What is knob-and-tube wiring and where is it found?
Knob-and-tube (K&T) was the standard residential wiring method in the United States from approximately 1880 through the late 1940s. It features individual copper conductors run through walls and ceilings, suspended on ceramic porcelain insulating knobs and directed through framing studs via porcelain tubes.
In Western Washington, active or abandoned K&T wiring is prevalent throughout historic neighborhoods in Tacoma (North End, Proctor, Lincoln), Olympia (South Capitol, Westside), Centralia and Chehalis (historic Edison and Hillside districts), and coastal hubs like Aberdeen and Hoquiam.
Unlike modern non-metallic sheathed cable (Romex), knob-and-tube is an ungrounded two-wire system. It contains a hot and a neutral conductor, but lacks an equipment grounding wire to protect modern three-prong electronics and prevent accidental electric shock.
Key hazards of knob-and-tube wiring
Knob-and-tube wiring was originally designed to dissipate electrical heat into open wall cavities and uninsulated attic spaces. Modern home improvements and heavy electrical demands create severe safety hazards:
Attic Insulation Contact
When weatherization programs blow cellulose or fiberglass insulation into attics over live K&T wires, heat cannot escape. Trapped heat bakes the rubberized cloth jacket, leaving bare conductors exposed against combustible wood framing.
Modern Circuit Overloading
Original K&T circuits were designed for a few 60-watt light bulbs. Modern households plug in microwave ovens, space heaters, computers, and appliances that easily overload 15-amp circuits, causing overheated wires inside walls.
Lack of Equipment Ground
Without a ground path, surge protectors cannot protect sensitive electronics. Homeowners often replace original two-prong outlets with three-prong receptacles without GFCI protection, creating false ground hazards.
Amateur Splicing & Modifications
Over eight decades, DIY homeowners frequently tapped into knob-and-tube runs with modern wire using electrical tape instead of approved junction boxes. These hidden flying splices spark and smolder inside walls.
Why insurance companies cancel policies over knob-and-tube
Homeowners insurance carriers in Washington State view active knob-and-tube wiring as an unacceptable fire underwriting risk. Major national and regional carriers including State Farm, Farmers, Allstate, and Liberty Mutual routinely deny property coverage on homes with active K&T circuits.
During the purchase process, insurance companies require the buyer to complete a 4-point inspection or electrical questionnaire. If the inspector confirms active knob-and-tube, the insurance company will either refuse to issue a binder or require full replacement within 30 days of closing.
Because mortgage lenders require active hazard insurance before releasing purchase funds, an unaddressed knob-and-tube finding can delay or completely kill a home closing.
Knob-and-tube replacement costs in Western Washington
Replacing knob-and-tube wiring requires fishing modern grounded Romex cable through walls and ceilings back to the main electrical panel. Costs vary depending on home square footage, crawl space access, and wall materials.
| Project Scope | Typical Cost Range | Key Factors & Requirements |
|---|---|---|
| Partial Rewiring (Attic / Crawl Space) | $3,500 – $7,000 | Replaces exposed knob-and-tube in accessible attics and crawl spaces prior to insulation work. |
| Whole-Home Rewire (Drywall Home) | $8,000 – $14,000 | Complete replacement of all circuits, modern grounded outlets, GFCI/AFCI breakers, and L&I electrical permits. |
| Whole-Home Rewire (Historic Plaster & Lath) | $12,000 – $22,000+ | Includes careful wire fishing through brittle lath-and-plaster, drywall patching, and 200-amp panel upgrade. |
How to handle knob-and-tube under Washington Form 35R
When your inspection report reveals active knob-and-tube wiring, you can use NWMLS Form 35R to protect your financial interests:
- Request full seller replacement prior to closing: Require that a licensed electrical contractor rewire all active knob-and-tube circuits, pull required Washington Department of Labor & Industries (L&I) permits, and provide a final inspection certificate before closing.
- Negotiate a price reduction or closing credit: Obtain a formal quote from a reputable licensed electrician and request an equivalent credit toward your closing costs so you can hire your own electrical team.
- Terminate under your inspection contingency: If the seller refuses to remediate or credit the rewiring cost, Form 35R enables you to walk away with your full earnest money deposit returned.