How to Install Ceiling Laths?

Most ceiling problems start with poor installation. Skipping steps or using the wrong fasteners can lead to cracks, sags, or even total failure.

To install ceiling laths, follow a step-by-step approach with the right materials and spacing. The key is to ensure they are level, securely fastened, and evenly spaced.

Many people rush into ceiling work without understanding the details behind lath installation. Let me walk you through everything I’ve learned, so you can avoid costly mistakes and achieve a professional result.

How do you install laths?

Most ceilings fail because laths are poorly installed. Gaps, uneven spacing, or improper fastening ruin the whole structure.

To install laths¹, measure and mark joist positions, cut the laths to length, and nail them perpendicular to the ceiling joists with consistent spacing of 3/8 inch.

Tools and Materials You’ll Need

Begin by locating and marking your ceiling joists². Use a chalk line for accuracy. Then measure your lath strips so they span across several joists. If you’re using wooden laths, cut them with a hand saw. For metal laths, snips work better.

When placing the laths, start at one edge of the ceiling. Each piece should be nailed perpendicular to the joists, spaced about 3/8 inch apart to create a good mechanical key for the plaster. Always stagger the joints and avoid overlaps in one area.

Check that each lath sits flat. Any warping or unevenness will affect the final plaster finish. When done, give the surface a quick tug to confirm everything’s secure.

How to secure a lath and plaster ceiling?

Old plaster ceilings often sag or crack. That’s usually because the laths underneath weren’t fastened correctly or the nails have loosened over time.

To secure a lath and plaster ceiling, screw the laths back into the joists through the plaster using plaster washers³, reinforcing weak spots without removing the entire ceiling.

You don’t always need to tear down an old ceiling. If the plaster is mostly intact, you can secure it with screws and washers. This method works well for both repairs and reinforcement.

Step-by-Step: Repairing from Below

1. Identify sagging or cracked areas⁴.
2. Drill pilot holes through the plaster and into the lath underneath.
3. Use a plaster washer and screw to gently pull the plaster back against the lath.
4. Space screws about 4 to 6 inches apart across the weak section.

This method avoids full demolition and saves time. After all the washers are in, you can skim coat the surface for a fresh finish. It’s a good way to combine strength with appearance, especially for old buildings.

How do you secure metal lath?

Metal lath can be tricky to install. Without firm attachment to the framing, it can flex or pop, ruining your plaster finish.

To secure metal lath, fasten it directly to framing with corrosion-resistant screws and wide-head washers, ensuring the lath stays flush and tight to the structure.

Checklist for Metal Lath Installation

Start by unrolling the metal lath and positioning it across the ceiling. It should overlap by at least 1 inch where sheets meet. Always begin at one end and work across, checking alignment with each piece.

Use self-tapping screws⁵ and washers. These spread the pressure and prevent the mesh from tearing or bending. Place screws every 6 inches along studs or joists.

For corners or curved areas, cut and shape the lath with tin snips. Make sure it’s tight and conforms to the ceiling shape. A loose lath will lead to cracking and uneven plaster later.

How do you screw into a lath and plaster ceiling?

Screwing into this kind of ceiling without damaging it can be frustrating. Standard drywall anchors usually don’t hold and may crack the plaster.

To screw into a lath and plaster ceiling, locate a joist behind the plaster and drill a pilot hole before inserting the screw, using a stud finder or magnet to guide placement.

The plaster alone won’t hold heavy loads. You need to find the wooden laths or joists underneath. A magnetic stud finder⁶ works best, since it detects the nails used to secure the lath.

Once you’ve marked your spot, drill a small pilot hole⁷ first. This helps avoid cracking the brittle plaster. Use a wood screw for best results, and add a washer if needed to distribute the load.

If you’re hanging something light, like a smoke detector or hook, you can use a toggle bolt or molly anchor. But for heavier objects, always anchor into a joist.

Conclusion

Installing ceiling laths takes patience and precision. Done right, it forms a strong base for plaster that lasts for decades.