Knob and Tube Wiring in New Hampshire

What Is Knob and Tube Wiring?

Knob and tube wiring is the original electrical system of American houses, installed from the 1880s through to around 1950, and a great deal of it is still in service in New Hampshire because the houses it was installed in are still standing.

It works quite differently from anything installed since. Two separate conductors, a hot and a neutral, run apart from each other rather than bundled together in a cable. Ceramic knobs hold them clear of the framing and ceramic tubes protect them where they pass through joists and studs. The separation is deliberate, since air between the conductors was the insulation, and the system was designed to shed heat into open air.

For its era it was competent work, and plenty of it was installed to a standard that puts some modern work to shame. The problem is not that it was badly made. The problem is that the assumptions it was built on stopped being true.

It has no grounding conductor, because grounding was not a requirement when it was installed. Its rubber and cloth insulation has now had seventy to a hundred and forty years to become brittle. And it was designed for a house with a few lights and a radio, not for a house with a kitchen full of appliances.

It turns up right across New Hampshire, in the older wards of Manchester and Concord, in Victorian Keene, and in the farmhouses around Henniker, Hopkinton, Warner, Bradford and Deering.

How Do You Know If a New Hampshire House Has Knob and Tube Wiring?

The ceramic is the giveaway, and the places to look are the unfinished ones. In a basement or a crawlspace, look along the joists for white or brown ceramic knobs holding single wires clear of the wood, and for ceramic tubes where a wire passes through a joist. In an attic, look for the same thing running across or through the framing, often disappearing under later insulation.

The wires themselves are single conductors running separately, typically a few inches apart, with cloth-covered or rubber insulation rather than modern plastic. Where the insulation has aged badly it can be cracked, crumbling or missing entirely, sometimes with bare conductor visible.

Two things commonly mislead people. Two-prong outlets suggest an ungrounded system but do not prove knob and tube, since early cable systems were also ungrounded. And a house that was partly rewired in the 1970s can have modern wiring in the obvious places and original knob and tube still live in the walls and ceilings nobody opened. Partial rewiring is extremely common in New Hampshire housing stock and it is why an attic that looks modern proves less than people assume.

If you are looking at pre-1950 stock anywhere from Manchester's older wards to the farmhouses around Henniker, Hopkinton, Warner and Bradford, the question is worth asking properly rather than by eye.

Is Knob and Tube Wiring Dangerous?

Not inherently, and that answer disappoints people on both sides of the argument. Knob and tube that is undisturbed, correctly fused, not buried in insulation, not extended by amateurs and not carrying more than it was designed for is not an emergency. There is a reasonable amount of it in New Hampshire doing exactly that.

What makes it dangerous is what has usually happened to it. Insulation blown or laid over it in an attic is the big one, because the system sheds heat into open air and burying it removes the cooling it was designed around. Extensions and splices added over the decades by whoever was handy, often without boxes. Over-fusing at a fuse box, where a 30 amp fuse replaced a 15 because the 15 kept blowing. Modern loads on circuits never intended for them. And simple age, where insulation has become brittle enough to fall away when disturbed.

The absence of a grounding conductor is a separate and permanent limitation. Without a ground there is no path for fault current and no protection for anything with a metal case, and no amount of care changes that.

So the honest framing is that knob and tube is not a fire waiting to happen, but it is a system with no margin left, and almost every house that still has it has also had decades of people doing things to it.

Will Insurers Cover a House With Knob and Tube Wiring?

Many will not, and this is where the practical pressure usually comes from rather than from anything a homeowner noticed themselves. Insurers treat knob and tube as an elevated risk, and carriers vary from refusing cover outright, to requiring replacement within a set period, to surcharging the policy, to asking no questions at all.

It surfaces at predictable moments. Buying a house, when the inspection finds it and the lender's insurance requirement collides with it. Switching carrier, when the new one asks a question the old one never did. Renewal, when a carrier updates its underwriting. Or after a claim, which is the worst time to discover the policy had a condition nobody read.

Because the pressure tends to arrive with a deadline attached, it is worth knowing where you stand before somebody else sets the timetable. An electrical safety inspection establishes what is actually present and how much of it, which is the information both an insurer and a buyer will want.

What an inspection often reveals is that there is less of it than feared. A house that was partly rewired decades ago may have a handful of original circuits left rather than a whole system, and the scope of work is correspondingly smaller.

Does Knob and Tube Wiring Have to Be Removed?

Removed is a stronger word than the situation usually requires. What matters is that it stops being live. The conductors themselves can be abandoned in place where they are genuinely inaccessible, and pulling every original wire out of a plastered wall would do far more damage to the house than leaving dead cable in it.

What has to happen is that every circuit still carrying current gets replaced with modern cable, properly grounded, landed in boxes, and protected appropriately. Once a circuit is dead and disconnected at both ends it is no longer a hazard and no longer an insurance problem.

The practical question is therefore scope rather than principle. How many circuits are still live, where do they run, and how much of the house has to be opened to replace them. A house with two remaining knob and tube circuits feeding upstairs lighting is a manageable job. A house that is entirely original throughout is a whole-house rewiring, and it usually comes with a panel and service upgrade attached, since a fuse box and original wiring tend to travel together.

Either way it is worth confirming what is actually live rather than assuming. Circuits that were abandoned in the 1970s are common, and a wire visible in an attic is not the same as a wire carrying current.

How Much of a House Has to Be Opened to Remove Knob and Tube?

Less than people fear, and the answer depends far more on the construction of the house than on the wiring in it. Rewiring is fishing cable through existing cavities wherever it can be done, and opening only where it cannot.

Attics and basements do most of the work, and New Hampshire housing stock is often helpful here. A house with a full accessible attic and an unfinished basement gives access to the top and bottom of most wall cavities, and a great deal can be run without opening a finished wall at all. Balloon-framed houses, which much of the pre-1930 stock is, have continuous wall cavities from basement to attic, and that makes fishing considerably easier than in later platform framing.

What forces opening is predictable: plaster and lath that will not take a fish tape, cavities with fire blocking, interior walls with no route from above or below, and anywhere a new box has to land. Where walls do have to be opened it is usually a series of small, patchable holes rather than sheets of drywall coming off.

The other thing that reduces disruption is timing. Rewiring during a remodel, when a kitchen or a bathroom is already stripped, is dramatically cheaper and less invasive than doing it as a standalone job. If a remodel or an addition is anywhere on the horizon, that is by a distance the cheapest moment to deal with old wiring.

How Much Does It Cost to Rewire a New Hampshire House?

A whole-house rewire on a 2,000 square foot house runs $18,000 to $20,000. That is the real working figure rather than a national average, and it covers replacing the branch circuits throughout, landing everything in boxes, proper grounding, and the panel work that goes with it.

What moves it is access more than anything else. A house with a usable attic and an open basement sits at the lower end. A house with finished space above and below, plaster walls, and awkward framing sits higher, because the labor is in the fishing rather than the cable. Size matters too, though not linearly, since a larger house has more circuits but the same fixed setup.

It is also rarely done all at once, and it does not have to be. Staging is normal and sensible: the circuits carrying the most load first, or floor by floor, or alongside work that is opening things up anyway. Kitchens and bathrooms are usually the priority because they combine the heaviest loads with the highest requirement for grounding and GFCI protection, which is also why a kitchen remodel is the single cheapest moment to deal with old wiring.

The counterweight is that this is a once-per-lifetime job on most houses. It is expensive and it is also the last time anyone has to think about it.

What Should You Do About Knob and Tube Wiring in a New Hampshire House?

Find out what is actually there before deciding anything, because the range of outcomes is wide and the assumption is usually wrong in one direction or the other. Some houses have far less live original wiring than the attic suggests. Others have circuits nobody knew were still energized, feeding a fixture in a ceiling that was plastered over decades ago.

If you are buying, get it established during the inspection period when it is still a negotiating point rather than afterwards when it is your problem. Our guide to what to check electrically when buying an older New Hampshire house covers the rest of what to look at.

If you already own the house, the trigger is usually either insurance or a project. Neither is a reason to panic and both are a reason to find out the scope, because a staged plan over a few years is a completely different financial proposition from an emergency full rewire with a deadline attached.

Knob and tube wiring is a New Hampshire reality rather than a rarity, particularly in the older stock around Manchester, Concord, Keene and the farmhouses of the Contoocook valley. We assess it, stage it, and replace it properly across southern and central New Hampshire, and we will tell you honestly how much of it is actually still live.