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Electrical Pitfalls of an Old House

Image Credit: Scott Sidler

If the picture of this breaker box doesn’t scare the pants off you, then you are one crazy, living on the edge kinda person. It doesn’t take a professional to know that this is not a well designed electrical system.

My wife and I are finally turning our unfinished attic into a kid’s bedroom this year to make room for our growing family (our 2nd boy was just born!). I’ll be doing a few posts on the process soon to give you the inside scoop on the project.

For the attic, we needed to have new lines run to the upstairs, so I called in my favorite electrician to do the work for me. Steele of WALSTIB Electric does most of my electrical work in Orlando because he knows old houses so well. And with a name like Steele, how can you go wrong?

I know old houses well enough to know that I don’t want to take any chances messing with the rat’s nest of wires in this place myself. There’s a time to call a pro and for me, this is the time.

While he was here, I got to thinking, “What a great post it would make to ask him about the biggest dangers he finds when it comes to electrical systems in old houses.”

So, today I’m going to let you pick the brain of a professional electrician who often works in old houses.

Here are his answers to four of my biggest questions about old electrical systems.


Why is knob & tube wiring so dangerous?

Knob & tube wiring was one of the first forms of electricity in houses. For its time, the system was ingenious and simple. It was incredibly safe initially, but has some shortfalls that are exacerbated by old age.

Problem #1: Knob and tube connections were soldered and taped so they were very strong, but they were not done in a junction box. So, if one of these connections should happen to fail, it creates a definite fire hazard since it is exposed.

Problem #2: The insulation used on knob and tube wiring was rubber, which becomes very brittle with age and eventually crumbles off. This missing insulation means that there can be exposed live wires in walls and attics, which is never good.

With many old houses without insulation, this wasn’t as big of a fire hazard as it is today when homeowners unknowingly install blown-in insulation over active knob & tube wiring creating a very big fire risk.

Solution: If you suspect your house has any knob & tube wiring, have a licensed electrician determine if it is still active and replace it as soon as possible.


What is the most common safety issue with electrical systems you come across in old houses?

I’d have to say that would be all the patches and splices that inevitably occur over time. What was initially a well thought out electrical plan becomes a mess of wires from different generations of additions and changes to the electrical needs of the occupants.

I see lots of hidden junction boxes which is a big No No. Also, way too much use of electrical tape to patch things up. Electrical tape is not a permanent solution to an electrical problem, but a lot of homeowners and handymen use it that way.

Another big problem is overloaded circuits. Adding one new outlet to a circuit doesn’t usually cause a problem, but adding four over the course of 40 years will cause an overloaded circuit due to today’s higher electrical demands.


What’s the story on aluminum wiring? Is it really a problem?

Aluminum wiring became a popular alternative in the 1960s and 1970s due to skyrocketing copper prices. The problem with aluminum wiring isn’t actually the wiring- it is an issue of connecting dissimilar metals and the results can cause arcs and fires.

Here’s the typical scenario:

A homeowner or electrician adds new receptacles or switches to the house. Standard receptacles have brass screws which are a copper alloy, so they work fine in most houses, but with aluminum wiring, you need specialized electrical components that have aluminum fittings.

Most folks wouldn’t think about this and so they will install the standard receptacles which will cause galvanic corrosion and eventually lead to an arc and possible fire.

Solution: Investigate whether your house has aluminum wiring and make sure anything that connects to the wiring is made of aluminum, NOT brass or copper.


What can a homeowner best do to protect themselves when buying an old home with old wiring?

The best thing you can do is have a thorough inspection by an electrician you trust. They will be able to point out potential issues, though there is no way to tell exactly what is hiding behind the walls.

They will be able to make suggestions based on their experience to help you have as safe a house as possible.

I hope you learned as much as I did from my interview with Steele. I always think that the biggest fears we have regarding old houses lie in the unknown. The more we know, the less we worry about things.

So, take this opportunity to do a little detective work on your house or get your electrical system checked out by a pro so you know what you’re dealing with.


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13 thoughts on “Electrical Pitfalls of an Old House

  1. Thanks for an informative article. Now I’m officially scared s***less lol!. We have knob n tube in our old Massachusetts house. This will make the house difficult to sell, if possible at all. Some of the wiring was replaced when we renovated parts of the house, but I suspect there is still a substantial amount remaining if the basement is any indication. The house was built around 1920. The cost of removing it in a 2&1/2 story home scares me so much that I avoid getting an estimate. We did replace the old fuse box with circuit breakers and added a second panel on the third floor to handle heavier load, for air conditioners for example. We do get fluctuations in electric flow, like lights dimming, when the draw is heavy. The house is not insulated but all new windows were added. I noticed bees around the fountain along with two small perfect round holes in shingles above the third floor dormer. They have been there forever. I get anxious about bees in the wall with exposed wiring. I love our house but am not in financial shape to invest in a big job right now. Is rewiring something that could be down over time or does it have t be do e all at once? Any idea of cost involved, roughly? my husband is handy so he can do all repairs afterwards. Thanks so much!

    1. Costs will vary based on region and square footage of home, but I suspect your looking at $10-$15k to update the wiring in your home. I’m not an electrician, but have gotten plenty of estimates and had electricians rewire a few of my houses in the past.

  2. So our 1929 bungalow-ish has some of this and some of that and knob and tube. As we did the work ourselves we got MANY bits of advice here and there. When it came to the attic space with knob and tube, we ended up boxing in the wiring so that no insulation would get to it. I can’t remember why we went that way instead of replacing it at the time, but that was 13 years ago and MANY projects ago. What do you think? Time to break through the wall again…? 🙁

  3. Thank you for the information.We recently got all knob and tube wiring replaced by the shock doctors.The knob and tube wiring gets dangerous if it is more than 70 years old ,the porcelain knobs and tubes may crack or break, old wires sag and fray, and the sheathing turns brittle and falls off, exposing the live wires.Knob and tube wiring is designed to be strung through open air so the heat can dissipate well. Improved insulation techniques create hazards as loose-fill insulation blown into the attics and walls of older houses will come into contact with the wires creating a serious fire hazard.

  4. Does anyone have experience with any web sites to help maintain your home? I’ve started my own Excel spreadsheet to help with the process but it seems like there should be a better way. I found a couple web sites that seem to offer some help and wondered if anyone knows of others. The two I found are http://homeshape.com and . I signed up for them both but I’m not sure which one to put my energy into because I have to add all my appliances and other things that need some sort of maintenance and that will take a little time. It looks like HomeShape offers the most help and actually locates owner’s manuals and other repair and maintenance information for you including a calendar where they schedule things like haz waste and yard collection dates.

  5. Is it possible to replace the wiring without destroying the plaster and original baseboards? Our knob and tube outlets are in the baseboards, and for walls with switches, they are plaster.

    1. Rhonda, there will almost always be SOME damage to the plaster when rewiring. Just make sure your electrician knows you want to keeps things as clean as possible. The amount of damage depends on how much your electrician cares about your house.

  6. Great to hear that you are converting your attic. That is exactly my next project in my 1910 house. I already have utilities roughed in but insulating and ventilation are big questions I am trouble grasping. Looking forward to seeing your updates!

  7. This is great information and timely. I have to update the electrical in my 1895 house. Thank you for the tips !!

  8. When we moved into our 93-year-old house, there was a variety of electrical wiring from over the years, all in different stages of use. We hired an electrician to sort it all out and put in a proper electrical box, and he also upgraded our amps from 100 to 200. It cost a few thousand dollars, but it’s one of those investments that’s totally worth it from a safety standpoint. Old houses are wonderful, but they do need a few important upgrades like this. Thanks for these tips!

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