A big part of the reason I haven't blogged here since March is that around that time I took on the project of rewiring our 1920 house (replacing the old knob & tube wiring with modern nonmetallic cable that meets code), and it's consumed much of my spare time ever since. It looks like I'll finally finish the wiring part of the project later today, and then it'll just be a question of patching holes, etc. That's a big step, and I'm feeling good about it, and it's time to take a look back at what I learned from the experience, in case any of you are thinking of attempting the same thing!
When we first bought our house and tried to insure it, we found that the insurance company we wanted to use would not insure us because of the potential safety hazards of our knob & tube wiring. I got a bid from an electrician to rewire the house, but it seemed laughably high: US$7,000. (That's almost 10% the cost of the house.) It was clear from his attitude that he didn't want the job, so I figured the bid was inflated. Not so, it turns out. The materials don't cost much, but the labor is very intensive. I know I wouldn't take on another job like this for $7,000. At the time we didn't have that kind of cash on hand, but now that we do, if I had to do it again, I'd pay the electrician to have it done.
I told a couple of handy friends about the bid, and they offered to do the work for me if I'd do some work for them, and I accepted. Unfortunately their work wasn't ready to do right away, so I didn't do anything for them right away, and they stopped being motivated to do more for me. In retrospect I should have done something for them right away to keep them in my debt. Instead I got frustrated with their slow pace and decided to just do it myself... as if that would make it happen faster!
Nor is it brain surgery or other stereotypically difficult tasks. I watched my friends do their part of the wiring (including replacing the breaker panel, which required a permit from the city), and I read a chapter in a book (shown at right), and that was basically all I needed to know. There are about a dozen different parts involved, and half a dozen simple tools to learn to use, and a few simple concepts to internalize, but it's basically a one-person job, provided you've got the time. Time is really the limiting factor.
One of the most satisfying things about a project like this is that you can break it down into smaller and smaller projects until you have no excuse not to do the next step. For example, each circuit has maybe 10 branches, so you choose one to do first. A branch may go to a switch on its way to a fixture, so you do the switch first. That means cutting the old wire, removing the old switch, pulling out the two old wires, threading the two new cables, wiring the new switch, and cleaning up. Each of these tasks takes only a few minutes (5-60), and if you have to stop at any point, the worst consequence is that the light's out of service.
I will say that our house was a lot easier to rewire than some. For one thing, it's just one story, so every wire either went up to the unfinished attic or down to the unfinished basement; there were no wires in between floors. For another thing, essentially all the wall wiring was in interior walls, so I didn't have to work in the low part of the attic near the eaves. Finally, the building codes are a little less strict here than in larger cities. That's all I'm going to say about that.
Knob & tube wiring is called that because it's secured to the vertical studs with porcelain "knobs," and it passes through porcelain "tubes" when it goes through the horizontal joists. At least, that's the theory. If this were always the case, pulling the old wire out of a wall from the top or bottom (for example, between a lightswitch and the attic) would be next to impossible, and threading the new cable through the old holes would be completely impossible, because the new cable is wider than the old wire. That's what a clerk at Home Depot tried to tell me when, at the advice of the book pictured above (which you will note is published by Home Depot) I bought some pull string. He said he's rewired "thousands" of houses and never been able to use pull string because the old wire is too firmly attached (with knobs) and passes through openings that are too narrow for the cable (tubes). On top of that, the lath-and-plaster walls are full of chunks of concrete that squeezed through in the process of plastering the walls, and these chunks will get in the way of a cable, especially when you have to thread it from the top down instead of pulling it from the bottom up.
I told the clerk I'd take my chances with the pull string, and I'm glad I did. In all but one case, I did have to cut as many as three holes in the wall to get the cable through, and I removed the old wiring through these holes rather than from the top or bottom. But in several cases I was able to get the old wire loose from the knobs, remove the tubes (if any) and use the pull string to get the cable part or all of the way, and the very last switch I worked on last night, one wire was completely unsecured (no knobs at all), and I was able to pull the cable through without cutting any holes in the wall at all! I'm very glad I got the easy one last; if I'd done it first, I'd have had an unrealistic expectation of how easy the job would be. But I hear that even when I had to make three holes between the switch and the ceiling, I made less of a mess of things than a contractor would have done. Apparently the contractor approach is to just take out the whole section of wall.
Knob and tube wiring was conceived as a way to conserve wire when copper was expensive and labor was cheap. Electricians back then found all kinds of horrible shortcuts like splicing wires inside wall cavities. As people started adopting insulated cables instead, some people, including the previous owners of our house, decided it would be cool to use just one cable to go down to a switch and back instead of two: the power goes one way on the black wire and the other way on the white one. This is not a code violation, but the disadvantages of this method are that A) you'll be violating the color coding standard of the wires in the cable by using a neutral wire as a hot wire, creating confusion and a possible safety hazard for future owners, and B) you need to splice this nonstandardly powered cable into the rest of the circuit at a junction box (or at the light fixture -- won't the next owner will be surprised?), whereas if you'd done it properly and used two cables the splice would happen in the switch box.
For better or worse, copper is now cheap. Seriously, I spent less than $300 on the cabling for the whole house; that was not the expensive part of the project. Always use the color coding of the wires correctly, send two cables to a switch instead of one, and always leave yourself a few extra inches (like 6 or more) every time you cut a cable. Otherwise you'll find yourself moving a junction box a few inches over because the cable won't reach, and that is an awful feeling. You will hear posterity laughing at you.
I just mentioned the splices inside the wall cavities. Those splices were on a circuit that ran from the breaker box the full length of the attic, picking up half the light fixtures in the house, then down the far wall picking up the porch light and the outside outlet (where I sometimes plugged in heavy duty outdoor appliances), then all the way back through the basement picking up nearly half the outlets in the house as well. This was not a heavy gauge wire; it was 14 gauge. Two strands of 14 gauge wire with dozens of splices carried all that current, for years, without incident. Oh, and in the living room where I found all those splices, someone had decided to add a thin layer of drywall on top of the plaster, using not 3/4" drywall screws but 2 1/2" wood screws, penetrating deep into the wall, right where the splices were. Eek!
Lath is springy stuff. It's really very hard to drill or saw through, because when you push or pull on it it just bends. I found that I couldn't use an electric saw on it because the lath would just vibrate back and forth and not cut, so I used a hand saw called a "drywall saw" or "keyhole saw" (shown at right) instead. Actually I used three of them, because I wore the first two out! If you approach this wrong, you will sweat and strain and cuss. Here's the method I worked out that seemed to be most effective:
I've heard that I'm not the first to think of this, but it wasn't covered in the Home Depot book, so I'm going to mention it: twisting wires together prior to putting on wire nuts can be frustrating if the wires aren't held together tightly. It can be so frustrating that some people skip twisting the wires at all and just rely on the wire nut to hold the splice together. The Home Depot book says that's bad, but it doesn't say how to make twisting the wires easier. An easy way to keep the wires together is to simply tape them together with electrical tape (below the stripped end) before you attempt to twist them. Problem solved.
Loose-fill insulation, whether it's fiberglass or cellulose or vermiculite or whatever, has a tendency to flow into holes which makes digging holes in it very frustrating. There's a simple solution, which is to open up the top and bottom of a cardboard box so you have just the four sides, stick this down into the insulation, and dig the insulation out of the box. Remember to wear a good quality respirator when moving insulation of any kind.
I made a diagram of the wiring before I started and updated it as I went along, but in case that diagram ever gets lost, I know whoever lives here will have no trouble making a new one because I labeled every cable at every junction. I also made an effort to keep the attic wiring up out of the insulation as much as possible so that if we add more insulation, the wiring will still be visible. I want future owners of the house to look back and bless me for my thoughtfulness, not curse me for my laziness.
That's about it! If you've had a similar experience, I'd love to hear what you learned as well!