Knob and Tube Wiring on Long Island: Insurance, Risks, and What Replacement Costs

Knob and tube is the original residential wiring system used in homes built from roughly 1880 to 1945. The name comes from two components: ceramic knobs that hold the wires to framing members at intervals, and ceramic tubes that protect wires passing through framing holes.

The system runs individual conductors — a hot wire and a neutral wire — separately through the structure with air space between them. There is no ground wire. There is no cable sheathing. Everything is exposed single-conductor wire, insulated with a rubber compound that was suitable for the loads of the 1930s but was never designed to last indefinitely or carry the electrical demand of a modern home.

On Long Island, the concentration of knob and tube is highest in the pre-war housing stock of Nassau County — particularly in the older neighborhoods of Hempstead, Garden City, Mineola, and the Five Towns — and in the older sections of Suffolk County towns like Huntington, Amityville, and Patchogue. Many of these homes have been renovated multiple times, with knob and tube surviving in attics, walls, and basements even when other systems were updated.

The most immediate problem for most Long Island homeowners is not electrical safety — it's insurance.

Most New York homeowners' insurance carriers have stopped writing or renewing policies on homes with active knob and tube wiring. The policies they do write typically exclude electrical fires caused by knob and tube. In 2024 and 2025, we have seen carriers require written certification from a licensed electrician confirming that knob and tube is not in use as a condition of continued coverage — and when the electrician finds active circuits, the carrier gives the homeowner 30 to 60 days to remove it or face non-renewal.

This matters enormously at the point of sale. Mortgage lenders increasingly require electrical inspection as a condition of underwriting, and buyers' agents on Long Island now routinely ask about wiring type before making offers. We have been called in on half a dozen transactions in the past year where knob and tube wiring nearly killed the deal.

The insurance industry's position is driven by two things: the age of the insulation and the lack of grounding. Rubber insulation that is 70 to 100 years old becomes brittle, cracks, and can arc. The absence of a ground wire means there is no fault path — an appliance with a short goes live instead of tripping a breaker.

Beyond insurance, there are genuine safety concerns that have gotten worse over time.

Insulation degradation. The original rubber insulation on knob and tube was rated for decades, not a century. In homes that still have original wiring, the insulation has often deteriorated to the point that it cracks when touched. Where wire staples, joists, or other materials press against the wire, insulation wears through entirely. This is how arc faults start.

No grounding. Knob and tube is an ungrounded two-wire system. Modern appliances — particularly electronics, medical equipment, and anything with a three-prong plug — rely on the ground path for safety. Running them from ungrounded outlets either requires an adapter (which defeats the purpose) or means the equipment is operating without proper fault protection.

Overloading. The circuits were designed for the electrical loads of a 1930s home: a few light bulbs, maybe a refrigerator, a radio. They were typically fused at 15 amps. A modern kitchen, home office, or finished basement can pull multiples of that on a single circuit. We see overloaded knob and tube circuits — identified by melted insulation near junction boxes — on nearly every older Nassau County home where the wiring was extended rather than replaced.

Inappropriate modifications. Many older Long Island homes have knob and tube that was spliced into or extended with modern Romex at some point. These splices are often made in wall cavities without junction boxes, which is a code violation, and the different wire gauges create resistance points that generate heat.

A complete rewiring means pulling all existing knob and tube circuits and replacing them with properly grounded, code-compliant wiring. On a typical Long Island Cape or Colonial, that means:

• Pulling a permit with Nassau or Suffolk County. Rewiring is a permitted electrical job. Any contractor telling you otherwise is unlicensed or planning to skip required inspections.
• Panel assessment. Most homes that still have knob and tube also have undersized panels — 60-amp or 100-amp service — that won't support a modern home's load. A rewire is often combined with a panel upgrade to 200-amp service.
• Selective attic and wall access. We fish new wiring through existing wall cavities where possible, using flexible drill bits and fish tape. In most cases we can route new circuits without opening every wall. Attic runs are fully accessible. Basements are accessible from below.
• Coordination with PSEG if a service upgrade is included. PSEG schedules a brief utility cutover; this is typically same-day.
• Final inspection by the local building department before the permit is closed.

The work is disruptive — we're in and out of walls, running wire through the house — but it doesn't typically require full demolition. On a 1,500 to 2,000 square foot Cape or Ranch, we complete most rewires in two to three days.

Rewiring costs depend on square footage, number of circuits, whether a panel upgrade is included, and how accessible the existing wiring routes are. Typical 2026 ranges for Nassau and Suffolk County:

The difference between partial and full rewiring is significant. A partial rewire — removing accessible knob and tube from attic runs and the basement, leaving in-wall runs in place but confirming they are de-energized — is sometimes accepted by insurers and satisfies lender requirements in a pinch. But it leaves old wiring in place, does not solve the grounding problem, and will need to be finished eventually. We recommend full rewires on any home where the goal is long-term insurance coverage and modern electrical safety.

If you know or suspect your home has knob and tube wiring, the right sequence is:

1. Get an inspection. A licensed master electrician can identify which circuits are knob and tube, whether they are active, and what the scope of replacement would be. We provide written inspection reports that satisfy most insurance carrier requests.

1. Get a quote that includes permits. Never accept a rewire quote that doesn't include permit fees as a line item. Any job done without permits leaves you with no inspection record, potential title issues when you sell, and no protection if something goes wrong.

1. Ask about the panel at the same time. If the panel is 60 or 100 amps, combining the panel upgrade with the rewire saves mobilization cost and a second PSEG coordination.

1. Notify your insurer after completion. Once the final inspection is passed and the permit is closed, get the certificate of completion from the building department. Your insurer will want documentation.

We work in Nassau and Suffolk County, pull our own permits, and coordinate directly with the building departments and PSEG. If you want a written quote or inspection report, that's what our free estimate call covers.

A few workarounds homeowners ask about that do not actually resolve the insurance or safety issues:

AFCI breakers. Arc fault circuit interrupter breakers protect against arc faults on the breaker end but do not address degraded in-wall insulation or the absence of grounding. Most insurers do not accept AFCI installation as a substitute for knob and tube removal.

GFCI outlets. GFCI outlets at the first outlet in a circuit provide shock protection downstream but do not ground the system and do not address insulation condition.

Covering the wiring. Insulating over knob and tube — a common mistake made during attic insulation jobs — is actually a code violation. The system requires air circulation to dissipate heat. Blown insulation packed around knob and tube wire is one of the most common causes of attic electrical fires on Long Island.

The only permanent solution is replacement.