never the whole answer.

## How a job runs

1. First call What you have seen, the age of the house, and any inspection, insurer or escrow deadline.
2. Walk-through and circuit map Which runs are live, which are dead, the panel, attic and crawlspace access, and where openings would go.
3. Permit and rewire Circuits are replaced in sequence, so most of the house keeps power on most days.
4. Inspection and patching The city inspection, a labeled panel, and the openings closed as the quote describes.

## What this work looks like

A removed porcelain knob and porcelain tube resting on an attic joist beside an old nail

A gloved hand holding a non-contact voltage tester near an old outlet on a plaster wall

A dining room in a 1920s LA house with a built-in china cabinet, drop cloths and a stepladder during rewiring

A new white outlet set in the original white tile backsplash of a 1920s Los Angeles kitchen

Before

After

## Partial replacement questions

### Is partial knob and tube replacement safe?

It can be, when the circuits that stay are in sound condition, protected by correctly sized fuses or breakers, and not buried in insulation. The circuits that stay keep their original limits, so a partial job is a decision about priorities, not a fix for the whole house.

### Which circuits should be replaced first?

Usually the ones carrying the most load or showing the most wear: kitchen and bathroom outlets, circuits with later splices, runs in attic areas due for insulation, and anything feeding space heaters or window air conditioners.

### Will my insurer accept a partial replacement?

Some carriers do and some only accept a house with no live knob and tube. Ask the carrier or broker before the work is scoped, and keep the written list of remaining circuits for them.

### Can the rest be replaced later?

Yes. A partial job built on a full circuit map lets a second phase pick up where the first stopped, using the same routes and panel space.

### Does partial replacement need a permit in Los Angeles?

Yes. Replacing circuits is permitted electrical work. In the City of LA that is an LADBS electrical permit; Pasadena, Glendale and South Pasadena issue their own.

## Related services

### Inspection

Find out which circuits are still live, what condition the reachable wiring is in, and what cannot be seen.

### Whole-house rewiring

Replace every old branch circuit, knob and tube or not, and add the circuits and protection a modern house needs.

### Removal

Disconnect old runs for good, prove they are dead, and pull out the ones that are worth removing.