Knob and tube wiring replacement cost, and is it safe?

How much does it cost to replace knob and tube wiring?

Block Renovation's national cost guide adds up to $12,700 to $27,900 for the whole job on a 1,200 to 2,000 sq ft home. Integra Electrical, an electrician in Des Moines, Iowa, lists $16,000 to $32,000 for the rewire alone on 1,600 sq ft. Your own bid decides where you land. The International Association of Certified Home Inspectors (InterNACHI) says the wiring is "likely to be a safety hazard due to improper modifications and the addition of building insulation." Before your deadline, get a licensed electrician's written bid and your insurer's answer, then ask the seller for the rewire or a credit that matches the bid.

Key takeaways

• If only a few old runs remain, replacing just those costs $2,000 to $8,000.
• Block Renovation says carriers treat the rewire as "a maintenance and upgrade expense rather than a covered loss," and some only write a policy if the work gets done within a set window.
• Kitchens, bathrooms, laundry rooms and outdoor circuits are where InterNACHI says ungrounded knob and tube should not be used. Ask the electrician about those rooms first.

Is knob and tube wiring safe?

Insulation is the big risk. InterNACHI says "Insulation around K&T wires will cause heat to build up, and this creates a fire hazard." The system also "has no ground wire," and older runs are insulated with materials "susceptible to deterioration." Where the wiring is brittle or cracked, InterNACHI says "it should be replaced."

InterNACHI's advice is to "Have the system evaluated by a qualified electrician." When the electrician comes, ask three things:

• How much of the house is still on knob and tube?
• Has it been modified, spliced, or buried in insulation?
• What would a full or partial rewire cost, in writing?

How to get repair estimates during the inspection period covers getting that visit booked fast.

Does knob and tube wiring have to be replaced?

Not everywhere. InterNACHI says "While it is considered obsolete, there is no code that requires its complete removal." It also "is not permitted in any new construction" and "is treated differently in different jurisdictions." "In some areas, it must be removed at all accessible locations, while others don't."

Your local building department or a licensed electrician answers for this address.

What's in the full cost?

Four lines, all from Block Renovation's national guide. Block says most knob and tube homes need the panel upgrade.

Add the four lines and you get the national total above. The Des Moines electrician's rewire-only figure runs higher, and it says plaster walls and limited crawl space push costs up. Ask every bidder which of the four lines their number includes.

Can I get homeowners insurance with knob and tube wiring?

Maybe. American Family Insurance puts it plainly: "Some providers will offer coverage for knob and tube wiring while others will deny you outright." If one does, "you could face higher premiums."

InterNACHI adds that "exceptions are sometimes made for houses where an electrical contractor has deemed the system to be safe." Call your insurer with the address before your contingency closes. Ask whether an electrician's written evaluation would change its answer, and whether it requires the rewire within a set time. Get quotes from other insurers if it still says no.

What should I ask the seller for?

Put the electrician's scope and bid in the request. InterNACHI tells buyers the same: "get an estimate of the cost of replacing K&T wiring" and use it "to negotiate a cheaper price for the house." Until the bid arrives, treat the total above as a planning range, not your ask.

A request line: "Replace all knob and tube wiring by a licensed electrician, with permit and final inspection, including panel upgrade and wall repair, per the electrician's written quote." Add the bid figure as soon as you have it. What to ask for after a home inspection shows how this line fits with the rest of your list. The buyer repair request letter template gives the wording around it.

What if the seller says no?

Go back to your two answers. If the bid is more than you can carry, or no insurer will write a policy at this address, leaving may be the right call. When to walk away after a home inspection walks through that decision. Your contract sets the exact dates and terms for cancelling, so confirm them with your agent or attorney.

Is replacing only part of it enough?

Sometimes. If the house was partly rewired before, only the leftover runs need work. Block Renovation says insurers usually want documentation that the old circuits "were fully disconnected at the panel." It warns that "energized original circuits can survive for decades behind walls nobody opened." If the seller says the house was rewired, ask for the electrician's paperwork, then have your own electrician confirm no old circuits are still live.

How long does a knob and tube rewire take?

Block Renovation puts the electrical work at 3 to 10 working days on a typical home, and 2 to 3 weeks on larger or harder-to-reach ones. Wall repair and paint come after that. If the seller agrees to do the work, ask for the permit and the final inspection sign-off before closing.

How do I know what the rest of my report is worth?

Get written bids for the knob and tube and any other safety item. For everything else, Kept prices every line of an inspection report for $79, usually under 4 hours.

If your deadline is days away, upload your report to Kept and spend that time getting the electrician through the door.

Sources

• InterNACHI, "Knob-and-Tube Wiring"
• Block Renovation, "Knob and Tube Wiring Replacement Cost Guide"
• American Family Insurance, "Does Homeowners Insurance Cover Electrical Wiring?"
• Integra Electrical, "How Much Does Knob and Tube Wiring Replacement Cost"