Please help find studs in plaster walls

Hi, guys. A couple years ago I put up crown molding and picture rail molding in my home, which has plaster walls on 3/8" lath. (It's the original 90 year old plaster.)

Finding the studs was a chore, because the studs are often not at even intervals, and sometimes the lath has separated from the studs, so tapping with a mallet or probing with a nail doesn't work well. That electronic stud-finder gadget (I forget its name) was even less reliable.

Now I want to put up chair-rail and picture rail in another room, and I'm looking for a better way. I'm toying with the idea of using some sort of tool to cut through the plaster just deep enough to graze the studs. The groove would be hidden behind the molding, so I'm assuming I would not have to fill or patch it.

What problems would I have with that plan? What would be your tool of choice if you were to try it? Other suggestions on how to skin this cat?

Many thanks in advance.

Regards,

John

I'm not familiar with working with plaster walls at all, so take these comments with a grain, or 2,000, of salt. I think your idea of skimming to find the studs would work well. Mark your line, but I would use a jab saw so that it stops at the stud, you could mark it, go to the other side, and cut to the next one, and so on. Do you have a way to make sure there are no electrical lines running up and down in a wall cavity? Is the top of the wall in an attic where you could see if a wire is running down through the top plate? I wouldn't want to cut into one!! Do you need to fill back in the cuts? I don't know, but I'd think it would be a good idea to do so before installing the trim. If nothing else, it could help keep the two sections of wall from moving separately and creating other problems. So my guess would be plaster material, or something made for repairing cracks in plaster walls.
You might also make a "story board", maybe out of cloth or string that wouldn't shrink, and mark the stud locations on it for future use on the same wall.
Another place to search for answers would be the "This Old House" web site. They should have something on plaster repair if nothing on your specific questions. Jim.

Why cut the slot? Use a drill as a probe. Make a line where the chair rail will eventually go. Drill holes through the plaster along it. When you poke through the plaster+lath into air, that feels very different from poking through into a stud. Mark where you find studs. Use found studs to give you an estimate about where to find the next one.

A metal detector should work. It should find the nails that a holding the lath on.

Those super magnets will find drywall screws. The big ones will stick to the wall.

One problem you may run into, is that the lath may not run in exactly parallel lines, so that in the width of the chair rail from one wall to the next, you may find a gap to probe at one end, and not in the middle or at the other end.
Also, while it is possible that the stud spacing is uneven (I find this even in new homes where other tradesmen move studs slightly for their convenience) it could be the framers used a different spacing, which was fairly common back then.
Most tape measures will have a mark at 19 3/16", 38 3/8", etc.
The mark will be a small black diamond at the top of the tape blade at these measurements.

One other suggestion: instead of using the hammer to tap the wall, try using the heel of your hand. It makes a duller "thump" which is easier, at least for me, to hear the different sound where a stud might be.

I used the riubber coated end of my plumb hammer and then when I think I'm on I whack it with my knuckles closed fist and listen and feel.
Usually that get's me spot on but when I don't gee all too sure I take a power drill and a small bit and pierce a string of holes laterally out from the place where I think center is. Starting of course in the center.

As often as not that lets me locate a stud's sides telling me where the center of the stud is.
The holes can be filled with joint compound.

I've got plaster walls too, and finding studs is a pain.

The idea of cutting a slot seems like a bad one to me. Assuming you complete that without breaking chucks out (which is easy to do), you are left with the plaster having a loose edge which is just inviting chunks to fall off later (if you are going to do that, at least patch over the groove later with patching plaster). The vibration from a power saw can be pretty good at loosening the plaster from the lath on some plaster walls.

Use any and all methods available. For me, thumping with my hand is usually the most accurate. Most stud finders are terrible, but they may help reinforce other results. Take a concensus of whatever techniques you have to locate the highest-probability areas and then confirm using a drill. Once you get past the lath, there's no mistaking drilling into air versus into a stud. A series of tiny holes localized to where the stud seems to be is a lot less impact to the plaster and less to repair. Even thought the spacing isn't even, measuring usually gets you close enough to locate the next stud approximately with a little thumping.

I am curious to see how well a fish finder would work ...

I use a lumber wizard metal detector. It finds the nails used to hold on the lathe. Regardless of stud spacing, every piece of lathe was nailed at every stud. I think Zircon came out with a stud finer that is supposed to work on plaster walls due to its ability to sense metal, maybe this one: http://www.zircon.com/products/center_ms_i320.html

I haven't used that one so I can't say how it works.

I've seen one of the more expensive stud finders work well. Can't for the life of me remember the make of the danged thing... Most stud finders are crap.

Zircon! Thanks Peter.

That's a good idea. I'll have to see if my wizard detector works.

I have a Zircon detector (not the same one) that doesn't work at all. The cheap Sears detector I have from decades ago works much better, but is still not great on plaster.

(Of course, I have metal mesh lath not wood lath, which means i'm pretty much screwed on the metal detector thing. Density measurement is the only chance.)

If you have a foot panel on that wall then you can take a look at where the nails are located. Most likely they are where the studs are. You can also remove the foot panel and then poke there to find the studs.

Michael

When I was remodeling hotels we would use liquid nail and shoot nails in opposing angles(toe nail). With hotels having metal studs saved time and money without having to cut open walls and install backing.

+1 on using a drill. I do it all the time. I find stud centers to be from 14-18 OC all the time. Start at one side of an electrical outlet to find your first stud. Once you hit a stud drill to the left and then to the right to find the edges. Mark with pencil or painters tape above where the chair rail goes, move 16" and start drillin' again. Once finished, patch the holes..Easy!

PS. The plaster will trash the drill bit (1/8") in no time so plan on sharpening or replacing it.

construction adhesive and few brads.
take the easy way out.

using nails/hammer would damage or destroy the plaster keys.
VHB double sided tape is even better.


good luck.

I take a finish nailer, hold back the nose and shoot nails into the wall without touching the nose to the wall, maybe 3/4" away. The nails will go in flush until you come to a stud, and then they will stick out because the stud stopped them. There is your stud. You do it where you are going to cover it obviously, so there is no visible marks.

I have not found a stud finder that will work on lathe and plaster, I assume because of the density of the wall. This method takes a little getting used to but has worked for me for years. Nails are cheap. Time is not.

The other solution that I use ocasionally is to run a board with a complimentary profile around the room first that is heavily fastened, usually with screws, where it will be hidden by the crown/cove that is put on over it. That way I have a constant nailer just where I need it, and it adds a nice detail if done correctly.

+1 on using a drill with a small bit as a probe. Just be sure what you're hitting is a stud or corner bracing and not the wooden lath. You'll be able to "feel" when you hit a stud, or at least you'll see wood on the end of the drill bit. Much easier and less messy than a sawzall.

Jason

Quote:

---

Originally Posted by Jamie Buxton

Why cut the slot? Use a drill as a probe. Make a line where the chair rail will eventually go. Drill holes through the plaster along it. When you poke through the plaster+lath into air, that feels very different from poking through into a stud. Mark where you find studs. Use found studs to give you an estimate about where to find the next one.

---

I agree with using a small drill and "drill baby drill". I also find the nail gun method interesting althiough I think drilling is faster..

You mentioned the house is 90 years old. We refurbed our old house but tore off all the plaster/lathe so I can appreciate your comment that there seems to be no consistent spacing of studs. In our house I don't think there were any two the same. They ranged fron 12 inches to 36 inches. There was no plywood back then so uniform spacing didn't seem to matter. The other thing in our house was that the studs were full size 2x4, not the dressed studs of today.

My last house was plaster and lath, full 2x4 oak studs, 24" O.C. Offset from the studs 12" were 1x4 nailers (they weren't nailed to the top and bottom plates). I only discovered this because I gutted one room of the plaster and lath. Never again will I willingly own a plaster and lath house.

I did get a good Zircon stud finder that worked quite well--it had a "deep scan" mode that you activated by double-clicking the button, holding it down on the second click, then drag it across the wall as normal. It worked very well, ignoring the plaster and lath, and hitting all the studs. The only downside was that it would sense wires and plumbing in the deep-scan mode as well, so you had to pay attention to that possibility.

With modern stick-frame and drywall construction, I just knock on the wall with a knuckle in a very consistent manner. There is a slight sound difference when you knock over a stud versus a cavity. That, or I may remove a receptacle coverplate and probe next to it to find a stud and measure or knock from there. Sometimes even looking at the wall at a shallow angle I can find the drywall screws. Or, I carry a telescoping magnet in my pocket, and in a pinch, I can use it like a pendulum to hit on the drywall screws.

the base coat of that plaster is pushed through the lath so that it dries around and between it. that's the only thing holding the wall up. if you go knocking it loose in wholesale fashion by cutting the wall, you can have a wall go 'whomp' on you.

plaster isn't as delicate as drywall, but cutting and banging on it isn't really a good idea ;). as old and dry as it likely is it'll easily break loose in chunks if you do violent things to it.

If you have a metal detector http://ecx.images-amazon.com/images/...500_AA280_.jpgyou can use that instead of the stud finder to locate the nails used to attach the lathe to the studs. Once you get a reading, make a mark with a pencil or chalk and then work up and down from that mark you should be able to locate the stud then the rest should be on 16" centers from there.

My brother had a old house and you could see the ends of the studs in the basement as they used to balloon frame house. Stud went 2 stories and at the bottom they were nailed to the floor joist. Really old ones didn't even have fire stops. Old plaster is very fragile so don't tap too hard. If you do have a basement and can see the studs then find out where a outlet might be and measure the spacing from there. I always hated working on that old house. Try a magnet stud finder (something like this http://www.amazon.com/Stanley-47-400.../dp/B0000BYD3K), I had to use one at my brothers newer house, one of the previous owners put another layer of sheetrock and the stud finder was inacurate so I used the magnet one to verify the location.

I lived in a 1901 home for 12 years and replaced almost all of the junk trim with the nice Victorian stuff (that is a technical term). Here is what you need for your projects:

1. Liquid nails paneling and molding (LNP&M)
2. A brad gun for small trim
3. A Finnish gun for larger trim
4. Lite-weight Spackle (it has the consistency of whipped cream and dries hard like chalk) from HD ow Lowes - sold in the paint section (with liquid nails)
5. Caulking

First off, plaster walls will vary in thickness, a lot. All of your molding will need more holding power than your nails or brads will be able to provide (with or without the studs). Simply apply a a bead or two of the LNP&M and nail off your trim. The nails will provide the holding power while the LNP&M dries.

If you do not follow my instructions - I'll have an 'I told you so' waiting for you when your molding pulls away from the wall even though you spent 2 days locating all of the studs.:D

What about renting one of those thermal cameras... I'd bet the temperature delta between the studs and the studs is pretty abrupt. Never tried it, just trying to think outside the box.

Quote:

---

Originally Posted by Philip Rodriquez

I lived in a 1901 home for 12 years and replaced almost all of the junk trim with the nice Victorian stuff (that is a technical term). Here is what you need for your projects:

1. Liquid nails paneling and molding (LNP&M)
2. A brad gun for small trim
3. A Finnish gun for larger trim
4. Lite-weight Spackle (it has the consistency of whipped cream and dries hard like chalk) from HD ow Lowes - sold in the paint section (with liquid nails)
5. Caulking

First off, plaster walls will vary in thickness, a lot. All of your molding will need more holding power than your nails or brads will be able to provide (with or without the studs). Simply apply a a bead or two of the LNP&M and nail off your trim. The nails will provide the holding power while the LNP&M dries.

If you do not follow my instructions - I'll have an 'I told you so' waiting for you when your molding pulls away from the wall even though you spent 2 days locating all of the studs.:D

---

the alternative to this is trim head screws. they do have the holding power, but you are correct that the typical 15 guage finish nail shot from a gun they sell these days doesn't even come close to being able to hold large old moldings on the wall.

been there, done that, made the trip to the dump ;).

another alternative, which might be a good one when you cost estimate all of this work is...

1) do as much damage to the plaster as you need to as far as drilling and such goes, in the meantime live with the holes in the walls. don't be rough with it, but make holes where necessary and while you're at it, if you find any loose spots, drive a drywall screw in around those spots to tighten it up.

2) when you're done, and all of your trim is how you want it, hire a plasterer to come in and re-skim the walls.

the above is the "old way". they had no caulk centuries ago. the method for sealing the trim was the trim was put up over the base coat(s), and the finish coat was put up with the trim in place, so that the plasterer sealed the trim. this isn't really a major ordeal, any plasterer can skim the walls of a 3-4 thousand square foot house in a few days. therefore the bill won't be astronomically high, you're probably looking at few thousand bucks, maybe less depending on the size of the house. the benefit is it'll be done in an authentic way, if that means anything to you, and the 'dirty work' the plasterer will do, so you don't have to mess with it. all you'll have to do is prime and paint after he's gone.

this is the method i've taken with salvaging ruined trim in my house. i knock wallpaper and drywall loose with pretty much reckless abandon. if there are loose spots, i pull it up with screws to solidify it. the old dead skim coat my helper scrapes off with a big honkin siding scraper. then we put the trim back over the rough walls, and i have a plasterer come in and re-skim everything, and let him deal with the sealing and the leveling. once that's done it can all be finished/painted. last time i had my plasterers out here they did the entire upstairs of the house's ceilings, took them to lunch time over two days and cost me about 2200 bucks. considering i would've spent a month doing that work and another two months of back pain after, whereas they can even do a little dance on those stilts if you ask nice, it's money well spent.

I have a Zircon. It is supposed to be a stud finder. The problem with it is that a live electric circuit in the wall sets the damned thing off and it is useless. Save your money.

That's an easy one. Beat it repeatedly with a sledge-hammer until the plaster is completely removed. What's left would be the studs.

my suggestions is to look real close at the baseboards. most of the time the top nails in base board are nailed into the studs. just find the nails and level up and try a test nail. it has work for me on severl occasions

good luck

kendall

So many great ideas here, some of which I can use on this particular project, others I can use when I do the next room. Thanks, guys!

Regards,

John

Quote:

---

Originally Posted by William Falberg

That's an easy one. Beat it repeatedly with a sledge-hammer until the plaster is completely removed. What's left would be the studs.

---

blasphemer ;).

here's what i found in one my ceilings upstairs for a good example in this argument.

a 20 or 30 year leak. at some point a humidifier was put on the upstairs A/C, and it had been steadily dripping every few minutes for decades. after scraping the loose stuff and a new skim coat, and 4 coats of kilz to get rid of the stain, the plaster is fine.

what would drywall look like after a few years of water leaks? not that good, that's for sure...