How to Install Anchors in Lath and Plaster

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Lath-and-plaster walls need a different approach from drywall. The plaster face is hard but brittle, while the wood lath behind it is thin and can split or loosen. A conventional plastic drywall anchor may grip poorly, and driving a screw straight into the wall can crack the plaster. The reliable method is to drill slowly, identify what is behind the finish, and choose an anchor for the actual load.

Check the wall first

Before drilling, use a stud finder that can scan plaster walls, or check likely stud locations by measuring from a corner. Traditional studs are commonly spaced about 16 inches on center, but older framing varies. A strong magnet can help locate the nails holding lath to studs; confirm a line of nail hits rather than relying on one reading. Check both sides of the wall for switches, outlets, plumbing fixtures, and other clues to hidden wiring or pipes. If the location is uncertain, do not drill there.

For a heavy load, fastening into a stud is usually the best option. A screw into sound wood is generally more dependable than a hollow-wall anchor, and it avoids asking fragile plaster to carry the load. If you cannot reach framing, select an anchor rated for the wall material and the load—not just the weight printed on the box. Dynamic loads, such as a towel bar being pulled or a shelf bumped, need more margin than a picture hanging undisturbed.

Choose the right anchor

First determine whether there is a cavity behind the plaster and lath, or masonry directly behind it. A drill may pass through plaster and wood lath, then enter empty space; in some buildings it will meet brick or another solid backing. The right anchor depends on that result.

For a light picture or small hook, a nail into a stud or a suitably sized screw may be enough. For a moderate load in a hollow section, a toggle-style anchor is often a better choice than a standard plastic plug. Compare the required hole size and wall-thickness range before buying. A toggle cannot clamp securely if the cavity is too shallow, and it may not open if it hits framing or another obstruction.

If you need a set of general-purpose fasteners for a known hollow cavity, compare toggle bolts and wall anchors. For work where you have confirmed solid masonry behind the plaster, use anchors designed for masonry rather than assuming a drywall anchor will hold.

Tools and bit selection

Use a drill with a variable-speed trigger and a sharp bit. A cordless drill is enough for most pilot holes. A hammer drill is useful only when you need to drill into confirmed brick or concrete; its hammer action can shatter plaster, so keep it off while passing through the finish and lath. An impact driver is for driving screws, not for carefully drilling a brittle wall.

For wood lath, a sharp brad-point or standard twist bit makes a controlled hole. For plaster, a masonry bit can cut the hard surface, but use a regular drill setting and light pressure. A small drill-bit set covering roughly 1/8 to 1/2 inch is useful for pilots and anchor holes; match the final bit diameter to the anchor instructions. Do not substitute a larger bit because the hole feels tight—the anchor may spin or lose its grip.

Drill without breaking plaster

Mark the spot and place a small piece of painter’s tape over it to reduce surface chipping. Start at low speed with gentle pressure. Let the bit cut; leaning hard on it can crack the plaster around the hole. If the bit has a hammer setting, leave it disabled while going through the plaster and lath.

Drill only as deep as needed. You may feel the bit pass through the plaster, meet a thin layer of wood, then enter the cavity. Lath is commonly about 1/4 inch thick, though construction differs. If resistance suddenly disappears, stop and check the depth rather than pushing the bit far into the wall. If the hole is near a stud and you intend to use a wood screw, continue with a pilot sized for the screw’s core diameter, not its outside thread diameter.

Back the bit out occasionally to clear dust. If plaster crumbles, the hole grows larger than the bit, or a crack starts spreading from the opening, stop. Move the fastener location if possible. A loose, oversized hole is not fixed by forcing in a bigger plastic plug.

Install and test the anchor

For a toggle, make the opening to the specified diameter, feed the toggle through, and confirm that it opens behind the wall before tightening. Keep the screw aligned and tighten until the fixture is snug; overtightening can crush plaster or pull the toggle through the lath. For a masonry anchor, drill into the solid backing with the specified masonry bit, clear the dust, and install the anchor to its instructions. For a stud screw, use a pilot hole and stop when the fixture is secure rather than burying the head in the plaster.

Before hanging the full load, tug the mounted fixture gently in the direction it will be used. Any movement, cracking sound, or growing gap means the fastening is not secure. Remove it and reassess the backing, anchor size, or location. A toggle that spins, a plastic anchor that turns with the screw, and a screw that pulls out are all signs to stop—not to keep tightening.

If the item is heavy, valuable, or subject to repeated pulling, find a stud or use a mounting rail secured to multiple studs. The extra work is worthwhile: lath and plaster can be durable, but a brittle face and thin wood strips are poor places to gamble on an undersized anchor.