# How is knob and tube replaced?

> How is knob and tube replaced? Circuit mapping, the rewiring plan, new NM-B cable, devices, inspections and handover records. Follow each step in order.

URL: https://confluxcincinnatiknobandtube.com/guide/how-knob-and-tube-replacement-works/

Learn

What happens between our first visit and your final inspection, and why each step depends on the one before it.

Last Updated: November 11, 2026

The short answer

Knob and tube is replaced one circuit at a time. We trace and map every K&T circuit, plan new routes and circuits, and fish new grounded cable, usually NM-B, from the panel to new or reused boxes. IBI inspects the rough-in before walls close. Then devices go in, we disconnect old runs at both ends, and the final inspection follows.

Key takeaways

- The circuit map comes first, and we make every later decision from it.
- New cable runs from the panel to the last device on each circuit, so no K&T is left in the middle.
- Most routes use the attic, basement and closets. We plan openings in plaster; we don't cut at random.
- IBI inspects the rough-in before we close any opening.
- You finish with records: circuit map, panel directory, disconnection record and the permit final.

## What will actually happen in your house?

How is knob and tube replaced? We do it one circuit at a time, working from a map, while you keep living there. The order below is the same whether we’re replacing one circuit or the whole house; only the number of repeats changes.

This is how we run a job at [Conflux Cincinnati Knob and Tube](https://confluxcincinnatiknobandtube.com/), across Cincinnati, Hamilton County and Northern Kentucky, always under an electrical permit.

1. Inspection and circuit mapping
2. The rewiring plan
3. Permit
4. Protection and routes
5. Rough-in: new cable and boxes
6. Rough-in inspection
7. Devices, panel and testing
8. Disconnecting the old runs
9. Final inspection, patching and records

## What do we do on the first visit?

We turn your old wiring into a list. We trace every K&T circuit to its fuse or breaker and check each fuse size against the wire.

We follow the attic and basement runs and confirm each one live or dead at both ends. You get a written circuit map:

- **What each circuit feeds**, room by room
- **How many openings each room will need**
- **A status for every circuit**: replace now, replace later or dead

We don’t price or plan anything until that list exists.

## How do we turn the map into a plan?

The map shows what you have; the plan decides what replaces it. This is where we lay the house out for how you use the rooms now, not how someone wired them a century ago.

| Decision | What the map shows | What the plan sets |
| --- | --- | --- |
| Circuit count | A few long circuits serving several rooms each | More, shorter circuits; dedicated circuits for kitchen, bath and heavy appliances |
| Routes | Where old runs go and where access exists | Which walls we reach from the attic, which from the basement, which need an opening |
| Panel | Fuse sizes, panel space, service rating | Whether the panel or service changes, and when |
| Order | Which circuits matter most | Sequence, so one working circuit and your heat stay on |
| Scope boundary | Live, dead and mixed runs | What we replace now and what we record for later |

If we’re replacing only some circuits, the plan is a [partial replacement](https://confluxcincinnatiknobandtube.com/partial-knob-and-tube-replacement/) with a written boundary. If K&T runs through most rooms, it’s a [whole-house rewire](https://confluxcincinnatiknobandtube.com/whole-house-rewiring/).

## What kind of wire goes in?

Most house rewires use NM-B cable, sold under trade names such as Romex: two insulated wires and a bare ground inside one plastic sheath. That ground is the main thing K&T never had.

NM-B isn’t right everywhere. Some spots call for armored or metal-clad cable, for example where the cable could get damaged, and buildings of four or more units follow the Ohio Building Code, which can change the wiring method. Our plan names the cable for each run, and IBI inspects it.

## How does new cable get into plaster walls?

Mostly from above or below. From an open attic, we drop cable into a stud bay; from an unfinished basement, we bring it up. Closets, chases and stacked walls carry runs between floors.

One new cable showing at a small plaster opening beside a door casing, where the run had to get past the framing.

Where there’s no hidden path, we cut small openings at fire blocks, behind baseboards or at device locations, and list each one for patching. [Plaster-wall rewiring](https://confluxcincinnatiknobandtube.com/plaster-wall-rewiring/) explains how we keep openings few and patchable.

## What happens at rough-in, and when does IBI come?

Rough-in is when we run the new cable and set the boxes, before anything closes up. We shut off one circuit at a time, run new cable from the panel to every point on that circuit, and set or replace the boxes.

Then IBI inspects the rough-in. It won’t approve work it can’t see, so every opening stays open until the inspector passes it. Our [Cincinnati electrical permit](https://confluxcincinnatiknobandtube.com/guide/cincinnati-electrical-permit/) guide lists what the inspector checks.

## When do the new outlets and switches go in?

Once the rough-in passes. Every outlet on a replaced circuit becomes a grounded three-prong receptacle, we connect switches to the new wires, and we reconnect or replace fixtures.

- **Receptacles.** Grounded through the new cable’s ground, with GFCI where the code requires it, such as kitchens and baths.
- **Switches.** Wired to the new circuit. We keep period push-button switches only where a compatible mechanism goes in.
- **The panel.** Each new circuit lands on a breaker sized to its wire, with AFCI or GFCI breakers where required, and gets its own line in a labeled directory.

Then we test each circuit: continuity, polarity, a working ground at every receptacle, and protective devices tripping as they should. Our guide to [AFCI and GFCI](https://confluxcincinnatiknobandtube.com/guide/afci-and-gfci-on-knob-and-tube/) explains those devices.

## What happens to the old wiring?

We retire each old run once its replacement is live. We disconnect it at the panel end and at its last device or splice, test it dead, tag it and photograph it.

We can take out runs in open attics and basements; runs inside walls stay, disconnected. [Knob and tube removal](https://confluxcincinnatiknobandtube.com/knob-and-tube-removal/) shows how we make that record, and [active versus abandoned K&T](https://confluxcincinnatiknobandtube.com/guide/active-vs-abandoned-knob-and-tube/) explains why both ends matter.

## What do you get at the end?

IBI comes back for the final inspection. Once it passes, we patch the openings to the finish we agreed, and hand the job over with its records.

| Record | What it shows |
| --- | --- |
| Circuit map | Every circuit, the rooms it feeds and its status |
| Labeled panel directory | One line per breaker |
| Scope letter | What we replaced, what we disconnected, whether any K&T remains |
| Disconnection record | Each retired run, where we cut it, with photos |
| IBI permit final | Proof the work had a permit and passed inspection |
| Openings list | Every opening, with the patching scope |

Our guide to [rewiring timelines](https://confluxcincinnatiknobandtube.com/guide/how-long-does-it-take-to-rewire-a-house/) covers how long each stage takes and what stretches it, and [preparing for a rewire](https://confluxcincinnatiknobandtube.com/guide/preparing-for-a-rewire/) covers the household side. To start with your circuit map, call [(513) 496-2715](tel:+15134962715).

## Questions about this guide

### Does replacing knob and tube mean pulling the old wire out?

Usually not. We disconnect the old wire at both ends and leave it in walls we'd have to open plaster to reach. We can take out runs in open attics and basements. What inspectors and insurers care about is that it's dead and recorded, not that every piece of porcelain is gone.

### Can new wire be pulled through using the old wire?

Rarely. K&T is held by knobs and passes through tubes in the framing, so you can't use it to drag new cable along its path. New cable takes its own route, usually straight down from the attic or up from the basement into each wall cavity.

### Are outlets added when the house is rewired?

They can be, and the rewiring plan is where you decide. Kitchens, baths and rooms with electronics often get more outlets and their own circuits. Adding them while the routes are open costs far less than adding them later, so think about how you use each room now.

## More guides

- [Learn**How long does it take to rewire an old house?** Nobody can honestly give you one number. What you get is a sequence of stages, each with its own pace, and most families live at home through all of them.](https://confluxcincinnatiknobandtube.com/guide/how-long-does-it-take-to-rewire-a-house/)
- [Learn**How do you prepare for a house rewire?** Most of the preparation is decisions, not packing. Make them before the scope is final and the rest of the job runs more smoothly.](https://confluxcincinnatiknobandtube.com/guide/preparing-for-a-rewire/)
- [Learn**How does a Cincinnati electrical permit work for a rewire?** Who issues it, who can pull it, what the inspector looks at before your walls close, and what changes outside the city line.](https://confluxcincinnatiknobandtube.com/guide/cincinnati-electrical-permit/)
- [Decision Guide**Can knob and tube wiring be repaired, or does it have to be replaced?** Repair is a real option in a narrow set of cases. Here's how to tell whether yours is one of them.](https://confluxcincinnatiknobandtube.com/guide/knob-and-tube-repair-vs-replacement/)
- [Decision Guide**How do you compare knob and tube rewiring quotes?** Two honest quotes can be far apart because they price different jobs. Line them up by scope before you compare the totals.](https://confluxcincinnatiknobandtube.com/guide/comparing-rewiring-quotes/)

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