Anchors for Lath and Plaster Walls: Stop Using the Wrong Ones!
You found the perfect spot for that new mirror. You grab your drill, a standard plastic drywall anchor, and confidently make a hole. But instead of a firm bite, the screw just spins, the anchor pulls out with a crumble of chalky dust, and your beautiful plaster wall now has an ugly, useless hole. This frustrating experience is all too common in homes with lath and plaster walls.
Standard drywall anchors are simply not designed for the unique construction of plaster. Understanding why they fail is the first step to hanging anything securely and avoiding damage. Unlike uniform drywall panels, these walls have a complex anatomy that makes them strong but brittle.
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Why Standard Anchors Are Doomed to Fail in Plaster
Lath and plaster walls are built in layers. First, thin horizontal wood strips called laths are nailed to the wall studs. Then, multiple coats of wet plaster are troweled over the laths, squeezing through the gaps and hardening into “keys” that lock the plaster in place. This creates a thick, durable, and sound-dampening surface.
This construction is precisely why plastic expansion anchors don’t work. They are designed to expand into the soft, consistent gypsum of drywall. In a plaster wall, they often hit a void between laths, encounter a hard wooden lath they can’t penetrate, or simply shatter the brittle plaster keys, leaving you with a loose anchor and a bigger problem.
The Anatomy of Failure: Drywall vs. Plaster
Imagine trying to use a tent stake in solid rock. That’s the essence of using a drywall anchor in plaster. The forces are all wrong. A drywall anchor needs uniform material to press against, while a lath and plaster wall is a composite of wood, plaster, and empty space.
Attempting to force a standard anchor can lead to spiderweb cracks, “popped” plaster, and an insecure fixture. To hang anything from a small picture frame to a large television, you need an anchor that is specifically designed to work with this old-world construction method.
The Best Anchors for Lath and Plaster Walls: Your Definitive Guide
The key to success is choosing an anchor that bypasses the brittle plaster and uses the structure behind it for support. This usually means gripping the back of the wall or securing directly into the sturdy wood lath. Here are the champions of the plaster wall world.
The Gold Standard: Toggle Bolts and Snaptoggles
For heavy-duty applications, nothing beats a toggle bolt. These anchors consist of a screw and a set of spring-loaded metal wings (the toggle). The wings are folded, pushed through a pre-drilled hole, and they spring open in the cavity behind the wall.
As you tighten the screw, the wings pull tight against the back of the wood lath or plaster, distributing the load over a wide area. This makes them incredibly strong and the top choice for heavy mirrors, shelving, and TV mounts. Modern versions called snaptoggles are even easier to use and provide a similarly robust hold.
The Versatile Workhorse: Molly Bolts (Hollow Wall Anchors)
Molly bolts are another excellent option for medium-to-heavy loads. A molly bolt is a metal sleeve with a screw inside. When inserted into a pilot hole, tightening the screw causes the sleeve to crumple and expand behind the wall, creating a secure grip.
One key advantage of a molly bolt is that the screw can be removed and reinserted without the anchor falling into the wall—a common frustration with traditional toggle bolts. This makes them ideal for items you might need to take down, like curtain rods or towel bars.
The Secret Weapon: Screwing Directly into Lath
Often, the best anchor is no anchor at all. The horizontal wood lath strips themselves are a fantastic mounting point for light to medium-weight objects. If you can locate a lath strip, you can often drive a simple wood screw directly into it for a surprisingly strong hold.
Finding the lath can be tricky, as electronic stud finders are often confused by the inconsistent density of plaster walls. A more reliable method is to use a magnetic stud finder to locate the tiny nails used to attach the lath to the vertical studs. Once you find a pattern of nails, you know you’ve found a solid mounting point.
Anchor Selection Guide: At a Glance
Choosing the right anchor depends on what you’re hanging and the condition of your walls. This table breaks down the best options.
| Anchor Type | Best For | Relative Weight Capacity | Pros | Cons |
|---|---|---|---|---|
| Toggle Bolt / Snaptoggle | Heavy items (TVs, large mirrors, heavy shelves) | Very High | Extremely strong; distributes weight effectively. | Requires a large hole; can’t remove screw without losing the toggle. |
| Molly Bolt | Medium-heavy items (towel bars, curtain rods, smaller shelves) | High | Strong hold; screw is removable; smaller hole than a toggle. | Can be difficult to set in very thick or brittle plaster. |
| Screw into Wood Lath | Light-medium items (pictures, clocks, light decor) | Medium | No special anchor needed; very small hole; surprisingly secure. | Requires locating the lath; not for very heavy loads. |
| Plastic Expansion Anchor | Drywall ONLY | Very Low (in plaster) | Easy to find. | Do not use in plaster. Will crumble plaster and fail. |
How to Install Anchors in Plaster: The No-Fail Method
Proper installation is just as critical as choosing the right anchor. Rushing the process is a surefire way to crack or crumble your plaster. Follow these steps for a perfect installation every time.
Step 1: Mark and Prepare the Surface
Once you’ve marked your spot, apply a small piece of painter’s tape over the mark. This simple trick does wonders to prevent the plaster surface from chipping and cracking as the drill bit begins to turn. It provides support to the plaster right at the entry point.
Step 2: Drill the Pilot Hole SLOWLY
This is the most critical step. Start with a drill bit much smaller than the final required size. Drill at a slow speed to score the surface first, then gradually increase speed and pressure. Once through the plaster, you may hit a wood lath—continue drilling steadily through it.
After the initial hole is made, switch to the bit size required by your anchor and enlarge the hole. This two-step drilling process minimizes stress on the plaster. For projects requiring many secure points, like when installing wainscoting on plaster walls, this technique is essential.
Step 3: Insert and Set the Anchor
Gently insert your chosen anchor into the hole. For a toggle bolt, pinch the wings and push them through until you hear a “snap” as they open behind the wall. For a molly bolt, tap it in gently until it’s flush, then turn the screw to expand the sleeve.
Be mindful of the total weight the plaster can support and ensure the anchor is set securely against the back of the lath, not just the plaster itself. Understanding the wall’s limits is crucial for safety.
Step 4: Mount Your Item
With the anchor securely in place, you can now drive the screw to hang your item. Tighten until it is snug, but do not overtighten. Overtightening can crush the plaster behind the anchor or damage the lath, compromising the hold.
Mistakes That Will Ruin Your Plaster Walls
Avoiding common pitfalls is key to success. The biggest mistake is treating lath and plaster like drywall by using plastic anchors. These will almost always fail and damage the wall.
Another frequent error is drilling too quickly or with a dull bit. This creates excessive vibration that can crack the plaster. Always use a sharp bit, start slow, and let the drill do the work. Finally, never guess where a stud or lath might be. Taking a few extra minutes to locate a solid piece of wood will save you from a major headache later on. The integrity of your walls is just as important as the project itself, a principle that applies to everything from hanging a shelf to a major home rewiring project.
Frequently Asked Questions
What are the best anchors to use for lath and plaster walls?
Metal toggle bolts or molly bolts are highly recommended for lath and plaster walls. These types of anchors expand behind the lath, distributing the weight over a larger area for a secure hold. Standard plastic wall anchors are generally not effective as they can have difficulty penetrating the wood lath and may not expand correctly.
Can I hang heavy items on a lath and plaster wall?
Yes, you can hang heavy items like shelves, mirrors, or televisions on lath and plaster walls. For the most secure hold, it’s best to anchor directly into a wall stud. If a stud is not available in the desired location, heavy-duty toggle bolts or molly bolts are a reliable alternative for supporting significant weight.
Why don’t standard drywall anchors work in lath and plaster?
Standard plastic drywall anchors are often ineffective in lath and plaster because they are designed for softer, hollow drywall. They can struggle to pierce the wooden lath strips behind the plaster and may not expand properly, leading to a weak or failed anchor point. The plaster itself can also be brittle and crumble if the wrong type of anchor is used.
Do I need to drill a pilot hole for anchors in lath and plaster?
Yes, drilling a pilot hole is a crucial step when installing anchors in lath and plaster. It is recommended to use a masonry bit to drill through the plaster layer. This helps to create a clean opening and prevents the plaster from cracking or crumbling during the anchor installation.
What is the difference between a toggle bolt and a molly bolt?
A toggle bolt has spring-loaded “wings” that fold to go through the hole and then open up behind the lath. A molly bolt is a sleeve-type anchor that expands and grips the back of the wall as you tighten the screw. Both are effective options for lath and plaster, with toggle bolts often cited for heavier applications.
