Mend a hole in your lath and plaster wall with these easy steps!

If you have lath and plaster walls that have been damaged in some way, such as having gaping holes in them as a result of electrical work, the following are some techniques that can be used to repair those walls. You will begin by fixing the lath, and then move on to patching the hole.

How Can a Hole in a Wall That Is Made of Lath and Plaster Be Repaired?

It is essential to make use of effective methods along with the appropriate materials when repairing lath and plaster. It is recommended to make use of a lime-based plaster that is softer and sets at a slower rate. One such plaster, which was developed for Big Wally's line of plaster-repair products, takes about an hour to set, does not have a tendency to crack or delaminate, and does not require sanding, which helps keep dust to a minimum. Do not use the so-called patching plaster that can be purchased at home improvement centers because it is significantly more durable than the wall's original plaster and it hardens in the blink of an eye.

If the lath is in good condition and the holes still need to be repaired, patching the lath is as simple as troweling on layers of mud. Plaster was typically applied on top of wood lath that was approximately half an inch apart over studs or ceiling joists up until the turn of the 20th century. Several coats were applied, the first of which was designed to fill in the gaps between the lath and create a solid foundation. The finish coats were applied after the base had been allowed to dry. It is a common practice to replace missing plaster with a piece of blue board, which is a wall board that is made to be coated with plaster. However, troweling on base coat is a faster method.

Six Easy Steps to Restoring Damaged Plaster and Lath

First, repair the lath.

Photo by Ben Stechschulte

Lath should be replaced if any lengths are missing, and all pieces should be refastened. Make sure to use drywall screws, and always drill pilot holes, to prevent the wood from splitting. Slip a piece of lath into the cavity and screw it to the back of the existing ones, parallel with the studs, if there isn't a stud to anchor a lath end. After that, you can use it as if it were a stud and screw new or loose lath to it.

2. Make the Wall's Fringe More Stable

Photo by Ben Stechschulte

Drill holes around the damaged area using a masonry bit measuring 3/16 of an inch, spacing them every 3 inches and leaving about 1 inch between each hole and the edge. Drill until the bit comes into contact with the lath. If it doesn't go through, make a note of it next to the hole. The holes should then be sprayed with plaster conditioner after being vacuumed. After 15 minutes, use a squirt of plaster adhesive to fill in any holes that were not previously marked. To remove any excess, use a damp rag to wipe it off.

3. Saturate the Substrate in Water

Photo by Ben Stechschulte

Wet plaster will have its moisture sucked out by dry lath and the edge of the plaster that is exposed before it has a chance to harden. To avoid this, make sure those areas are thoroughly covered in conditioner. Use a damp rag to clean up any drips or overspray that may have occurred. Before moving on to Step 4, you will need to ensure that the conditioner has had sufficient time to dry.

4. Apply the Scratch Coat to the surface.

Photo by Ben Stechschulte

Plaster Magic patching plaster should be mixed in a clean bucket with cool water from the tap until it reaches the consistency of natural peanut butter. Apply the mixture with a margin trowel up against the old plaster edge, as demonstrated, and all over the lath. Maintain a distance between this layer and the original plaster that is equal to half its thickness. Scratch the area with a scarifier to give it a rougher texture, and then scrape any blobs that are on the wall.

5. Apply the second coat with a trowel

Photo by Ben Stechschulte

After waiting for the scratch coat to become firm to the touch, which should take about an hour, you should then mix up a new batch of plaster to have a consistency that is slightly thinner and more similar to that of buttercream frosting. Employing a plastering trowel, level the mixture so that it is flush with the surface of the wall; then, remove any excess from the wall. Hold on for one more hour while I let that coat finish setting.

6. Give the Top Coat a Smooth Finish

Photo by Ben Stechschulte

Scrape the patch area until it is smooth using a taping knife that is 6 inches long, and then apply a thin layer of ready-mix joint compound over the patch. Allow to air dry overnight. After smoothing it out with a gentle scraper, apply a second coat. On the third day, apply a second coat, and once the first one has dried, smooth it out with a damp sponge in a gentle manner. The repair is now prepped and ready for priming and painting.

How to Repair Damaged Plaster Walls in the Event that the Lath Is Still in Good Condition

If the lath that is behind the old plaster is in good condition, then all that needs to be done to patch it is to trowel on layers of mud. The host of This Old House, Kevin O'Conner, walks you through the process of repairing holes in plaster walls in this video.

Patch Holes in Plaster in 7 Steps

1. Apply the base coat by pressing it into the lath. After all of the loose old plaster has been removed, apply a plaster base coat to the exposed lath using a flat trowel. Make sure to work the material into the spaces that are between the lath. Plaster that is applied in the spaces between the lath is referred to as "keys," and it serves to secure the material. Make sure to use a thick mixture so that it won't become sloppy before it sets. Strength is added to the base coat by the addition of nylon fibers during mixing.
2. Completely fill in the area so that it is flush. After the base coat has been keyed to the lath, fill in the area with additional base coat using a flat trowel. Once the base coat is flush with the surface of the old plaster that is still present, smooth it out very well with the trowel to reduce the amount of sanding that will be required.
3. Apply a bonding agent with paint. When the base coat is dry, apply a plaster bonding agent by brushing it over the base coat as well as the old plaster that is surrounding it. The bonding agent is essentially a glue that is based on water, and it ensures that there will be good adhesion between the old work and the new work.
4. Put tape on the seams. Apply a layer of nylon mesh tape over the seam that separates the new base coat and the old plaster. By taking this step, you will lessen the likelihood that any cracking that occurs in the base layers will telegraph through to the finished surface.
5. Cover the tape in wax. Applying a setting-type veneer plaster over the mesh tape and the surrounding wall with a taping knife and troweling a thin layer will achieve the desired effect. Plaster that is allowed to set quickly becomes rigid, which paves the way for the subsequent steps to be completed in a short amount of time.
6. Put on a finishing coat of joint compound. After the veneer plaster has had time to dry, use sandpaper to knock down any high spots, being careful not to sand all the way through to the mesh. Put on two coats of joint compound to finish the patch, making sure to let the first one dry before applying the second one and smoothing it out. The goal is to construct a surface that is sufficiently large so that it can be seamlessly integrated into the existing wall without producing an obviously elevated area.
7. The texture of sand When the second coat of joint compound has completely dried, use sandpaper with a grit of 220 to blend it with the existing plaster. First, you should concentrate on blending the patch's edges into the surrounding wall, and then you should smooth out the patch's center.

As was evident, replacing missing plaster involves following a process that is analogous to the one used during the initial installation. To make old walls look like new, first a base coat is applied, then several finish coats, and finally a light sanding is done.

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