Quick Summary:
Finding studs in lath and plaster walls requires a specific approach. While magnetic stud finders work best by locating the nails, electronic stud finders can be tricky. This guide breaks down the most effective methods for locating structural support behind these older wall types, ensuring your projects are secure and successful.
Working on older homes often means encountering lath and plaster walls. These walls, made of thin wooden strips (lath) covered in plaster, present a unique challenge when you need to hang shelves, mount TVs, or make any kind of repair. Unlike modern drywall, lath and plaster is irregular and can be more brittle, making it hard to find the solid wood studs behind it. Many DIYers get frustrated trying to locate these hidden supports, worried about damaging the wall or having their mounted items fall. But don’t worry! With the right tools and techniques, you can confidently find structural studs in lath and plaster walls. We’ll walk you through the best methods, from simple tricks to more advanced tools, so you can tackle your projects with confidence.
Understanding Lath and Plaster Walls
Before we dive into finding studs, let’s take a moment to understand what lath and plaster walls are. These were the standard for interior walls before drywall became common. They consist of three main layers:
- Lath: Thin strips of wood, usually pine or cedar, spaced a short distance apart. These are nailed directly into the wall studs.
- Plaster: A mixture of gypsum or lime, sand, and water. It’s applied in multiple coats over the lath, creating a thick, durable surface. The plaster actually “keys” through the gaps in the lath, creating a strong bond.
- Studs: The vertical wooden beams that form the structural frame of the wall. These are what you need to find to securely mount anything heavy.
The irregular nature of lath, with its gaps and varying thickness, makes it harder for standard stud finders to work as they do on smooth drywall. The plaster layer itself can also be quite thick, adding another layer of difficulty. This combination requires a different strategy than what you might use for a typical home renovation.
Why Finding Studs in Lath and Plaster is Tricky
Several factors make finding studs in lath and plaster walls a bit more of an art than a science:
- Irregular Surface: The lath creates an uneven surface beneath the plaster, which can confuse some stud finders.
- Material Density: The plaster and lath can have varying densities, which might be misinterpreted by electronic sensors as wood or other materials.
- Nail Placement: While nails hold the lath to the studs, they are often not perfectly straight or consistently placed, especially in older construction.
- Wall Thickness: The total thickness of the plaster and lath can be greater than standard drywall, affecting how deeply a tool needs to sense.
- Lack of a Consistent Surface for Electronic Scanners: Many electronic stud finders rely on detecting changes in density across a smooth surface. Lath and plaster just isn’t smooth enough for reliable readings from many types.
This doesn’t mean it’s impossible. It just means we need to choose our tools and methods wisely.
Choosing the Right Stud Finder for Lath and Plaster
Not all stud finders are created equal, especially when it comes to lath and plaster. Here’s a breakdown of the types and which ones tend to perform best:
1. Magnetic Stud Finders (The Top Choice for Accuracy)
These are often the most reliable for lath and plaster walls. Instead of using electronic sensors, magnetic stud finders detect the small nails or screws that attach the lath to the wooden studs. These nails are typically made of ferrous metal (iron or steel).
How they work: You simply move the magnetic finder slowly across the wall. When it comes over a nail head, it will stick or pull noticeably. By finding several nails in a vertical line, you can pinpoint the location of the stud.
Pros:
- Highly accurate for lath and plaster.
- No batteries required.
- Simple to use – no calibration needed.
- Unaffected by wall density variations.
Cons:
- You must be able to see or feel the nail heads (or at least find where they are magnetically).
- May be harder to use on walls with a lot of metal mesh or screening instead of lath (though this is less common for pure lath and plaster).
- Requires a bit more looking around compared to an electronic scan.
Recommendation: For anyone dealing with lath and plaster, a good quality magnetic stud finder is a worthwhile investment. It’s often the cheapest and most effective solution.
2. Electronic Stud Finders (Use with Caution and Other Methods)
Electronic stud finders come in a few varieties, primarily center-finding and edge-finding. They work by emitting an electromagnetic field and detecting changes in density as they move across the wall surface. On drywall, they’re generally quite good at finding studs. However, on lath and plaster, their performance can be inconsistent.
Center-Finding vs. Edge-Finding on Lath and Plaster:
- Center-finding electronic stud finders aim to locate the exact center of the stud. These can be particularly unreliable on lath and plaster because the uneven surface and the lath itself can fool the sensors into thinking there’s a stud where there isn’t one, or miss the actual stud.
- Edge-finding models are a bit more forgiving. They detect the edges of changes in density, and by taking two edge readings and the space between them, you can infer the center. This might offer slightly more success but still requires careful interpretation.
Pros:
- Can potentially find studs faster if they work correctly.
- Some models have multiple modes for different wall types.
Cons:
- Often unreliable on lath and plaster walls.
- Requires battery power.
- Can give false positives or false negatives.
- Needs careful calibration and multiple passes.
Recommendation: If you already own an electronic stud finder, try it, but be prepared to use it in conjunction with other methods and to double-check its readings. Don’t solely rely on it for lath and plaster.
3. Radar/Stud Scanners (Advanced Options)
More advanced tools use radar or whole-wall imaging technology. These devices can often detect more than just studs, identifying pipes, wiring, and even different wall materials beneath the surface. They are typically more expensive.
Pros:
- Can detect items that magnetic and basic electronic stud finders miss.
- Provides a comprehensive view of what’s behind the wall.
- Can be very accurate once you learn how to interpret the readings.
Cons:
- Significantly more expensive than other types.
- Can have a learning curve for proper operation and interpretation.
- May be overkill for simple DIY tasks.
Recommendation: These are best suited for professionals or serious DIYers who frequently work with varied wall types and need to avoid damaging utilities. For most beginners to lath and plaster, magnetic finders are a more practical starting point.
Step-by-Step Guide: How to Find Studs in Lath and Plaster Walls
Now that we know the tools, let’s get to the process. Even with the “best” tool, technique is key. Here’s how to tackle it, focusing on the most reliable methods for lath and plaster.
Method 1: Using a Magnetic Stud Finder (Recommended)
This is your go-to method for lath and plaster.
- Gather Your Tools: You’ll need a magnetic stud finder, a pencil, and perhaps a small, sharp nail or awl for probing.
- Start at Known Points: If possible, look for areas where the wall has been repaired or where there might be an existing outlet or light switch. These are typically mounted to a stud. You can often see faint outlines or discoloration where previous items were mounted.
- Scan Slowly and Methodically: Hold the magnetic stud finder flat against the wall. Slowly slide it horizontally across the wall surface.
- Feel for the Pull: Pay close attention to the feel of the tool. It will “stick” or feel attracted to metal. On a lath and plaster wall, this attraction indicates you’ve found a nail head hidden within the plaster.
- Mark the Nail: Once you feel the magnetic pull, mark the spot with your pencil.
- Find Multiple Nails: Continue sliding the stud finder horizontally in the same general area. You are looking for two or three nails spaced typically 16 or 24 inches apart. Mark each spot where you feel the magnetic pull. The nails will be in a vertical line; the studs are the wooden supports behind them.
- Confirm the Stud Location: Once you’ve found a line of nails, the stud is directly behind them. You can usually estimate the center of the stud by looking at the gap between the outermost nails you found.
- Optional: Light Probing: If you’re unsure or to confirm the stud’s exact edges, you can carefully use a very thin, sharp nail or awl. Gently probe the wall surface in the suspected stud area. You’ll feel a distinct difference when you hit solid wood versus just plaster and lath. Be very gentle to avoid making large holes.
- Measure for Consistency: Measure the distance between the centers of the studs you’ve identified. In most homes, studs are placed 16 or 24 inches apart on center. If your findings align with this, it increases your confidence that you’ve found actual studs.
Method 2: Using a Low-Cost Electronic Stud Finder (With Great Care)
If you must use an electronic stud finder, follow these steps to maximize your chances.
- Read the Manual: Essential for any electronic tool. Understand its calibration process and how it indicates studs.
- Calibrate Correctly: Most electronic stud finders require calibration. Place the tool flat on an area of the wall you know does NOT have a stud (e.g., a large, open space between expected studs). Press and hold the calibration button for a few seconds until it signals completion. Crucially, do NOT calibrate over a stud.
- Scan Slowly and Steadily: Move the stud finder horizontally across the wall. Many requires you to press a button to scan. Keep the speed consistent and slow.
- Note All Indications: Make pencil marks on the wall every time the stud finder indicates something. Pay attention to lights, sounds, or on-screen readouts.
- Perform Multiple Passes: Do at least two scans horizontally in the same area, moving the tool from different directions (e.g., left-to-right, then right-to-left).
- Look for Consistent Readings: Hope for signs that appear in a similar vertical line for both passes.
- Confirm with Other Methods: This is where electronic finders on lath and plaster really need backup.
- Magnetic Finder: After getting suspect readings from your electronic finder, switch to a magnetic finder in that hot zone to see if you can detect nails.
- Light Probing: Use a thin nail or awl to gently probe the indicated areas. Feel for the solid wood of the stud.
- Visual Clues: Look for subtle lines in the plaster, areas of cracking, or old nail holes that might suggest the location of framing.
- Check for Outlets/Switches: Remember that electrical boxes are usually mounted to the side of a stud. If your electronic finder indicates a stud near an outlet, this can be a confirmation.
Important Note on Electronic Stud Finders: Many DIYers find that inexpensive electronic stud finders are often more frustrating than helpful on lath and plaster. They can be easily fooled by the plaster’s texture or the lath itself. If you’re having trouble, don’t hesitate to put it down and try another method.
Table: Stud Finder Comparison for Lath & Plaster
Here’s a quick comparison to help you decide:
| Stud Finder Type | Ease of Use (Lath & Plaster) | Accuracy (Lath & Plaster) | Cost | Best For |
|---|---|---|---|---|
| Magnetic | High | Very High | $10 – $30 | Beginners, anyone prioritizing reliability on L&P |
| Electronic (Basic) | Medium to Low | Low to Medium | $20 – $60 | Users willing to double-check with other methods |
| Radar/Scanner | Medium (with learning curve) | High | $100+ | Professionals, complex renovations, avoiding utilities |
Tips and Tricks for Success
Beyond the tools, smart techniques can make a big difference:
- Know Your Wall: If you’re lucky, you might see faint vertical lines in the plaster that indicate the location of the lath strips. The studs will be perpendicular to these.
- Listen to the Wall: Sometimes, tapping lightly on the wall can reveal a subtle difference in sound. A duller thud might indicate a stud behind the plaster, while a hollower sound suggests an empty space. This is an advanced technique and takes practice.
- Use Existing Penetrations: As mentioned, electrical outlets, light switches, and plumbing penetrations are almost always attached to framing members. If you need to hang something away from these, use them as reference points to estimate stud locations.
- Don’t Force It: If you’re drilling a pilot hole to test for a stud, start with minimal pressure. You should encounter resistance as you hit wood. If you drill through easily, you likely missed the stud.
- Best Practice: Invest in a Magnetic Finder: Seriously, if you plan to work in older homes, a magnetic stud finder will save you immense frustration and ensure a secure mount.
Safety First: What NOT to Do
When working with walls, safety is paramount. Here are some things to avoid:
- Drilling Blindly: Never just start drilling holes hoping to hit a stud. You risk creating unnecessary damage and, more importantly, hitting electrical wires or plumbing pipes.
- Over-Reliance on One Tool: Especially with electronic stud finders on lath and plaster, don’t assume the first reading is correct. Always verify.
- Ignoring Utility Scans: If you’re using a more advanced scanner, pay close attention to any warnings about electrical wiring or pipes. It’s always safer to know what’s behind the wall before you drill or cut. Organizations like the U.S. Consumer Product Safety Commission provide valuable home safety information, including risks associated with DIY projects.
- Using Too Much Force: When probing or drilling, use a gentle but firm touch. Forcing a drill can cause damage to the wall or your tool.
FAQ: Stud Finders and Lath & Plaster Walls
Q1: Are electronic stud finders useless on lath and plaster walls?
Not entirely, but they are significantly less reliable than on drywall. Their sensors are often fooled by the plaster’s texture and the lath beneath, leading to false readings. It’s best to use them with extreme caution and always verify their readings with other methods.
Q2: How do I know if I’ve found a stud versus just a nail in the lath?
With a magnetic stud finder, you’re directly locating the nails that attach the lath to the stud. You find multiple nails in a line. Then, the stud is located behind that line of nails. With an electronic finder, you must verify with a magnetic finder or by carefully probing to ensure it’s solid wood.
Q3: How thick is the plaster layer in a lath and plaster wall?
The thickness can vary significantly, but it’s typically between 1/2 inch to 1 inch thick, sometimes more. This is why depth detection on electronic stud finders can be problematic, and magnetic finders that detect nails are often more effective.
Q4: Can common household items help find studs in lath and plaster?
While not professional tools, you can try a strong magnet (like from a refrigerator magnet, though less sensitive) to feel for nails. A very thin nail or awl can be used for carefully probing suspected areas after you’ve identified a likely spot. Visual inspection for subtle lines or old nail holes
