I have and old house and need to replace the Knob and Tube wiring in the walls (all other electrical has been replaced). Like most old homes, mine has randomly placed horizontal fire-stops (2x4s) between the studs with the old wires passing through them. If the walls were sheetrock I could find the fire-stops with a stud finder but my walls are plaster and I haven’t found a stud finder yet that will work. If I could find the fire-stops, I could cut holes fewer holes to run the new wire. I’m lousy at patching, painting and cleaning up dust so I want to do as little of that was possible.
Any helpful hints for finding these dreaded fire-stops? Or- does anyone know of a stud finder that will work with lath and plaster? My knuckles don’t have the experience needed.
Thanks in advance for your sage help.
Tony
Replies
Zircon has about five different models of stud finder. With the deep scan on the better ones, you can locate studs
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I've found that the best way to find a stud is to drill an oversized hole for a hollow anchor.
I do a lot of work in old houses with lath and plaster walls. Over the years, I have tried about 6 different stud finders, and I never found one that worked reliably.
The best means is tapping and drilling a few small holes. Next best is to use one of those super ceramic magnets, which you can (tediously) move over the walls, and the magnet will usually (but not always) pick up the nails used to attach the lath to the studs.
I assume you are not trying to remove the K&T wiring, right? If you are just fishing new romex, there are ways to do it with minimal damage to the walls.
********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
Use a snake to find the fire stop.
Open the outlet and pull out the box. Run the snake upwards until it stops. Mark where the edge of the box hole in the plaster is on the snake. Remove the snake, measure the distance from the mark to the end of the snake.
That is the distance the bottom of the firestop is above the top edge of the outlet hole.
If there are more than one firestop in each stud bay, you'll need to repeat the process from each opening you cut.
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
Or use a long flexible drill bit and go through the fire stop and the plate. Then attach the cable to the hole in the bit and pull it back.
That sounds like a fun gizmo to have. You have a photo or mfgs link for one of those?
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
don't know who makes them but I have seen my guys use'mthey look like a spade bit welded on the end of a 1/4 rod of spring steel.I know I have seen them in Home centers but I would bet any major electrical company would have them.I was reading thru with the intent of posting the wire snake idea and ya beat me to it.Good Job!!!!!!!Have ya put away the shorts yet? Saw my Bosch guys at a show couple weeks ago and pasted along the pictures and our thanks for supporting the Fest.Hope you are enjoying it---Mike" I reject your reality and substitute my own"
Adam Savage---Mythbusters
I was reading thru with the intent of posting the wire snake idea and ya beat me to it.
Good Job!!!!!!!
Heh, heh, heh.
Have ya put away the shorts yet?
I got out the shorts again this morning. For a while, it looked like I was gonna have to get out the woolies, but yesterday I was stripped to the waist doing lawn work and then jumped in the lake afterwards (which was distinctly refreshing, I must admit, but felt great for 3 minutes after drooling sweat for 4 hours). Might as well profit from the warm weather while it lasts....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
I think that others make them but here is a link to Greenlee's.http://www.lashen.com/vendors/Greenlee/hole_making.asphttps://www.jensentools.com/product/group.asp?parent_id=7210The local Lowes and I think HD has a limited selection.
Thanks. That looks like it goes on the wish list.
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
You said it Dino----we always use the fishtape method.
Growing up my was pops an electrical contractor, and I remember in high school helping him once on an old lathe and plaster house. We drilled a hole from the attic down through 3 stories using and extend a bit, then pulled the wire through.
That bit had to be 30 feet long..........hmm, I wonder if he still has it.
When in doubt, get a bigger hammer!
Edited 10/7/2005 8:06 pm ET by custombuilt
Edited 10/7/2005 8:07 pm ET by custombuilt
Hmmm ... There's probably an opportunity here for someone to develop a service where they use tiny cameras and a miniature version of one of those guided earth boring machines to fish wires through a structure.
DanH,
although it is now considered ...low tech..I used a small length of sash chain on the end of ####strong string...plus a ...flashlight with a small mirror to fish down walls...one guy could do it
it was something I learned in Chicago back in the 70's
...in a lot of the bungalows the fireblock was at 50""Edited 10/7/2005 3:11 pm ET by maddog3
Edited 10/7/2005 3:12 pm ET by maddog3
I don't figure trying to fish through blind-drilled holes in fire stops in this scenario; but knowing what height they're at will avoid having to punch a bunch of holes at mid-wall just to find it. Once the firestop is located only one or two small holes are needed and the wire can be fished through.
My favourite trick for trying to fish through a pair of blind holes--say a floor plate and a firestop, when installing a 3-way in a stairwell--is to shove a fish tape or piece of 12-ga wire down through one hole into the stud bay, and another one up through the hole in the lower plate. The ends of both fish tapes or wires have to have an open hook bent onto them, but it has to be narrow enough to pass through the holes you drilled in each direction without snagging.
Once you have the two hooked ends inside the wall, you and a partner wiggle the two tapes around inside the stud bay until you make contact, and then gently pull apart trying to get the two hooked ends to catch on each other. Sometimes it takes a while, but it works 90% of the time if you have enough patience.
Once you're 'hooked' you pull either up or down until you have a single length of fish tape or wire through both holes, and use that to fish back your NMD....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
i've done a similar method, just using a piece of 14 gauge wire, making a large loop and pushing it up into the wall, and hooking with a fishtape from above.
Amazing how many tricks my old electrician dad knows-----Guess I shoulda paid a little more attention, but at the time I had my mind on other things that learning building skills
When in doubt, get a bigger hammer!
First time I had to use that method, I re-invented it all by myself out of sheer necessity...because I'd forgotten to rough-in the 3-way in my own house's basement stairwell, duh, and I was not about to start busting holes in those nice smooth walls I'd just spent so much time taping and sanding and painting....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
Don't forget about the diagonal blocks that were used for anti-latteral movement stress regulators.
TRIGGER
Don't forget about the diagonal blocks that were used for anti-latteral movement stress regulators.
Sorry, but you've lost me there?
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
I think he was talking about the bracing on the smoke shifters.--------------
No electrons were harmed in the making of this post.
In the old days (pre-Long Beach earthquake), what they did instead of let-in 1x4 bracing was to run blocks in line on a diagonal. Think of taking the usual run of horizontal fire blocks, and rotating the whole line of them 40 or 50 degrees. They run all the way from sole plate to top plate. This isn't as strong as let-in, which isn't as strong as plywood shearwalling.
Lathers generally didn't put nails into the diagonal blocks, so the rare earth magnet that works so well for studs won't find them.
-- J.S.
Thanks, John. That's one I didn't know. Live and learn....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
I discovered one of those after the wall was beyond patching.
Shurly youv'e came across the diagonal blocks that are, I mean were, cut in to each bay, L to R or R to L , and prevent a wall to rack.
I'm pretty sure Milwakee has a complete line of these bits. At least I've seen a display at the tool store, and I think it was white with red writing. Anyway, it is a rack with a bunch of sizes of bits.
Take a cheap tapemeasure and remove the tip. Grind or file the end to a smooth rounded shape. Use this as your probe and you will have way to know how far up or down the block is. As a further refinement drill a hole near the end and you can use it to pull a string or wire too.
The best Zircon stud finders are pretty good but metal lath is mission impossible.
if you can get to "both" ends of the old knob/tube wiring, you should be able to pull fish tape or string using the old wiring and it should follow the path of the old wire through the stops - note the use of the word should - I have done this but also gotten to the point of getting out the long flex bit and going in through the existing outlet opening
good luck
You can always CAREFULLY pull the base trim along the walls you're doing wiring in and use the area behind the trim for much of your drilling work. If you're running wire from the basement up to another level, you'll have the challenge of finding fire stops but with the base trim off, you'll also have access to using the long flex bit to come down at the blocking if you pull the trim above the space you're working on as well. There's no real need to remove the old wiring as long as it's been disconnected at the panel. Good luck.
Edited 10/7/2005 10:44 am ET by Homewright