How to determine if lath or studs under drywall?

I live in a condo built in 1904 and I want to put up a heavy shelf. I know that some walls have lath behind them but I don’t know about this particular wall. What’s the best way to find out? I don’t mind drilling a small test hole because it will be hidden by the shelf.

Usually, a house of that age would have been built with laths covered with plaster. Then if it was remodeled later both laths and plaster would have been removed and replaced with drywall. In my experience it would be very unusual to put drywall over laths. Also, laths are too flimsy to count as extra support for hanging shelves off the wall.

In either case, if you are putting up a shelf you have the same two choices: find the studs and anchor the shelf supports to the studs with regular screws; or use drywall anchors to anchor the shelf supports to the drywall (with or without laths behind it). Be careful to choose the right drywall anchor based on how much weight you expect the shelf to carry - if the anchors can’t support the shelf it can pull off and leave huge holes in the wall that will need to be repaired. That’s why, if at all possible, it’s always better to anchor shelves and things directly to studs.

If you do have to use drywall anchors, always get beefier ones than you think you will possibly need.

The lath is nailed to studs. The trick is to determine if the wood behind your hole is lath, a bare stud, or lath over a stud.

Thumping the wall is how experienced folks tell the difference.

For others, get a stud finder and learn how to use it.

Then start thumping the wall - over the known stud vs 8" to the side. Try to remember the acoustic signature of the stud.

If it has modern wiring and plumbing, there is a good chance the walls are drywall - it is simpler to rip out the old and string wires and pipes as desired, then use drywall to cover.

Trying to match drywall to plaster can be tricky - I’ve done it,

I learned by attempting to pound a nail into a wall. When the hammer bounced off the nail and just about hit me in the head I knew I wasn’t dealing with drywall.

I would just assume plaster and lathe in a house built in 1904. Assuming it hasn’t been upgraded. You could mark your holes and try hammering a nail into the first spot. I bet you’ll be able to tell pretty quickly

Also, houses that old tend to have some gaps. See if you can look between the walls from the basement (between the walls) or down from the attic or even take some outlet or switch plates off. You might be able to see the plaster. Better yet, if you have any sliding doors, shine a flashlight into the pockets. If you have plaster and lathe you’ll see it in there.

Another thing, any cable outlets that are on both sides of a shared wall may very well not have a box. Pop one of those off and you’ll be able to see inside the wall.

One more, if you have central heating/cooling, looking inside your are returns. More often than not, those they just you stud bays.

Plaster and lath does not like nails - it will shatter and eventually crumble.
If you absolutely MUST use hammer and nails (pilot drill and screws preferred), at least put a bit of masking tape over the spot, the drive the nail through the tape - the tape will prevent/reduce the shatter.

Not so unusual in my experience. Which, admittedly isn’t very vast, but I can definitely confirm that is has happened at least once.
It would be better to rip out the laths and put the drywall on the studs, but my guess is that it was easier to just put the drywall right on top of them.

You could try playing drywall roulette. Tilt your head down and run into the wall head first. If it’s drywall on studs you only have a one in six chance of hitting a stud. If it’s plaster on lath you’ll find out on the first try. An astronaut and aircraft engineer explain here, starting at about 17:00.

It’s not impossible that there is drywall over plaster & lath – at some point in my house’s history, somebody installed thin sheets over drywall right on top of the existing plaster. I’ve also seen examples where the existing plaster was knocked off the wall, but most or all of the lath remains in place behind the drywall.

I second the advice to look in gaps. Electrical receptacles are good for this.

Thanks for the advice all! I appreciate you taking the time to answer.

Looking for gaps is a good idea. The wall on which I’m hanging the shelf hides a pocket door so I may be able to pull out the door a little bit and see behind it. This also means that I need to pay attention to the length of the screw/anchor that I use; I hadn’t thought about that so you may have saved me a big headache.

If I decide to purchase a stud finder does anybody have a recommendation on what options to look for? Or what brand?

For context, the shelf I want to hang is a variation of an “invisible shelf” like this one.

Actually, you might be better off pushing the door all the way in (so it’s open). It’s a lot easier to look through the cracks than it is to try to push your face against it.

(Ignoring all the notations on here), these are the cracks between the door and frame you can probably see through, especially if it’s an older house.

If you get a stud finder look for one that does deep sensing (1 1/2"), you will need this to find studs under lath and plaster. These will easily run you $40. If you are just dealing with drywall a basic $16 Zircon will work fine. Pick up some spackle, putty knife and sanding sponge while you are at it. Stud finders are tricky and many are duds. Knocking on the wall, driving a screw at your best guess and then moving over 3/4" until you find the stud is sometimes what ya gotta do. You’ve got some paint…right?

Another vote that your walls could be darn near anything. And there’s no reason to expect different walls to be built the same way. So don’t check one wall because it’s easy to check and assume all the others are the same construction.

If you have a pocket door and you’re intending to install the shelf so that it overlaps the area the pocket door retracts into, you’re almost certainly setting up for epic fail.

There is very little depth behind the inner surface of the wall and between there and the face of the pocket door. Like maybe 3/8" typically, and often less. There is almost always not enough depth for any through-wall anchor. You might luck out and have a very wide wall with lots of interior space. That’s certainly more likely in elderly construction than in modern construction. But odds are that’s not what you’ve got.

An expanding-plug anchor that remains wholly within the drywall / plaster / lath would work. But anything that sticks out behind the inner wall surface will not work. The bad news is the expanding-plug anchors have very light weight capacities.

I have this stud finder: It would find a stud under a layer of lathe, plaster and drywall.
I have also used a metal detector app. It finds the nails that are on the stud.

I’ve always found it easier to find studs behind lath using magnets instead of a stud finder. Two magnets clamping a thread in between them will stick to the column of nails holding the lath. Of course they’ll react to the nails holding up drywall too, but once you find the stud, you can find it again at any height with lath. Drywall is attached much wider.

The drywall should be nailed to the studs as well. Nailing to the lath is rather difficult as it will spring away from the nail

Just for the purposes of IDing the situation, I’d dim the lights. Then take a penlight and place it sideways against the wall and sweep the wall. The bumps from nails and such from drywall will be visible here and there.