# Knob and tube vs cloth wiring: what is the difference, and which one is in your house?

> Knob and tube vs cloth wiring in older LA houses: how each was built, its era, why neither has a ground, and what it means for a rewire. Get circuits mapped.

URL: https://laknobandtube.com/guide/knob-and-tube-vs-cloth-wiring/

Both use cloth over rubber, so they get confused. They were built differently, come from different decades, and fail in different ways.

Last Updated: October 24, 2026

[LA Knob and Tube](https://laknobandtube.com/) replaces old wiring in Los Angeles, Pasadena, Glendale and South Pasadena, and the first question on many calls is knob and tube vs cloth wiring. The short answer: knob and tube is two separate wires run apart through open framing on porcelain knobs and tubes. “Cloth wiring” usually means early sheathed cable, two rubber-insulated wires wrapped together in one woven jacket and stapled to the wood. Both are old and usually ungrounded, but they age differently.

That difference matters because it changes how a house is assessed and, sometimes, what an insurer asks for. It rarely changes how the replacement is done: both are retired circuit by circuit and replaced with modern grounded cable, as the [replacement process guide](https://laknobandtube.com/guide/knob-and-tube-replacement-process/) describes.

Key takeaways

- Knob and tube: single conductors held apart on porcelain, open to the air
- Cloth-sheathed cable: two conductors bundled in one woven jacket, stapled to framing
- Both use rubber insulation under cloth, and the rubber is what ages
- Neither originally had a ground wire, and three-prong outlets do not prove one
- Many older LA houses could have both, plus modern cable from later remodels

## The two systems side by side

|  | Knob and tube | Cloth-sheathed cable |
| --- | --- | --- |
| How it is built | Two single wires, each on its own porcelain knobs, several inches apart | Two insulated wires bundled together inside one woven jacket |
| How it is fastened | Knobs nailed to framing; tubes through drilled holes | Stapled or strapped flat along joists and studs |
| Connections | Often soldered and taped splices in open air | Usually inside metal boxes |
| Cooling | Each wire sheds heat to open air | Wires sit together inside the jacket |
| Ground wire | None | Usually none in early cable; later versions sometimes had one |
| Era | Late 1800s into the 1930s | Roughly the late 1920s into the 1950s |

## How knob and tube is built

Knob and tube runs each conductor on its own. Along a joist, the wire is tied to small porcelain knobs that hold it off the wood. Through a joist or stud, it passes inside a porcelain tube. Near boxes and other tight spots, installers slipped a flexible cloth sleeve called loom over the wire. The hot and neutral of one circuit can travel along different joists and meet only at the fixture.

That separation was the safety idea: a damaged spot on one wire could not easily short against the other, and open air carried heat away. The [main knob and tube guide](https://laknobandtube.com/guide/knob-and-tube-wiring/) explains why the design held up for decades and what changed around it.

## How cloth-sheathed cable is built

Early nonmetallic sheathed cable put both conductors into one assembly. Each copper wire got its own rubber insulation, often a paper wrap, and then the pair was wrapped together in a woven cotton jacket treated to resist moisture. It went in faster than knob and tube, because one run of cable replaced two separate runs and dozens of knobs, and it connected inside boxes rather than at open splices.

Cable with a metal armor jacket, sometimes called BX, was also used in the same decades and turns up in some LA houses. It looks different, a spiral of steel, but it raises a similar grounding question, because the armor of older cable is not always a reliable ground path.

## Rubber and cloth insulation: what actually ages

In both systems, the cloth is not the insulation. The cloth protects the rubber underneath from abrasion. The rubber is what keeps the copper from touching anything, and rubber compounds of that era harden with heat and time. Left alone, hardened rubber can stay in place for decades. Bent, pulled or stepped on, it cracks and flakes off, and bare copper is left behind.

Where the two systems age differently is heat. Knob and tube conductors sit apart in open air, so they run cool unless insulation is piled around them. Cloth-sheathed cable holds two conductors side by side in a jacket, and where it runs through hot attics or is overloaded, the rubber between the wires can get hotter. Neither is a reason to panic. Both are a reason not to handle old wiring to see what condition it is in. The guide to [whether knob and tube is dangerous](https://laknobandtube.com/guide/is-knob-and-tube-wiring-dangerous/) covers the warning signs that matter.

## Grounding: neither system started with one

Knob and tube has no equipment grounding conductor at all. Early cloth-sheathed cable usually had two wires and no ground either. Cable carrying a ground wire appeared later, and grounding-type receptacles became the norm for new work around the 1960s. Some later cloth-jacketed cable did include a small ground, so the only reliable answer for a specific circuit is a test.

A three-prong outlet tells you nothing about either. Over the years, many two-prong outlets were swapped for three-prong ones without any ground being added. The guide to [three-prong outlets on knob and tube](https://laknobandtube.com/guide/knob-and-tube-three-prong-outlets/) explains what testing shows and what GFCI protection can and cannot do on an ungrounded circuit.

## Why both can show up in the same Los Angeles house

The Census Bureau counts 19.1% of homes in the City of Los Angeles as built before 1940, and 27.9% before 1950. A house in the first group was likely wired with knob and tube. A house finished in the 1940s may have cloth-sheathed cable from the start, or a mix, depending on the builder.

Then come the remodels, which the [active and abandoned wiring guide](https://laknobandtube.com/guide/active-vs-abandoned-knob-and-tube/) shows can leave old runs live in unexpected places. Where a pre-war house had a kitchen redone in the 1950s or a room added on the back, the new work was often cloth-sheathed cable, sometimes spliced straight into a knob and tube run in the attic. Later still came plastic-jacketed cable. LADBS permit descriptions in the City of LA include jobs that replaced knob and tube while upgrading a panel, which is a reminder that a house can carry several generations of wiring at once. Where a house has that kind of history, the useful question is not which system it has but which circuits run on which, and where the splices between them are. The [knob and tube inspection](https://laknobandtube.com/knob-and-tube-inspection/) maps exactly that.

## Is cloth wiring safer than knob and tube?

Not in a simple way. Cloth-sheathed cable has connections in boxes, which is an improvement over open splices, and it is less likely to have been tapped informally along the way. Knob and tube has better heat shedding, as long as nothing covers it. The weakest point in either is usually where someone joined new work to old, or where insulation, storage or a remodel disturbed the run.

California’s restriction on insulating over wiring is written for knob and tube specifically, under section 394.12 of the electrical code, which is covered on the [attic insulation page](https://laknobandtube.com/knob-and-tube-attic-insulation/). Old cloth cable buried in insulation is still a condition an electrician would want to look at before the attic is closed up.

## What it changes about replacement

For a rewire, the two systems are handled the same way. Each old circuit is identified, a new grounded circuit is run to the same rooms, usually with more outlets, and the old run is disconnected at both ends so it cannot be energized again. Runs that are easy to reach can be pulled out; the [removal page](https://laknobandtube.com/knob-and-tube-removal/) explains when that is worth doing.

The difference shows up in planning. Cloth-sheathed cable stapled along framing is sometimes easier to trace and occasionally useful as a guide for a new route. Knob and tube routes tend to split hot and neutral, which takes longer to map. A [partial replacement](https://laknobandtube.com/partial-knob-and-tube-replacement/) has to record both kinds of old circuit in the list of what remains. A [whole-house rewire](https://laknobandtube.com/whole-house-rewiring/) retires all of them.

## Looking without touching

From a safe distance, with a flashlight, the clue is spacing. Two single wires several inches apart on white porcelain are knob and tube. One flat or round woven cable, stapled along the wood, is cloth-sheathed cable. Do not move insulation, pull on wires or open boxes to check. The [identification guide](https://laknobandtube.com/guide/how-to-identify-knob-and-tube/) shows what to look for and where. When you want the circuits sorted properly, a call or an estimate request starts with a circuit map of the whole house.

## Questions about this guide

### Is every cloth-covered wire in an old house knob and tube?

No. Knob and tube is single wires run apart on porcelain. Cloth-sheathed cable bundles two insulated wires inside one woven jacket and is stapled to the framing. Both carry cloth over rubber, which is why they get mixed up.

### Does old cloth-sheathed cable have a ground wire?

Early versions usually do not. Some later cloth-jacketed cable carried a small ground conductor, so the only way to know is to test the circuit. A three-prong outlet on the end of it proves nothing by itself.

### Do insurers treat cloth-sheathed cable the same as knob and tube?

It depends on the carrier and how its application words the question. Ask your carrier or broker in writing whether its question covers cloth-sheathed cable as well as knob and tube, before the scope of a rewire is set.

## Related service

### Whole-house rewiring

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

## More guides

- 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 [Can you put three-prong outlets on knob and tube wiring?](https://laknobandtube.com/guide/knob-and-tube-three-prong-outlets/)What a ground wire does, why knob and tube never had one, and the options the electrical code allows for replacing two-prong outlets on old circuits.
- Learn [What is knob and tube wiring, and what should an LA homeowner do about it?](https://laknobandtube.com/guide/knob-and-tube-wiring/)How the system works, why it was a sound design in its day, what goes wrong with it now, and how Los Angeles owners decide what to do.
- Learn [How does knob and tube replacement work, from the first visit to the final inspection?](https://laknobandtube.com/guide/knob-and-tube-replacement-process/)Each stage depends on the one before it. Here is what has to be known before the next step starts, and where the path splits by house.