Electrical on Old Houses

What is the typical house age for which rewiring is likely due to wire sheathing not to code? What is the typical cost to reroute new wiring by room for say a 3 Br 1200 sq. ft. house two story?


rewiring is really only necessary if the wiring has become damaged or if there is what is called “knob and tube” type wiring; this is where you have wiring that are held in place by ceramic stands-off. The insulation tends to be quite brittle. Most of the time when you find it, it has been taken out of service, but left in place. I have only seen it in houses built before 1930.

If its not broke, don’t fix it. aak5454 nailed the answer. If it had to be done it would depend on accessability. Cost of wire and fixtures are small when compared to cost of time on the job.

There’s something called “grandfathering” that applies to electrical work as well. Basically, this states that you won’t have to run out and update all your properties each time the code changes. It just means that any NEW electrical work done will have to comply with the NEW code. If the house was built in 1950, then the 1950 version of building code will apply to it, and unless there is a major problem then there’s no point in updating.

The only time updating becomes crucial is when you’re going from 60 amp fuses to 100 or 200 amp circuit breakers. Many home insurance companies will not even insure a property if it still has fuses.

Watch out for aluminum wiring too. :-\

There is nothing terribly wrong with Aluminum wiring itself, per se…it is actually bad connections/bonding that you need to be concerned with. I have had several properties with aluminum and, so far (knock on wood), there have been no problems.

Don’t be overly alarmed/concerned about aluminum wiring and it is certainly not a ‘deal breaker’…


I’ve got an old (1894) house (3500sqft) that still has the knob and tube type wiring and fuses. This summer we’ve been running two 'fridges, a deep freeze and three A/C’s with no problem but for safety sake I think its about time to update.

My question is what is entailed in updating this electrical system? Will they have to tear apart the walls to replace the wiring? Any idea on cost? Also wondering what I should ask or look out for when speaking to electricians. Thanks

As mentioned previously, all the old wiring will be left in place. Depending on construction method, I would think that one would not have to tear out walls. You will certainly want to add more receptacles - you probably have some halfway up a wall. So that will take some doing. Breaker boxes etc. as well. Our house was completely rewired from the knob and tube and fuses. It was scary until we had it done. Keep an eye on the contractor so that he doesn’t do it on the cheap - make sure he uses heavier gauge wiring and good quality switches. I have had to replace many of mine.

If you really want it done right, make sure the electrican pulls a permit and have the local building inspector do a rough and a finished inspection. Of course this method usually costs the most, but at least the town/city signs off on it.

I’m a little surprised you thought the electrican used a weaker gauge of wire. 15 amp circuits are on 14 gauge and 20 amp ciruits are on 12 gauge wire. What kind of wire was he trying to slip in? As for the switches, residential switches are the cheapest and they can be like 50 cents or less each. Commercial and industrial grade switches can go for $2-$5 each. So if you’re adding 10-20 switches, the price can soon add up to some serious money.