Knob-and-Tube Wiring on a Home Inspection (When It's a Deal-Breaker and When It Isn't)

What knob-and-tube wiring on a home inspection actually means

When a home inspection flags knob-and-tube wiring, the inspector is telling you the system is present — not that it's dangerous, and not that it's safe. The standard of practice tells inspectors to note K&T and refer you to a licensed electrician. They generally won't trace which circuits it powers or certify its condition, because that's outside the scope of a visual inspection.

The report is a prompt to investigate, not the final answer. What you do with it depends on three things a standard inspection usually can't tell you: whether the wiring is still energized, whether it's been modified or buried in insulation, and whether a carrier will insure the home as it stands. This guide walks those in the order that actually affects your decision.

K&T isn't dangerous just because it's old; plenty of it has run quietly for decades. The problems show up when later owners spliced modern circuits onto it without permits, packed attic insulation around it, or overloaded circuits sized for 1940s demand. At least one fire department has said publicly that it hasn't seen a trend of house fires caused by knob-and-tube — worth knowing for the sake of keeping your head clear. The carrier objection is mostly an underwriting decision, not a confirmed fire epidemic, but that doesn't make the insurance problem go away.

Active vs. abandoned: the distinction that drives cost and insurability

Not all knob-and-tube is doing the same job. Active K&T is still energized and powering circuits in the home. Abandoned (or "abandoned in place") K&T has been disconnected and left dead inside the walls after newer wiring took over.

This one distinction drives both the safety read and the cost. Active K&T feeding modern loads is the case carriers care about and the case that may need replacing. Abandoned, de-energized K&T is often acceptable to insurers and may not need to be removed at all, as long as no one packed insulation around it while it was still live.

The catch is that you usually can't tell which you're looking at. K&T can look dead in the basement and attic and still be energized behind plaster, because electricians often splice new wire onto an old run and leave the original wire live inside the wall. A home inspector can see the exposed portions; they can't trace what's hidden. Only a licensed electrician testing the circuits can tell you how much is live, how much is abandoned, and what it would take to deal with the rest. That test is the first thing worth paying for after the inspection flags K&T.

The one finding you shouldn't defer: insulation contact

One knob-and-tube combination deserves priority over the rest: K&T buried in or touching insulation, especially blown-in attic insulation.

Knob-and-tube was designed to run through open air, which lets the wires shed heat. Surround them with insulation and that heat has nowhere to go, which is the scenario most likely to cause trouble over time. A lot of older homes had attic insulation added decades after they were built, by people who had no idea live K&T was running underneath. If your inspection mentions both knob-and-tube and added insulation in the same space, treat that as the priority item for an electrician to look at, not something to fold into a someday list.

This is also where buyers find out the inspection didn't catch everything: insulation hides the wiring it's burying, so it's possible to close and discover active, insulation-covered K&T later. If the inspector didn't note it, that's frustrating, but inspector liability is usually limited to the cost of the inspection — so scope it now rather than count on a remedy after closing.

The part that actually decides this: insurance, then the lender

Most buyers research knob-and-tube as a fire question. The question that controls the deal is whether you can insure the home.

Many preferred carriers won't write a new policy on a house with active knob-and-tube. As one insurance broker put it bluntly in a local news interview, if K&T goes on the application, the policy gets declined. Some carriers will bind coverage on a condition — remove or de-energize the K&T within 30 to 60 days of purchase — and others write it with a surcharge that climbs until the work is done. Some buyers end up on a state FAIR plan or a surplus-lines policy: more expensive, narrower, and sometimes not acceptable to a lender.

That's the load-bearing issue: your mortgage lender requires a bound homeowners policy before they'll fund the loan. Without a policy there's no mortgage and no closing. The inspector and appraiser can both sign off, and the deal can still stall at the insurance step if you didn't see it coming. This is the same gatekeeper problem covered in depth in our guide on inspection findings that affect insurance and lending — knob-and-tube is one of the most common triggers on that list.

The move that protects you: call an independent insurance broker — not a single-carrier agent — with the inspection report in hand, and ask for a written indication of who will write the home and on what terms. Do it early in the contingency window, not the day before it closes.

Can you get a mortgage on a house with knob-and-tube?

Usually yes on paper, which is exactly what trips people up. FHA, Fannie Mae, and Freddie Mac generally permit knob-and-tube as long as the system functions properly, is safe, and meets a minimum service level (often cited as 60 amps). So buyers read that the loan program allows K&T and assume financing is clear.

That permission is often moot, because the private carrier's bar is higher than the loan program's. If no carrier will write a standard policy, it doesn't matter that the program allows the wiring — you can't satisfy the lender's insurance requirement, so the loan can't close. Treat "the loan program allows it" and "I can actually get this funded" as two separate questions. The lender-required repairs guide covers where loan requirements and inspection negotiations overlap.

What a rewire costs — and why the quotes vary so much

Costs depend on how much of the wiring is live, how accessible it is, and what kind of walls the house has. These are rough magnitudes, not quotes.

Partial or accessible-only work — replacing the runs you can reach in an open attic and basement, or a limited set of circuits — tends to land in the low-to-mid four figures. A whole-house rewire commonly runs into the low five figures, and climbs from there in plaster-walled older homes, where the real expense is opening and patching walls rather than the wiring itself.

The spread on the same house can be enormous — buyers routinely report one quote that's two or three times another for identical work, depending on wall access and how much finish repair is included. That's why no honest guide can hand you a single number. Get two or three local quotes from licensed electricians, and make sure they're scoping the same thing: partial vs. whole-house, with or without drywall or plaster repair. For how to think about repair numbers across your whole report, see thinking about repair costs.

The two clocks you're racing

Knob-and-tube is unusual because it puts you between two deadlines that don't line up.

The first is your inspection contingency window — often somewhere around 7 to 14 days — during which you can still negotiate or walk away with your earnest money protected. The second is the carrier's conversion clock: when an insurer binds coverage on a "remediate within 30 to 60 days" condition, that countdown starts after you close, and it can force you to schedule a five-figure rewire almost immediately after moving in.

These collide because the insurability question has to be answered before the contingency expires, but the rewire itself usually happens after closing. A buyer who waits until day eight of a ten-day contingency to call a broker may not get a written answer in time to make a safe decision. The fix is sequencing: get the electrician's scope and the broker's written insurability indication early, so that by the deadline you already know whether the home is insurable and what a rewire will cost. For the full sequence, see what to do before the inspection contingency expires.

What to ask the seller: rewire, credit, or escrow holdback

Once you know the scope and the insurance picture, you have three common ways to handle knob-and-tube with the seller. None is automatically right; the best one depends on your leverage and your timeline.

A rewire as a closing condition. You make completion of the wiring work — by a licensed, permitted electrician — a condition of closing. It's done before you own it, and the home is insurable on day one. The downside is that the seller controls the contractor, which can mean a lowest-bid rush job, and the work has to fit the closing timeline.

A price reduction or credit. The seller lowers the price or credits you at closing, and you handle the rewire yourself afterward. Many buyers prefer this, because you choose the electrician, the schedule, and the scope. The trade-off is that you're carrying the work — and the carrier's conversion clock — after closing, so the credit has to be large enough to cover local quotes.

An escrow holdback. Money is set aside at closing to pay for the work, bridging the gap when a rewire can't be finished before the closing date. Not every lender or title company allows these, so confirm it's an option early.

Sellers often already know the K&T is there and would rather not touch it, so expect to make the case. A documented inspection finding plus a broker's written "we can't insure this as-is" is strong leverage — it reframes the rewire from your wish into a requirement of the sale closing at all. Leverage shifts with the market: in a buyer's market or on a home that's sat, you have more room; in a hot market with backup offers, less. For the mechanics of asking, see how to negotiate after a home inspection and repairs vs. credit.

When knob-and-tube tips into deal-breaker territory

For most buyers, knob-and-tube is a negotiation, not a no. It tips toward deal-breaker in a few specific situations.

The clearest one is stacking. The buyers who describe K&T as the thing that would have made them walk almost always mean the rewire on top of everything else — a maxed-out down payment, other major findings, a budget with no room left. A low-five-figure rewire is survivable on its own for many buyers; the same number is the last straw when it lands on a pile. If the rewire cost stacks onto other repairs the home needs and pushes the total past what you can carry, that's a real reason to reconsider, not a failure of nerve.

It also tips when no carrier will write the home on terms you and your lender can accept and the seller won't move on price or repairs. At that point the deal may simply not be financeable for you — a clean, unemotional reason to walk that you can hand to your agent.

Walking away over knob-and-tube is legitimate when the insurance and the cash don't line up. So is buying: most K&T is curable and insurable with the right carrier, a one-time upgrade that leaves you with safer wiring than the house next door. Doing the work inside the contingency window is what lets you make that call with real numbers instead of a worst-case guess. If you're weighing it against other big-ticket findings, home inspection deal breakers and when to call a specialist put it in context.

What to do next

Note where the knob-and-tube was found and whether the inspector mentioned insulation contact. Then do two things inside your contingency window, in parallel: hire a licensed electrician to test the circuits and scope the work, and send the report to an independent insurance broker for a written indication of who will insure the home and on what terms. Those two answers — what it costs and whether you can insure it — turn knob-and-tube from a vague fear into a decision you can make before your deadline. For the broader electrical picture, see electrical issues on a home inspection.

InspectionTriage reads your full report and flags the findings that tend to drive insurance and negotiation conversations — knob-and-tube among them — with cost context and a prioritized action plan you can take to your agent. You'll still call the broker and the electrician; the point is to walk into those calls knowing which questions matter. See what's worth negotiating — free.