Rewiring Plaster and Drywall Walls: What to Expect

The short answer: a rewire does not mean tearing out your walls. In a typical Kansas City pre-war house with an unfinished basement and a reachable attic, most new cable is fished through the existing wall and ceiling cavities, and the openings are concentrated at outlet and switch locations, behind baseboards, and wherever a run has to pass a fire block. Openings may be limited, but concealed blocking and previous work can change the route. Finished basement ceilings, decorative plaster, tile, insulation and pre-1978 paint belong in the access plan, along with how unexpected conditions will be handled. This page explains what to expect, what the law requires, and what to settle in writing.

Why plaster houses are a different job

Most pre-war houses were built with plaster on wood lath — a wall that is strong, heavy, and unforgiving of vibration. About one in five housing units in both Kansas City, Missouri and Kansas City, Kansas was built before 1940 (Census ACS 2020–2024, B25034). As a rule of thumb, drywall became common after the Second World War, and plaster persisted into the 1950s in many builds.

Plaster matters for three reasons:

1. It’s attached by keys. Wet plaster was pushed through gaps in the lath and hardened into “keys” that hold it on. Hammering or reciprocating saws vibrate the lath, snap the keys, and loosen plaster well beyond the hole you meant to cut. Ask how the contractor will limit vibration and contain dust while working through the plaster and lath; tool choice and dust control belong in the professional work plan.
2. It’s thicker. “Old-work” boxes — the kind that clamp into a finished wall — and the fishing path have to account for lath plus two or three coats of plaster, roughly an inch in total.
3. It’s painted, and the paint is old. That brings in the lead rules below.

Drywall houses (late 1940s onward, and most remodeled rooms) are faster to open and cheaper to patch, but the fishing paths are the same.

Where the openings go

Openings land where the cable has to enter or leave a cavity: at every new box, at fire blocks, and at the top or bottom plate of a wall that can’t be reached from the attic or basement. A good crew puts them where devices, trim or furniture will hide them.

In balloon-framed houses — common in American housing before about 1930 — the stud bays often run uninterrupted from basement to attic. That makes fishing easier, but fire blocking may be missing where modern code expects it, and the contractor should confirm the required fire-blocking work with the inspector.

Who patches, and to what finish

Wall repair can be a separate scope and a substantial part of the budget. Get the finish level in writing. There are three normal arrangements, and none is “the” standard:

• Patching is included at a stated finish level. Rough filling, paint-ready preparation, texture and final paint are different deliverables. The knob-and-tube and whole-house scope checklists both call for those terms to be explicit.
• Electrician leaves the openings; a plasterer or drywall sub patches. Compare the separate repair price, finish standard, timing and responsibility before choosing this arrangement.
• Nothing included. Legitimate — but the bid must say so.

For reference on what separate repair runs nationally (not Kansas City figures): HomeAdvisor’s plaster-repair guide averages “$3,840” per project (range “$2,000 – $7,200”), and its drywall-repair guide averages “$612.” (HomeAdvisor plaster repair; HomeAdvisor drywall repair) Use those to recognize when a bid’s “patching included” line is carrying real cost, and when a lower bid has simply left it out. The estimate worksheet has a line for it.

Lead paint: what the law requires in a pre-1978 house

Paid renovation that disturbs painted surfaces in pre-1978 housing can require a certified firm and lead-safe work practices. The applicable program, scope and exemptions need to be assessed before cutting begins. Pre-1978 age does not prove that every surface contains lead, and a few small openings do not automatically exceed the area threshold. (EPA RRP program)

• Missouri: EPA administers RRP. Its minor-repair exception covers no more than six square feet of interior painted surface per room, subject to other conditions. Work in the same room within 30 days is combined. Window replacement, demolition of painted surfaces and prohibited practices do not qualify for that minor-repair exception. Removing a component can require counting its entire surface area. (EPA interpretation of minor repair and maintenance)
• Kansas: KDHE operates an EPA-authorized program. K.A.R. 28-72-52 uses six square feet or less per component in its minor-work exemption and incorporates federal renovation provisions. That is a different wording, not a reliable basis for calling one state’s rule universally stricter. A written determination by a certified inspector or risk assessor that affected components are free of lead paint is another listed exception. (Kansas regulations, 28-72-52)

Ask which surfaces will be disturbed, how their area is measured and why the firm considers the work covered or exempt. When covered, the plan should address containment, warning signs, dust-control methods, HEPA cleanup and cleaning verification. Ask for the current firm certification and the certified renovator responsible for the work. A contractor’s general electrical license is not a substitute for the applicable renovation certification.

Attic insulation and vermiculite

Two attic conditions change the plan. First, if knob-and-tube in the attic is still energized, it cannot legally be enveloped by loose, rolled or foamed insulation (NEC 394.12(5)); the attic circuits get replaced before any insulation project. Second, if the existing insulation is vermiculite — loose, lightweight, pebbly, grey-gold or brownish — EPA’s guidance is to assume it contains asbestos and not disturb it. More than 70 percent of all vermiculite sold in the U.S. from 1919 to 1990 came from a single mine near Libby, Montana, which was contaminated. (EPA, vermiculite insulation) If routing or access may disturb vermiculite, stop that part of the plan until an appropriately qualified professional evaluates the asbestos risk and the work method. Tell the electrician before the visit. A photo taken without entering or disturbing the material may help flag it, but a photo does not identify asbestos content or establish that the area is safe to disturb.

Ceilings, tile and the rooms you don’t want touched

Say which rooms are off-limits before the scope is written, not after the first hole. The routing plan can usually go around:

• Decorative or coved plaster ceilings — fed from above where the attic allows; fixture boxes replaced from the attic side.
• Tiled bathroom walls — receptacles and switches reached from the adjacent room or from below; the GFCI often lands on a non-tiled wall.
• A recently finished room — circuits routed through adjacent closets and the floor above/below; openings minimized at the cost of more fishing time, which the bid should show.
• A finished basement — the ceiling is the wiring highway for the first floor; expect a row of openings along the runs unless the ceiling has removable panels.

Not everything can be avoided. A ceiling box has to go where the fixture is. The point is that the plan says where, in advance.

Can you stay in the house?

Sometimes, with an agreed plan for essential services and separation from the work. Whether you can stay depends on circuit isolation, outages, dust containment, access and the household’s needs. Ask the contractor to identify:

• Which rooms and circuits remain usable during each phase.
• Whether safe power restoration is possible each evening, and what happens if it is not.
• The expected service outage and who coordinates reconnection after inspection.
• The containment boundaries, cleanup steps and times when occupants must stay outside the work area.

Children and pets need reliable separation from the work zone. Medical equipment, heating or cooling, food storage and a home office may require a different arrangement or temporary accommodation. Discuss those needs before accepting the schedule; a general promise to work room by room is not enough.

Planning checklist

Use this before the site visit and again before day one. A printable copy is at /assets/project-planning-checklist.pdf.

Access

• Basement: clear ordinary stored belongings from the planned access route; do not touch wiring or remove material attached to it.
• Attic: make the hatch accessible without disturbing insulation; disclose suspected vermiculite or other hazards and whether the attic is floored.
• Panel: remove stored belongings from the access area; ask the contractor to confirm required working clearances. Do not remove its cover.
• Meter and service entrance: accessible from outside; note fences, shrubs, dogs.
• Keys / lockbox / alarm codes arranged for inspection days.

Belongings

• Furniture pulled at least two feet off every wall in active rooms; pictures, mirrors and shelves down.
• Closets that will be used for openings emptied.
• Rugs rolled; floors in active rooms protected (ask who supplies the protection).
• Electronics and anything dust-sensitive moved out of active rooms or covered.
• Valuables and medications moved to a room not on the schedule.

Occupied rooms and off-limits rooms

• List the rooms that must stay usable (home office, nursery, a bedroom for an elderly relative) and the rooms that must not be opened (new finishes, decorative ceilings, tile).
• Agree the sequence room by room, with dates.
• Plan for children and pets on lead-containment days.

Interruptions

• Get the no-power days in writing (kitchen day; service-upgrade day).
• Refrigerator/freezer plan for the kitchen day; medical equipment plan if any.
• Internet / work-from-home plan for days the office area is active.
• Inspection dates and what happens to the schedule if one slips.

Wall repair

• Who patches; to what finish (rough / paint-ready / textured and painted).
• Who matches texture and paint; whether you’ll hire a plasterer directly.
• Approximate opening count by room, from the scope.
• Lead-safe certification number of the firm doing the cutting (pre-1978 house).

At the end

• Walk every room with the foreman; confirm every opening is on the list.
• Receive: permit number, final inspection record, itemized invoice naming circuits replaced, panel directory.
• Confirm no energized knob-and-tube remains (or exactly which circuits still do, for a partial job).

Frequently asked questions

Can a house be rewired without any holes?

Not realistically. Even the best fishing job needs an opening at each new box and wherever cable has to cross blocking. What a skilled crew does is keep the openings small, put them where they’ll be hidden, and cut plaster cleanly so the patches disappear. Claims of “no damage” mean “no damage you’ll notice,” and the bid should say what’s patched.

How many holes per room should I expect?

For a bedroom on a rewire: one opening per new receptacle (typically several, under current spacing rules), one per switch, one at the ceiling box, and sometimes one or two at blocking or plates. The count depends heavily on whether the room can be fed from the attic or basement. Ask for the estimated count in the scope.

Is it cheaper to just remove the plaster?

Compare complete scopes. Removing plaster can simplify cable access but adds demolition, disposal, any required hazard controls, replacement wall material, finishing and paint. Keeping it may require more electrical labor and localized repair. Neither approach is automatically cheaper for every house; obtain prices that include the wall work as well as the wiring. The cost guide provides an estimate worksheet.

Who is responsible if a patch cracks later?

The contract and workmanship warranty should name who is responsible, what cracking or finish defects are covered, and the period for reporting them. Do not assume a return visit or texture match is included unless it is written into the scope.

Does the electrician have to be lead-certified, or just the plasterer?

Check the firm and workers responsible for each covered disturbance. The electrician may cut painted surfaces and the repair contractor may disturb more during preparation. Ask both which tasks fall under the applicable program and request the required firm and renovator credentials. The electrical contractor’s certification does not automatically cover a separate repair firm.

Ready to see how your house would be handled? Get a Quote and tell us the year built, the wall type and the rooms you want left alone. For the whole decision — what wiring you have, how much needs replacing, permits, insurance, cost — start with the complete guide to rewiring an older Kansas City home. The service pages: knob-and-tube replacement · whole-house rewiring.