electrical wiring & rewiring

Seventy-seven percent of the housing stock in St. Louis was built before 1960. More than half was built before World War II. That means the majority of homes in the metro were wired before central air conditioning was standard, before kitchens had more than one or two outlets, before anyone imagined a household pulling 200 amps, and in many cases before the electrical code required a ground wire at all.

The wiring in those homes is not just old. It is a specific set of materials and methods, each with its own failure pattern and fire risk, that modern code no longer permits in new construction. If your home was built before the 1970s and the wiring has never been updated, there is a reasonable chance it contains one or more of the following systems.

Knob-and-tube wiring (1880s through 1940s). Knob-and-tube uses individual copper conductors supported by porcelain knobs and passed through porcelain tubes where they cross wood framing. The insulation is rubber wrapped in cloth. It has no ground wire. The rubber insulation becomes brittle and crumbles with age, exposing bare copper on open wood framing. The system was designed for a handful of lights and maybe a radio. It cannot handle the electrical load of a modern household. It was engineered to dissipate heat in open air, which means blown-in attic insulation packed against active knob-and-tube runs creates a direct fire hazard. NEC Article 394 addresses this specifically. Most insurance companies in Missouri will not write or renew a homeowner’s policy on a home with active knob-and-tube wiring, or they will exclude electrical fire from coverage entirely.

Cloth-insulated wiring (1920s through 1960s). Cloth-sheathed nonmetallic cable replaced knob-and-tube in many homes but brought its own problems. The outer jacket is woven fabric, and the individual conductors are insulated with rubber wrapped in cloth. Over 60 to 80 years, the cloth sheathing frays, the rubber insulation dries out and cracks, and bare copper becomes exposed inside wall cavities. Rodents are attracted to the cloth sheathing and chew through it, compounding the exposure. Earlier versions lack a ground conductor. Some variants contain asbestos in the sheathing, which requires careful handling during removal. Insurance carriers increasingly flag cloth wiring the same way they flag knob-and-tube: as a condition requiring remediation before they will offer full coverage.

Aluminum branch circuit wiring (1960s through 1970s). During the copper shortage of the mid-1960s, builders switched to solid-conductor aluminum for 15A and 20A branch circuits. Aluminum expands and contracts more than copper with each heating and cooling cycle. Over time, this loosens connections at outlets, switches, and breaker terminals. Oxidation forms at the junction between aluminum wire and copper or brass device terminals, increasing resistance. The result is heat buildup at connection points. The Consumer Product Safety Commission found that homes wired with aluminum branch circuits are 55 times more likely to reach fire-hazard conditions at outlets and switches than homes wired with copper. Aluminum wiring does not always require full replacement. In some cases, approved remediation methods (copper pigtailing with COPALUM or AlumiConn connectors at every device) can bring the system into a safe condition. We evaluate each home individually.

Ungrounded circuits with two-prong outlets. Any home wired before the 1962 NEC may have circuits that lack a grounding conductor entirely. The visible sign is two-prong outlets throughout the house. Without a ground, there is no safe path for fault current, which means no protection from electrical shock if an appliance develops an internal fault. Three-prong adapters plugged into two-prong outlets do not create a ground path. They create the appearance of one, which is worse. Rewiring these circuits with modern grounded cable is the correct fix. In limited cases, replacing ungrounded outlets with GFCI-protected receptacles provides shock protection without full rewiring, but it does not provide an equipment ground for surge protectors or devices that require one.

Decades of unpermitted modifications layered on top of all of the above. In homes with pre-war wiring, it is common to find modern Romex spliced directly onto cloth-insulated cable without a junction box, fuses replaced with oversized ones to stop nuisance blowing, circuits tapped for additional outlets without increasing wire gauge, and extension cords run through walls as permanent wiring. Each of these modifications compounds the risk of the original system. A rewire addresses the original wiring and the accumulated modifications together.

Pure Home Electric provides electrical rewiring services for homeowners throughout the St. Louis metro, including St. Louis City, St. Louis County, and St. Charles County. We remove and replace knob-and-tube, cloth-insulated cable, and aluminum branch circuits. We rewire entire homes and individual rooms. We bring ungrounded systems up to current code. And we handle the permits and inspections required by your municipality.

Call (314) 649-8687 for a free estimate.

Rewiring work in the St. Louis metro requires an electrical permit and inspection in virtually every jurisdiction. St. Louis City, St. Louis County, and St. Charles County all require permits for work that adds, modifies, or replaces circuits. The permit ensures the installation is inspected for code compliance before the walls are closed.

The inspection covers conductor sizing, proper box fill, GFCI and AFCI protection, grounding and bonding, outlet and switch placement, and the condition and labeling of the panel. We schedule inspections at the right point in the project (after rough-in wiring but before drywall) and stay on site during the inspection.

We pull the permit as part of every rewiring project. Unpermitted electrical work creates real problems: insurance companies can deny fire claims if the wiring was modified without a permit, and unpermitted work disclosed (or discovered) during a home sale can delay or kill a transaction.

Whole-Home Rewiring

A whole-home rewire replaces every branch circuit in the house: every wire running from the panel to every outlet, switch, light fixture, and hardwired appliance. The old cable is pulled out and new NM-B (Romex) copper cable is run throughout the home. Every outlet is replaced with a grounded, tamper-resistant receptacle. Every switch is replaced. The panel is typically upgraded as part of the scope (most homes that need rewiring also have panels that are undersized, obsolete, or both).

Whole-home rewiring is the right scope when the existing wiring is knob-and-tube throughout, when cloth-insulated cable is deteriorated to the point that patching individual circuits is not practical, when the home is being gutted for a major renovation and the walls are already open, or when an insurance company has required full replacement as a condition of coverage.

The process involves accessing wire paths through the attic, basement, crawlspace, and wall cavities. In homes where walls are remaining intact (not being opened for renovation), we use fish tape and drill access points to pull new wire through existing stud bays. This minimizes drywall damage, but some patching is unavoidable. We repair access points but do not handle full drywall finishing or painting. If the rewire is part of a larger renovation where walls are already open, the wiring goes in before drywall, which is faster, less expensive, and produces a cleaner installation.

Whole-home rewiring for a typical St. Louis area home runs between $8,000 and $25,000 depending on the size of the home, the accessibility of the wire paths, whether the walls are open or closed, and whether the scope includes a panel upgrade. A 1,500-square-foot brick bungalow with a basement and accessible attic is on the lower end. A 3,000-square-foot multi-story home with plaster walls and limited access points is on the higher end.

Basement and Remodel Wiring

Basement finishes and room additions are the most common trigger for partial rewiring in St. Louis homes. A finished basement needs dedicated circuits for the bathroom (20A, GFCI protected), adequate general-use receptacle circuits to meet the NEC spacing requirement (no point along a wall more than 6 feet from a receptacle), lighting circuits, and often a dedicated circuit for a sump pump, a bar area, or a home theater setup.

When the basement is unfinished and the joists are exposed, the wiring goes in before the framing and drywall. This is the simplest and least expensive scenario. When the basement is already finished and the remodel involves reconfiguring the layout, existing circuits may need to be rerouted, extended, or replaced entirely. We evaluate the existing wiring condition as part of the remodel scope. If the home has cloth-insulated cable or aluminum wiring feeding circuits that pass through the remodel area, the right move is to replace those circuits while the walls are open rather than leaving degraded wiring sealed behind new drywall.

Room additions require new circuits run from the panel (or a subpanel) to the new space. Under the 2023 NEC, most living areas in a dwelling unit now require AFCI-protected circuits, and all kitchen and bathroom receptacles require GFCI protection. We wire all remodel and addition work to the current code edition adopted by your municipality, not to whatever code was in effect when the house was originally built.

Kitchen and Bathroom Electrical Upgrades

Kitchens and bathrooms have the most demanding electrical code requirements of any rooms in a home, and they are the rooms where outdated wiring creates the most immediate safety risk because of the proximity of water and high-draw appliances.

A kitchen rewire or upgrade typically includes two or more 20A small-appliance branch circuits serving countertop receptacles, dedicated circuits for the refrigerator (20A), dishwasher (15A or 20A, GFCI protected), garbage disposal (15A or 20A, GFCI protected), range or cooktop (40A or 50A, 240V), built-in microwave (20A), and lighting circuits. Under the 2023 NEC, every receptacle in a dwelling-unit kitchen requires GFCI protection, and kitchen circuits require AFCI protection. Countertop receptacles must be spaced so no point along the countertop is more than 24 inches from a receptacle.

A bathroom electrical upgrade includes a dedicated 20A circuit for receptacles (which can serve multiple bathrooms but cannot serve other room types), GFCI protection on all receptacles, proper exhaust fan wiring, and lighting. If the bathroom has a heated floor, a towel warmer, or a whirlpool tub, each of those may require additional dedicated circuits.

Kitchen and bathroom rewiring often uncovers the worst of a home’s existing wiring because these rooms have the highest moisture exposure and the most appliance load. We frequently find cloth-insulated cable with crumbled insulation behind kitchen cabinets, ungrounded outlets within reach of kitchen sinks, and two-prong bathroom outlets with no GFCI protection.

Garage and Detached Structure Wiring

Detached garages, workshops, sheds, accessory dwelling units, and pool houses each need their own feeder circuit from the main panel (or a subpanel), properly sized for the intended load and run in appropriately rated cable or conduit. Underground runs between buildings require UF-B cable or individual conductors in PVC conduit buried to the NEC-required depth (typically 18 inches for UF-B, 12 inches for PVC conduit with GFCI protection).

Inside the structure, the NEC requires at least one receptacle per car bay in a garage, GFCI protection on all garage receptacles, and a dedicated circuit for a garage door opener. Workshop loads (table saws, air compressors, welders) may require 240V dedicated circuits. EV charger installations in detached garages require a properly sized feeder and a dedicated circuit at the charger location. We cover EV charger wiring in detail on our dedicated circuit page.

If the detached structure is already wired, the existing wiring should be evaluated for condition and code compliance before adding new loads. Extension cords run from the house to a detached garage are not wiring. They are a code violation and a fire hazard, and they are surprisingly common in St. Louis homes that predate attached garages.

Outdoor and Exterior Electrical

Exterior electrical work covers outlet installation on decks, patios, and building exteriors, landscape lighting circuits, post lights, security lighting, pool and hot tub wiring, and exterior panel or subpanel installation.

All outdoor receptacles must be GFCI protected and installed in weather-resistant, in-use covers (the bubble type that allows a cord to remain plugged in while the cover is closed). Outdoor wiring must be run in approved conduit or rated for direct exposure (UF-B for underground, NM-B is not rated for exterior or underground use). Circuits for pools and hot tubs have additional NEC requirements for bonding, disconnect placement, and clearance distances.

The NEC requires at least one GFCI-protected outdoor receptacle at the front and back of every dwelling unit, accessible from grade level. Many older St. Louis homes have no exterior outlets at all, or they have ungrounded outlets with no weather covers mounted in deteriorating metal boxes. Bringing exterior electrical up to current code is a straightforward project that eliminates the need for extension cords run through windows and doors.

Outlet and Switch Installation and Replacement

Individual outlet and switch work is the smallest scope of rewiring, but it is also the most common first step homeowners take when they realize their electrical system needs attention.

Outlet replacement covers swapping two-prong ungrounded outlets for grounded three-prong receptacles (which requires confirming or installing a ground conductor), upgrading standard outlets to tamper-resistant (TR) receptacles (required by the NEC in all new and replacement installations in dwelling units), adding GFCI outlets in kitchens, bathrooms, garages, basements, and outdoor locations, and installing USB outlets, 20A outlets for high-draw appliances, or 240V outlets for window AC units and shop equipment.

Switch replacement covers upgrading worn or damaged toggle switches, installing dimmer switches (which require a neutral conductor in the switch box under the 2011 and later NEC), adding three-way or four-way switches for multi-point lighting control, and installing smart switches (which also require a neutral conductor).

A note on GFCI retrofits in ungrounded systems: the NEC permits replacing an ungrounded two-prong outlet with a GFCI receptacle marked “No Equipment Ground.” This provides shock protection (the GFCI will trip on a ground fault) but does not provide an equipment ground for surge protectors or devices that require one. It is a legitimate code-compliant solution for locations where running a new ground conductor is not practical, but it is not the same as rewiring the circuit with grounded cable. We explain the difference during the estimate so you can make an informed choice.

Individual outlet or switch replacement typically runs $80 to $250 per device, depending on the type of device, whether the existing box needs to be replaced, and whether a new circuit or ground conductor is required. Multiple devices replaced in the same visit reduce the per-device cost.