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We're planning on getting some updates to the electric wiring in our house. Installing more wall outlets, removing some knob & tube in the attic, installing GFCI outlets in required places, and generally getting things up to code (or closer to code).

The house is a 1925 bungalow, 1-story, with an unfinished attic and basement. Plaster walls. No plans to finish the basement at any point; it's used only for storage, work space, etc. All the wiring in the basement is easy to access - no ceiling. A bit less easy to access in the attic, due to insulation. Current wiring is a mix of knob & tube in the walls and attic (yes, possible fire hazard with the insulation), conduit and NM in the basement.

I realize that some of the wiring needs to run through the attic (we have 2 ceiling fans, 1 bath fan, and 2 overhead lights), but for the rest of it, can I have it all run in the basement, or as much as possible, and keep it out of the walls, except when directly underneath a switch/outlet/fixture? I'm not planning on doing the work myself, but I like the idea of being able to see it all, for maintenance and safety reasons, even if it means more linear feet of cable. That's a trade-off I'd be willing to make, if cost were the only factor.

Are there other factors to consider?

All the old knob & tube in the walls and attic would be disconnected and left in place.

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  • To clarify - I'm mostly asking about replacing the wiring that's in the walls. Or rather, leaving it in place, disconnecting it from all outlets/switches/fixtures, and replacing it with wiring that's entirely in the basement and attic except for runs directly up to and then immediately back down from the outlets/switches/fixtures. Maybe this is very common? I like that you know exactly where in the walls the live wires are (directly above and below any outlets/switches/fixtures), except for the one run of wire from the basement up to the attic to power the few ceiling fixtures we have.
    – PhilPDX
    Oct 11, 2015 at 19:13
  • Only shorter wires. But it much complicated, create the path through wall.
    – user263983
    Oct 1, 2021 at 19:21

3 Answers 3

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Doing the downstairs wiring in the basement is usually the way to go for the first floor, it's almost always easier to work in an unfinished basement than an attic.

If you can find someone that's experienced with homes with this older style of architecture everyone will be happier.

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  • Ground floor from basement, second floor from attic, usually.
    – keshlam
    Oct 11, 2015 at 0:14
  • Yes, don't worry, we'll definitely use someone referred to us by a neighbor. All the houses around here are about 100 years old.
    – PhilPDX
    Oct 11, 2015 at 19:14
  • What about the runs in the walls - say, from one outlet to the next, or from light switch to wall sconce? Any specific concerns in bedroom vs bathroom vs kitchen? Is my question at all clear? I've added a clarifying comment above. Sorry for my newbie-ness; I just want to get some ideas before talking to the electrician, so I'm not immediately agreeing to whatever he/she is proposing.
    – PhilPDX
    Oct 11, 2015 at 19:17
  • For your example of a sconce switch, you'd probably run one wire from the nearest junction box in the basement and up the wall to the sconce, then another from the sconce down the wall to the basement, over to where the switch is going to be, then back up the wall to the switch. Oct 11, 2015 at 20:37
  • For the overhead fixtures, one wire up to the attic might not cut it, because code and / or prctical requirements may dictate that they be on separate circuits. So a few wires up to the attic for overhead fixtures. If you are painting anyway, it might be simpler to just wire up from the basement. You'll may have to cut a hole in the wall up by the ceiling but it can be nice to keep the attic totally free of wiring. Oct 11, 2015 at 20:41
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Here is a perspective from a homeowner, not a professional electrician.

I love being able to work in the unfinished basement ceiling. Most jobs on the first floor (which is the only one you have) are much easier because I can very easily access in-wall spaces from underneath them and can very easily see the routing of existing cables. It's nice to be able to do installations and maintenance without usually having to damage walls and ceilings.

A major upgrade by a professional electrician might look different. It might be more economical for you to let the electrician run cables in a way that is most efficient from the perspective of someone doing a ton of wiring work all at once. It might make sense to damage and repair some walls and ceilings.

Depending on your house construction, the hollow innards of the exterior walls may be easier to access from the attic than from the basement. Maybe.

Knob and Tube

Even if not required by code I strongly suggest you remove all visible knob and tube because it can spook future buyers, inspectors, insurance assessors, etc. When they see it they don't know it's decommissioned.

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Leaving disconnected knob and tubing in the walls or ceilings does not really pose a major concern. The NEC requires all abandoned wires to be removed if they are accessible. For example during a renovation or in unfinished basements and attics. Mainly the area of concern is with drop-in ceiling grids where weight is a factor.

I would just remind you that certain types of service entrance wires are derated drastically when covered with insulation. For example, a #4/0 Aluminum SE 200 Amp service drops down to a 150 Amp just because it is covered with insulation.

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