# Knob and Tube Inspection in Los Angeles

> Knob and tube inspection in Los Angeles for escrow and insurer letters: which circuits are live, what a home inspection misses. Book a circuit map walk-through.

URL: https://laknobandtube.com/knob-and-tube-inspection/

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

Questions answered

Last Updated: October 24, 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 knob and tube inspection across Los Angeles, Pasadena, Glendale and South Pasadena: mapping which circuits still run on the old wiring, checking the parts that can be reached, and writing down what cannot be seen. The work is carried out by licensed and insured electrical contractors. Most requests start with a piece of paper. A buyer’s home inspection report says knob and tube was observed in the attic. An insurer’s renewal letter asks whether any of it is still active. A seller wants to know what a buyer’s inspector is going to find.

Each of those asks a narrower question than “is there knob and tube?” They ask how much of it is live, what condition it is in, and what it would take to replace. That is what this inspection answers, as far as anyone can answer it without opening walls.

## What happens on the first visit

The visit starts at the panel. The number of circuits, the type of protection and the size of each fuse or breaker show how the house is fed and whether any circuit is protected at a size its wiring cannot carry. From there, outlets and lights are matched to circuits room by room, so the result is a map of which rooms depend on knob and tube today.

The attic and crawlspace come next. The accessible runs are followed by eye and with a light, looking for where porcelain knobs and tubes still carry conductors, where modern cable was spliced in, where insulation or stored boxes sit against the wiring, and where old runs end at nothing at all. None of this involves pulling on, cutting or handling the old conductors. The visit also records access for any later work: attic clearance, crawlspace height, wall finishes and where the routes would need to cross framing.

## What a general home inspection can and cannot tell you

A general home inspector looks at the whole house in a few hours, and the electrical part is a visual survey. When knob and tube is visible in the attic or crawlspace, the report usually notes it and recommends an electrician’s evaluation. That note is useful, but it rarely says how much of the system is live. Old runs are often left in place after a remodel, so the same porcelain can belong to a dead circuit or a live one, and the two look alike from a ladder.

The general report also cannot see wiring the inspector did not reach, and a three-prong outlet tells it nothing reliable about grounding. The [three-prong outlet guide](https://laknobandtube.com/guide/knob-and-tube-three-prong-outlets/) explains why a grounded-looking receptacle can sit on a two-wire circuit. A knob and tube inspection is a narrower, electrical look, and it does not replace the home inspection or carry a home inspector’s or engineer’s credential.

## Circuit tracing: from the panel to each room

Circuit tracing is how the map gets built. With a circuit tracer and testers, each fuse or breaker is matched to the outlets, switches and fixtures it feeds, and each of those is matched back to the wiring type that serves it. A kitchen may turn out to be fully modern while a bedroom on the same side of the house still runs on its original circuit. A circuit can also be mixed: modern cable from the panel to a box in the attic, then knob and tube from there to the rooms.

That mixed condition is common after remodels and is the one most likely to be misdescribed. The guide to [active and abandoned knob and tube](https://laknobandtube.com/guide/active-vs-abandoned-knob-and-tube/) covers how live, dead and mixed runs are told apart. The map is also the starting point for a [partial replacement](https://laknobandtube.com/partial-knob-and-tube-replacement/), because it shows exactly which circuits would remain.

## Condition: insulation, splices, boxes and protection

On the runs that can be seen, the condition questions are specific. Is the rubber and cloth insulation on the conductors intact where it passes over knobs and through tubes, or cracked and flaking? Has a later owner spliced new wire onto the old without a junction box, or tied modern cable into the middle of a run? Are junction boxes covered and secured? Is loose-fill or batt insulation lying over the conductors, which keeps them from shedding heat as they were designed to?

At the panel, the question is overcurrent protection. Original knob and tube circuits were designed around small fuses. A larger fuse or breaker than the wire can carry lets the wire overheat before anything trips. Fuse sizes are a matter for the electrician; never change one yourself. If you want to look for knob and tube before the visit, the [identification guide](https://laknobandtube.com/guide/how-to-identify-knob-and-tube/) explains what to look for from a safe distance, without touching anything.

## The limits of seeing concealed wiring

Most of a knob and tube circuit runs inside closed walls and ceilings. An inspection can confirm that a circuit is live, see the ends of it in the attic and crawlspace, and check its devices. It cannot see a splice made inside a wall cavity decades ago, a nail through a conductor, or insulation that has crumbled where no one can reach. A borescope can look into a cavity through an existing opening, but it does not see the whole run.

That is why no responsible report calls a house safe on the strength of visible wiring alone, and why the written summary lists what could not be verified. If the decision depends on something hidden, the next step is targeted access, decided with you, not a guess.

## Buyers in escrow and California’s electrical disclosure

In escrow, knob and tube usually surfaces in the buyer’s inspection report, and the buyer then has a contingency period to decide what to do about it. Since January 1, 2026, California sellers must also give buyers a written electrical statement under Civil Code section 1102.6i. It advises that a buyer may want a qualified professional to inspect the main panel, subpanels and wiring, and warns that substandard or faulty wiring can be a fire risk and can make property insurance harder to obtain.

For a buyer, the circuit map answers the cost question, since the number of live circuits drives the price of replacement. The insurance question runs alongside it. The [buyer’s guide](https://laknobandtube.com/guide/buying-a-house-with-knob-and-tube/) covers both, and sellers deciding whether to inspect before listing can start with the [seller’s guide](https://laknobandtube.com/guide/selling-a-house-with-knob-and-tube/).

## Insurer letters

Carriers differ. Some decline a house with any active knob and tube, some ask for an electrician’s letter stating whether it is active, and some accept a written replacement plan. No inspection can promise acceptance by a given carrier. What helps is asking the carrier or broker, in writing, exactly what the letter must say before the visit, so the summary answers that question in its own terms. The [California insurance guide](https://laknobandtube.com/guide/knob-and-tube-insurance-california/) lists the questions worth asking.

## Before insulating: the CEC 394.12 survey

California’s electrical code allows insulation where knob and tube is present only after an electrical contractor licensed by the State of California surveys the wiring and certifies that it is in good condition, with no deterioration, no improper overcurrent protection and no improper connections or splices. The certification is filed with the local building department and a copy goes to the owner. That survey is the licensed contractor’s signed statement, a separate step from a circuit map. No LADBS-specific form for it was found, so the filing is confirmed with the building department for the address. The [attic insulation page](https://laknobandtube.com/knob-and-tube-attic-insulation/) explains when certifying makes sense and when replacing the attic circuits is simpler.

## From inspection to a scope

The inspection does not decide the job; it shows which jobs are realistic. A single bad splice on an otherwise sound circuit points to a repair. A house where a remodel already replaced the kitchen and bath circuits points to a partial job. A house where most rooms still depend on original wiring, or an insurer that will accept none of it, points to [whole-house rewiring](https://laknobandtube.com/whole-house-rewiring/). Any repair, alteration or extension that follows is permitted work, inspected by LADBS in the City of LA or by the building department in Pasadena, Glendale or South Pasadena.

## What an inspection costs

There is no single published price for this work. What moves it is the size of the house, the number of circuits, how open the attic and crawlspace are, and whether a written letter for an insurer or a CEC 394.12 survey is part of the request. The [cost guide](https://laknobandtube.com/guide/knob-and-tube-replacement-cost-los-angeles/) covers what replacement costs once the map is done, and the [assessment tool](https://laknobandtube.com/tools/knob-and-tube-assessment/) helps you sort out how urgent your situation is before you call.

## What's included

- A review of the panel: how many circuits exist, how each is protected, and whether fuse or breaker sizes suit the wiring
- Outlets and lights matched to their circuits, room by room
- A look at accessible knob and tube runs in the attic and crawlspace, without disturbing them
- Notes on visible splices, later tie-ins and junction boxes
- A check of where insulation, storage or debris sits against old wiring
- Attic clearance, crawlspace height and wall finishes recorded for any later work
- A written summary of live, dead and mixed circuits, including what could not be seen

## General home inspection or knob and tube inspection

|  | General home inspection | Knob and tube inspection |
| --- | --- | --- |
| Purpose | A broad visual survey of the whole house | A focused look at the old wiring and how much of it is live |
| Knob and tube | Usually notes that it was seen | Maps which circuits still run on it |
| Live or dead | Often not determined | Circuits matched to outlets, lights and the panel |
| Splices and protection | Noted if obvious | Visible splices, tie-ins and fuse or breaker sizes reviewed against the wiring |
| Concealed wiring | Not seen | Not seen either; the limits are written down |
| Useful for | Deciding what to look into further | Choosing between repair, partial and full replacement, and answering insurer questions |

## Related resources

- Decision Guide [What should you know before buying a house with knob and tube?](https://laknobandtube.com/guide/buying-a-house-with-knob-and-tube/)How to fit an electrical evaluation, an insurance answer and a negotiation into the time escrow gives you.
- 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.
- 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.
- Decision Guide [What should you do when selling a house with knob and tube in California?](https://laknobandtube.com/guide/selling-a-house-with-knob-and-tube/)The disclosures every California seller gives, the choice between rewiring first and pricing it in, and the paperwork that keeps a partial job from becoming a surprise.

## 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

An old fuse box with four round plug fuses on a porch wall

A borescope camera cable entering a small hole beside a round ceiling box, its screen dark

A small wood crawlspace access door open in the river-rock foundation of a Los Angeles bungalow

A clipboard with a hand-drawn floor plan sketch and a circuit tracer on a dining table

## Inspection questions

### Can a knob and tube inspection tell me what is inside the walls?

Not directly. It can trace which circuits are live and check every part of the wiring that can be reached in the attic, crawlspace, panel and boxes. Splices and damage inside closed walls stay unknown until a wall is opened, and an honest report says so.

### Is a knob and tube inspection the same as a home inspection?

No. A general home inspection is a broad visual survey of the whole house and usually just notes that knob and tube was seen. A knob and tube inspection is an electrical look at that wiring: which circuits still use it, how they are protected and what condition the reachable parts are in.

### Will a knob and tube inspection satisfy my insurance company?

That depends on the carrier. Some want a letter on whether any knob and tube is still active, some want it replaced, and requirements change. Ask your carrier or broker in writing what the letter must say before the visit, so the report answers that question.

### How early in escrow should I book a knob and tube inspection?

As early in the inspection contingency as you can. The circuit map drives the cost of any replacement, and your insurer may need its own answer before closing, so leaving it to the last days narrows your options.

### What should I have ready for a knob and tube inspection?

The home inspection report if there is one, any letter from your insurer, and whatever you know about past remodels or a panel change. Clear access to the attic hatch, crawlspace entry and panel also helps the visit see more.

## Related services

### Partial replacement

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

### Whole-house rewiring

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

### Attic insulation

Certify the old wiring under California's exception, or replace the attic circuits first and insulate without conditions.