Anybody re wired an old house from knob and tube to romex,to me it looks just about impossible without bashing the walls down.Being a commercial electrician i have no experience doing this and i know in my area there is lots of this work.Talking to various trades they tell me the electricians accomplish this feat of magic with little damage to the walls.Are they telling me the truth?Any tips?

I would minimize the damage by fishing the rope independently of the K&T, abandoning the K&T in the walls, and removing every inch of it that was exposed. I would also re-use the bored holes where I could, one rope to a hole.

Don't believe the other trades, there is always a lot of patch work to be done.

Minimize it by cutting your holes behind the baseboard when you can, and re-using the receptacles and switch openings when you can.

personally, i try to open up in the baseboards to pull up into walls, and do as much from the basement up onto the main floor, then send all the upstairs runs up thru one or two stud bays to keep cutting and patching to a minimum, also old work boxes are a godsend, especially those smartboxes advertized here....oh yea dont forget a good sawzall

I have done several rewires of this type and they can be very time consuming. As far as damage to finish--sometimes you have to, but it usually can be avoided. Also we use the old K & T going down to the recepticles as pull wires for the new romex with pretty good luck. The switches are usually a different situation--they mostly had the insullators inside the wall and we drop down chains or rope to pull them in. Be careful when demoing out the old K & T and don't take out more than you can install in a day because it can be difficult to figure out which wire goes where at the end of the day if you need to temporary these circuits for the night. Good Luck.

Justin

The secret to this is to "know your framing style"! Depending on the age and style of the building. Where I'm at we have three basic types of framing:

Balloon = 1850's - 1900 Vic's and Ed's
Plated = 1900's - present All styles
Remodeled to death = Who knows what's in there!

Some good tools to have:
A roto zip with plaster blades and wood blades. (remember to have lots of them and use the right blade for the material, or you'll burn them out too fast.)

Fishing poles The glow in the dark kind are the best

An inspection mirror, and a fiber optic flash light that can bend inside a hole.

But as for abandoning the K&T, you are supposed to remove it now!

But remember to tell your customer that sheet rock is a lot cheaper than your time!
(But wood work is not...)

I have done a fair amount of K & T rewires. On some historic homes the owners will not want any damage to the plaster. I use the fish rods, the flex bits with extensions, mirrors and lights. I've never had the luck of balloon framing, it's always plated with a double plate of full cut two by fours, four inches total. That's where I use the auger bits with a short extension in the Milwaukee.
If theres bracing in the center of the wall then you need the flex bits, masonary type since there is always a pile of plaster on top of the brace. I usually don't run into the wall bracing, but it does make the job A LOT more costly.
One more thing, a lot of homes built at the turn of the century had no receptacles, only ceiling fixtures. The receptacles were added later usually using loose K & T (no knobs inside the wall) and later using armored cable. This makes it easy as you can use these wires for your pull wires. On the AC just remove the box and the connector (it won't fit thru the bored hole) then hook on and pull away.
Then the crawl space or basement is a good place for the 1st floor wiring. We have very few basements in Arizona and I hate crawlspaces, I usually do it all from the attic.
Oh and spend a good long time on your estimate. Check for wall bracing, check for previous additions that you can use for pulls etc. You don't want any surprises. I always draw a complete map of the old system first, then take that home and draw up your new circuits. Customers are always surprised and impressed that you would spend so much time on their bid rather than just looking up in the scuttle hole and shooting them a price from the hip.

Oh forgot blocks and bracing.....

Except for balloon older 1900 - 1950 will have diagonal bracing at every corner. Top from the corner out to the floor. A good area to avoid.

And not sure when they started 48" fire blocks. But guaranteed for remodels if the walls got opened. Around here they were still doing K&T up to the mid seventies for some reason. I never liked those flex bits, and prefer, infact insist on opening the wall to drill if I can't get it from above or below.

Oh... for S&G I googled "Knob And Tube"...
This is funny!

http://www.dimensional.com/~jbettin/mess/knights.htm

thanks for the tips.Now i,m just going to assume that on the second floor of a house that there is no way to avoid damage to the walls of devices on perimeter walls because of the grade of the roof and no access from the attic because of the grade as well as the same can be said if their is no basement for devices on the main floor.(these seem to be t + m jobs but as you know, homeowners hate this).

Are you thinking about taking on a job like this?

[This message has been edited by Electricmanscott (edited 08-24-2004).]

I am looking at it as a [possibility,as i have been asked to price this type of work in the past.Typically a 3 bedroom house I,m guessing would be about a week for two guys?

The last K&T rework I did I was able (with the help of a Stanley mini-prybar, a flashlight, and an inspection mirror) to pop the knobs off the studs and use the old linen covered wire as a pulling means.

WATCH OUT FOR "HIDDEN" TUBES" (usually under debris in the stud space. Depending on the direction they were driven they can either "pop" up towards you, or they have to be broken out. There were several that were "doubled up" on penetrations @ floor level (1/2 of a tube capped by a regular tube... P.I.T.A) that were heck to remove.