Old-House Wiring in St. Louis: Knob-and-Tube, Aluminum, and Your Panel
Revised July 27, 2026
What is knob-and-tube wiring, and is it dangerous?
The median home in the City of St. Louis was built in 1938 and 57.9% predate 1940 (Census ACS 2020–2024); St. Louis County’s median is 1969 with ~34% built 1960–1979. That means two different problems: the city is knob-and-tube country, the county is aluminum branch wiring (1965–73) and questionable-panel country. Existing knob-and-tube is legal and grandfathered — the real hazard is insulation covering it, which the electrical code prohibits, because it was designed to shed heat into open air. CPSC: pre-1972 aluminum-wired homes are 55× more likely to reach “Fire Hazard Conditions” (cover-plate screws at 300°F). ⚠️ CPSC closed its Federal Pacific investigation in 1983 without a conclusion either way. 100 amps is the code MINIMUM, not a deficiency — a load calculation decides. In the City you may NOT pull your own permit for a rewire or service change.
Keep reading ↓The median house in the City of St. Louis was built in 1938. Nearly 58% of the city’s housing went up in 1939 or earlier, per the Census Bureau’s five-year American Community Survey estimates.
In St. Louis County the median is 1969, and about a third of the housing stock was built between 1960 and 1979.
Those two numbers, both from the Census Bureau, mean the city and the county have completely different electrical problems hiding in their walls. City houses are knob-and-tube country. County houses are aluminum-wiring and questionable-panel country. Here’s how to tell what you have, what actually matters, and what you can ignore.
What is knob-and-tube wiring, and is it dangerous?
Knob-and-tube was the standard wiring method from roughly the 1880s through the 1940s — two separate conductors run several inches apart, supported by white porcelain knobs and passing through porcelain tubes where they cross framing. It has no ground wire, and its cloth-and-rubber insulation gets brittle with age. But the single biggest hazard isn’t age at all: it was engineered to shed heat into open air, so burying it in insulation is what makes it dangerous. The National Electrical Code prohibits concealed knob-and-tube in spaces filled with loose, rolled or foamed-in insulation for exactly that reason.
The city problem: knob-and-tube
A 1938 median puts the typical city house dead in the middle of the knob-and-tube era. If you own a brick house in south city, Tower Grove, Dutchtown, Baden or the north side, there is a genuine chance some original wiring is still in service somewhere in it.
Go look, and don’t touch anything. In an unfinished basement or attic you’re looking for white porcelain spools nailed to the joists with a single wire running through each, porcelain tubes where wire passes through wood, and — the giveaway — two separate wires running parallel several inches apart instead of one modern cable. The sheathing is cloth or rubber, often cracked.
The thing you are actually hunting for is knob-and-tube buried under or inside blown-in insulation. That is the combination the Code specifically bans, and it is the realistic fire scenario. It usually happens innocently: somebody insulated the attic decades after the wiring went in and had no idea it mattered.
Two more clues that you’re on an ungrounded system: two-prong outlets throughout the house, and no third slot anywhere.
So is it legal?
Yes. Existing knob-and-tube is generally grandfathered — the electrical code is not retroactive, and neither Missouri nor the federal government bans living with it. You are not breaking a law by owning it.
Where it bites is the moment you touch it. The Code permits knob-and-tube only as an extension of an existing installation, typically with the local inspector’s approval, and new installation isn’t allowed at all. Insulating over it is prohibited outright. The City of St. Louis enforces the 2017 edition of the National Electrical Code; St. Louis County runs on its own adopted edition, so confirm with the County before planning work out there.
The county problem: aluminum branch wiring
If your house went up in the late sixties or early seventies — which describes about a third of St. Louis County — your risk is different and better documented.
Between roughly 1965 and 1973, a copper shortage pushed builders to aluminum branch circuit wiring. The Consumer Product Safety Commission estimates about two million homes got it. And the CPSC finding is blunt: homes built before 1972 wired with aluminum are 55 times more likely to have one or more connections at outlets reach what the agency calls “Fire Hazard Conditions.”
That phrase has an actual definition, which almost nobody quoting the statistic bothers to include. It means the cover plate screws on a receptacle reaching 300°F, or sparks coming out of the receptacle, or the material around it charring.
The important nuance: the danger is at the connections, not in the wire itself. Aluminum expands, contracts and oxidizes where it terminates at a switch or outlet, and those spots turn into high-resistance hot spots over decades.
To spot it, look at the cable sheathing in your basement or at the panel for printed “AL” or “ALUMINUM,” and at conductor color — dull silver rather than copper.
CPSC accepts two permanent repairs short of a full copper rewire: COPALUM crimp connectors and AlumiConn connectors. What it does not accept as a permanent fix is ordinary pigtailing with twist-on wire nuts — which is unfortunately the cheap fix people are sometimes sold.
What your panel is telling you
Read the label on the outside of the panel. Do not remove the cover. The conductors feeding the main are energized and are not protected by any breaker inside that box — this is the one part of a house where amateur curiosity genuinely kills people.
Federal Pacific / FPE Stab-Lok. Here the internet is far more confident than the evidence, so here is the careful version. CPSC ran a two-year investigation and closed it in 1983 without reaching a conclusion, saying the data available did not establish that the breakers posed a serious risk — while also explicitly citing its budget and noting it had insufficient data to accept or refute the manufacturer’s test results. So: no recall, no finding of a defect, and no finding of safety either. Anyone who tells you CPSC cleared these, or that CPSC condemned them, is overstating. What is on the record since: a 2002 New Jersey class action concluded the manufacturer had issued UL labels to products it knew did not meet UL testing requirements, and at least one insurer — The Hanover — publishes guidance saying the safest course is full replacement of the panelboard.
Zinsco (also branded GTE-Sylvania or Sylvania-Zinsco) gets grouped with FPE, but be aware the evidence is weaker: there was never a CPSC investigation, and what exists is home-inspector field reporting rather than formal testing. Widely flagged, worth having looked at, not federally documented.
Fuse boxes: obsolete, not automatically unsafe
A fuse is a perfectly effective overcurrent device — arguably faster-acting than a breaker. A fuse box is mostly obsolete rather than inherently dangerous: low total capacity, few circuits, no ground, no modern arc-fault or ground-fault protection, and you have to keep spares.
The real hazard has a name, and it’s over-fusing. A 30-amp screw-in fuse physically fits the same socket as a 15-amp fuse. Somebody gets tired of a circuit tripping, puts in a bigger fuse, and the nuisance stops — because the protection stopped. A fuse protects the wire, not the appliance. Put a 30-amp fuse on wiring rated for 15, and the wire inside your wall becomes the weakest link and the thing that overheats.
The Code names this failure mode directly: screw-in Edison-base fuses are permitted only as replacements in existing installations where there is no evidence of over-fusing or tampering.
And there is a cheap fix almost no one mentions, because it doesn’t sell a panel. Type S fuses and adapters are made so tampering is difficult — the adapter screws into the existing fuseholder and cannot be removed, after which only a correctly-rated fuse will fit. An adapter kit costs very little and makes an old fuse panel tamper-resistant.
Do you actually need 200 amps?
Often, no — and this is where you’ll be told otherwise by people selling panels.
Amperage is your whole house’s simultaneous capacity, not a quality grade. The Code sets 100 amps as the minimum service for a one-family dwelling — a floor, not a deficiency. Whether you need more is decided by a load calculation, and there’s a specific method in the Code for existing homes that exists precisely to answer “can what I have carry what I want to add.” Plenty of existing houses calculate out in the eighties of amps and pass comfortably on a 100-amp service.
100 amps is genuinely fine when your heat is gas, the range, dryer and water heater are gas, there’s one central air unit, and no EV charger or hot tub. That describes an enormous number of St. Louis houses.
200 amps is genuinely driven by an electric range plus electric dryer plus electric water heater; central air added to an already-loaded panel; a heat pump, especially with electric backup heat, which counts at full nameplate in the calculation; a hot tub; and EV charging — a 48-amp charger alone claims a 60-amp circuit, which is most of the way through a 100-amp service.
Ask for the load calculation. A contractor who won’t run one and just quotes an upgrade is guessing on your dollar.
The permit rule that surprises St. Louis homeowners
This one is worth knowing before you plan a DIY weekend.
The City of St. Louis does let a homeowner pull an electrical permit — but you have to pass a short test given by the Building Division’s Electrical Section, the work must be on an owner-occupied single-family home, and it’s limited to a room addition, repair, or modification of an existing system. Then comes the line that matters: in the City’s own words, you may not apply for permits for service changes, rehab, or new construction — those require a licensed contractor.
Which means the two jobs this entire article is about — rewiring, and upgrading your service or panel — are precisely the two you cannot permit yourself. Application fee is $25; the Building Division is at 1200 Market.
St. Louis County also requires licensed electrical contractors registered with the County, with a homeowner exception tied to an examination. Confirm the current rules with County Public Works before relying on it.
Checking that your electrician is real
Missouri’s setup is unusual and worth understanding, because “licensed” means two different things here.
Since July 2019 Missouri has offered a statewide electrical contractor license — but it is optional, and it is a business credential rather than a replacement for local licensing of individual electricians. A statewide licensee can work in any jurisdiction without passing a local proficiency exam. Permits and inspections still happen locally; the state issues neither.
So verify in two places: the state license lookup at mopro.mo.gov, and then the local registration — a City of St. Louis certified electrical contractor license for city work, or County electrical licensing for county work.
Insurance, and the right you actually have
You will read a lot of confident claims about which insurers refuse to cover knob-and-tube. We’re not going to repeat any of them, because carrier underwriting guidelines are not published and every specific claim we found traced back to marketing content rather than a carrier document. Ask your own agent — that is the only reliable answer, and it’s free.
What we can tell you is a right Missouri law gives you. If an insurer cancels a policy, it must give at least 30 days’ written notice (10 for non-payment), and the notice must state the actual reason clearly and specifically enough that an ordinary person can identify the basis — vague language is expressly prohibited.
That letter is useful. If wiring is the reason, you now have it in writing, which is exactly what your electrician needs to scope the remediation the carrier wants.
What it costs, honestly
We looked for St. Louis rewiring figures from any credible source and could not find any. There is no government, academic or research-body data on residential rewiring costs — only home-services marketplaces.
For rough scale, those national marketplaces put full knob-and-tube replacement somewhere around $12,000 to $35,000, with a panel upgrade adding roughly $1,500 to $4,000 and wall repair another $1,000 to $5,000. Treat those as national estimates, not St. Louis quotes.
One local factor does push the repair line item up: St. Louis’s older housing is full of plaster walls, and opening and patching plaster costs meaningfully more than drywall. Get three itemized local bids and make sure each one separates the electrical work from the wall repair, because that is where quotes diverge most.
Frequently asked questions
Is knob and tube wiring still legal?
Existing knob-and-tube is generally grandfathered and legal to keep using — the electrical code is not retroactive, and Missouri has no ban. New installation is not permitted, extensions of existing runs require the local inspector’s approval, and covering concealed knob-and-tube with loose, rolled or foamed insulation is prohibited outright.
Can you live in a house with knob and tube wiring?
Yes, and a great many St. Louis households do — the median city home dates to 1938. Intact knob-and-tube that has not been buried in insulation, overloaded, or badly spliced can function. The realistic hazards are insulation covering it, brittle cloth insulation, amateur splices, and the absence of any ground.
How much does it cost to rewire a house with knob and tube?
No government or research source publishes rewiring costs. Home-services marketplaces put full replacement at roughly $12,000–$35,000 nationally, plus about $1,500–$4,000 for a panel and $1,000–$5,000 for wall repair. Those are national estimates, not St. Louis quotes, and plaster walls here push the repair side higher. Get three itemized local bids.
Is it worth buying a house with knob and tube wiring?
It can be, but price it in before you close. Have an electrician assess how much original wiring is still live, whether any of it is buried in insulation, and what the panel is. Also ask your insurance agent what they will require, since that answer varies by carrier and is worth knowing before your financing is committed.
Can I sell my house if it has knob and tube wiring?
Yes. There is no legal barrier to selling a home with knob-and-tube in Missouri. Expect it to surface in the buyer’s inspection, expect some buyers’ insurers to ask questions, and expect it to become a negotiating point. Having a recent electrician’s assessment in hand tends to help more than it hurts.
Can you run Romex off knob and tube?
This is exactly the work that requires a licensed electrician and a permit rather than a weekend. The code allows knob-and-tube only as an extension of an existing installation and typically requires the local inspector’s approval, and the splice between old and new is a common failure point when done improperly. In the City of St. Louis, rewiring counts as “rehab,” which homeowners cannot permit themselves.
How do I know if I have aluminum wiring?
Look at the cable sheathing in your basement or at the panel for printed “AL” or “ALUMINUM,” and at conductor color — dull silver rather than copper. Aluminum branch wiring was installed roughly 1965–1973, which covers about a third of St. Louis County housing. CPSC accepts COPALUM or AlumiConn connectors as permanent repairs; ordinary twist-on pigtailing is not accepted.
Do I need to upgrade from 100 amp to 200 amp service?
Often not. The electrical code sets 100 amps as the minimum service for a single-family home, and a load calculation — not the age of the house — decides whether you need more. If your heat, range, dryer and water heater are gas and you have one central air unit, 100 amps is frequently adequate. Electric heat, a heat pump, a hot tub or EV charging are what genuinely drive 200.
Are you an electrician working on St. Louis’s old housing? Nearly 58% of city homes were built before 1940 and a third of the county between 1960 and 1979 — which means knob-and-tube, aluminum branch wiring and panel work are steady, specialized demand here. Homeowners searching for someone who knows old houses should be able to find you. Listing your business takes a few minutes.
Need someone now? See our guide to choosing an electrician, or browse local pros on St Louis Near Me Directory.
Written by a dedicated team of St. Louis locals who live, work, and play right here in the St. Louis metro. Founder Lane Forman and team are committed to building the region’s most trusted directory by verifying listings and connecting local businesses with loyal customers across Missouri and Illinois.