How To Patch Plaster Walls

worker plastering gypsum board wall
Table of Contents
    Add a header to begin generating the table of contents

    Plaster walls lend an air of sophistication and allure to any room, but with the passage of time, they can get damaged with cracks, dents, or even holes. 

    Thankfully, plaster walls may be easily patched and restored as long as the appropriate tools and procedures are used. 

    In this tutorial, we are going to take you step by step through the process of patching plaster walls, beginning with the preparation stage and ending with the final touches. 

    This guide will provide you with the knowledge and skills you need to undertake this project with self-assurance, regardless of whether you are an experienced do-it-yourself enthusiast or a new homeowner.

    What is Plaster?

    Plaster is an almost magical building material that can be used to make and cover walls and ceilings when applied with the appropriate amount of creativity and skill. 

    Plaster was traditionally made by combining dry ingredients such as sand, lime, and bovine hair (or straw or dung) with water to produce a wet, flexible medium that cures and hardens as it dries. 

    Around 150 years ago, a new component called gypsum was added to the mixture of sand and lime to accelerate the plaster's curing time and make it possible to work with the mixture more quickly.

    What is a 3-Coat Plaster System?

    Lath, which can be made of thin wood slats or metal mesh, is used as a foundation in classic multi-coat plaster systems. 

    This lath is then linked to the framing of the wall. 

    On top of the lath, three layers of wet plaster are placed in the following order: the scratch coat, the brown coat, and the finish coat.

    The Coat With Scratches

    It doesn't take long to apply the scratch coat. To create "keys" that will harden and lock the coat in place as it cures, the plasterer will force the wet mixture through the holes in the lath in a thicker-than-normal manner. 

    After that, the top surface of this scratch coat is scored to prepare it for the brown coat, which is the second coat.

    The Overcoat in Brown

    While the brown coat is applied, the plasterer will smooth out the wall surfaces and ensure the corners are square and plumb.

    The Top Coat (Finish Coat)

    After the brown coat has had enough time to harden, the top coat, also known as the finish coat, is applied. This coat might have a smooth finish or one of several textured finishes. 

    The end product is a handcrafted wall surface that is of the highest quality and boasts astonishing soundproofing and insulating capabilities. This article discusses three-coat plaster, which is troweled smooth after being put to wood or metal lath and then allowed to dry. 

    Moldings, on the other hand, are formed in place by running a template across wet plaster in order to generate the desired contour. 

    Cast in a mold, then put to the surface, ornaments such as ceiling medallions are one example. 

    The same result can be achieved by recreating older work, but that's a different tale.

    What is Drywall?

    Drywall is a uniform panel of gypsum plaster that is squeezed between thick sheets of paper and is known by a variety of other names, including plasterboard, gypsum board, rock, wallboard, and Sheetrock (a trade name). 

    Drywall has a remarkably extensive history, with the earliest varieties reaching back to the late 19th century. 

    Although it is not as old as plaster, it has a significant history nonetheless. 

    Between the years 1910 and 1930, it started its unstoppable advance up home walls and ceilings in the United States.

    Drywall comes in a standard size of 4' x 8' and can have thicknesses ranging from 1/4" to 5/8", making it a very simple material to install across big areas, particularly when compared to plaster. 

    It is possible to nail or screw it to studs made of wood or metal. 

    After the joints in the drywall have been coated with joint compound and taped, the drywall is ready to be painted or covered with wallpaper.

    Manufacturers produce drywall for a wide variety of applications and environments. 

    For instance, there are various drywall resistant to fire, moisture, or mold, and rock can be used as a platform for installing tiles. 

    Because of this, it is now much simpler to adapt drywall with particular qualities to regions where there is a problem with mold or moisture. 

    Greenboard is a wonderful option for use in a bathroom, particularly one in which the old plaster has long since been removed or is in poor condition due to, for example, water damage.

    How Do You Repair a Hole in Lath and Plaster Walls?

    closeup hand worker plastering cement wall building house (1)

    It is essential to use effective methods and 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 designed for Big Wally's range of plaster-repair products, takes approximately an hour to set, does not have a propensity for cracking or delaminating, and does not require sanding, hence reducing the amount of dust produced.

    Do not use the so-called patching plaster that can be purchased at home improvement centers since it is significantly more durable than the wall's original plaster and hardens in the blink of an eye.

    If the lath is in good shape and holes need to be repaired, patching is as simple as troweling on layers of mud with a trowel. 

    Plaster was often put on top of wood lath that had been spaced approximately half an inch apart over studs or ceiling joists up to the 20th century. 

    After applying several coats, the first was designed to fill in the gaps between the lath to create a solid foundation. The finish coats were applied after the base had been allowed to dry. 

    It is typical to replace missing plaster with a piece of blue board, a wallboard meant to be coated with plaster. 

    However, troweling on the base coat is a speedier method.

    Problems with Plaster

    Crack Repair

    Foundation settlement, insufficiently sized joists, variations in seasonality and humidity, and improperly carried out repairs are all potential causes of cracks. Cracks can be as fine as a hairline or as big as a football field. 

    They may run perpendicular to the wall's surface in a straight line or follow the structural components in an angled pattern. 

    Plastering and drywall finishing are two different disciplines, but patching cracks in walls is a talent that lies halfway in between the two. 

    In other words, a willing starter can undertake simple repairs, and with practice, they can advance to more difficult undertakings.

    Hairline Cracks

    If a hairline crack has been visible over a period of time and does not move, remove the loose material and fill the crack with a coat or two of joint or spackling compound (or use an elastomeric product like Krack Kote). 

    If the crack continues to be visible after this process, the problem has been resolved. 

    Wait for each layer to completely dry before proceeding to the next step: lightly sand the surface. 

    Sand the patch down to a smooth finish using sandpaper with a fine grain on a sanding block.

    Wider Cracks

    Tape and the "float" technique should be used for larger fractures or cracks patched in the past without success.  

    First, apply significant force on either side of the fracture to ensure that the plaster is not shifting in any direction. 

    The next step is to examine the crack and determine whether one side of it has a higher relief than the other.

    Map Cracking or Extensive Cracks

    Cover the walls with sheets of adhesive-backed fiberglass mesh with an elastomeric coating, such as Nu-Wal, according to the directions provided by the manufacturer if you are dealing with a wide network of cracks or cracks in haphazard patterns known as map cracking. 

    Once the product is in place, there may still be some follow-up taping and filling that needs to be done.

    Moving Cracks

    Dig out the crack on the high or loose side of the plaster using a utility knife or a crack opener, which is a small hand tool. 

    This should be done if the plaster moves or if one side of the crack is obviously higher in relief than the other. 

    Take out a sufficient amount of material to get to the sound plaster.

    Remember that plaster will continue to shift even after it has dried. 

    Even if filling any fracture using a joint compound is not difficult, more cracks will appear near the repaired crack if the surrounding area is not made stable and separated from any other trouble spots.

    Before filling in the crack, most expert plasterers recommend first securing the side of the crack that is loose or high using plaster washers, wafer-thin perforated discs (see below), and drywall screws. These items are designed to refasten plaster to lath. 

    To begin, drill a few pilot holes at a distance of at least two inches away from each side of the fissure. 

    After that, secure the washers using screws that are 2 inches long.

    Can You Repair Plaster Walls Yourself?

    It shouldn't be too difficult for you to repair holes in plaster walls or patch them up on your own because the process is rather easy. 

    But before we go through the many different ways in which holes in plaster walls can be repaired or patched, it is important to review the three primary categories of plaster walls that you will most likely be working on.

    Plaster for solid walls often consists of lime-based plaster or a gypsum mix and is spread uniformly in numerous layers to cover exposed brick or block work in order to generate a smooth surface that is ready to be painted.

    Lath and plaster is a construction method that is commonly used in older homes. 

    Laths are narrow, well-seasoned wooden strips that are tightly together and attached to wall studs. 

    The lath is then covered with numerous layers of plaster to create a smooth, level wall or ceiling surface.

    Drywall is generally utilized in the process of constructing room partitions. Drywall sheets are normally attached to a wooden or metal stud frame by means of either screwing or nailing. 

    After the sheets are installed, drywall joint compound and tape are applied to the joints between the various boards to prepare them for painting.

    How Do You Fix A Small Hole In Plaster?

    When it comes to do-it-yourself projects around the house, preparation is often the difference between success and failure. 

    Therefore, before beginning to repair any holes or cracks in any plaster wall, you should cover the floor and any furniture with clean plastic sheeting and secure it with painter's tape. 

    Only then may you begin making repairs. 

    Keeping Your Work Area Clean

    Not only will this help protect the floor and the furniture from any plaster or joint compound that is spilled or splattered, but it will also make it easier to clean up since much of the dust from sanding will settle on the plastic sheeting instead of on the floor or furniture. In addition, make sure that any radiators in the room are turned off so that the plaster does not dry up too soon. 

    Additionally, make sure that any vents are covered so that sanding dust does not enter your HVAC system.

    Remember To Work Safely

    When sanding plaster, cutting plasterboard, or working with drywall, you should always prioritize safety and make sure to wear goggles and a dust mask. In addition, before cutting or sawing into any areas that need repair, you should always utilize a cable, pipe, and stud detector to ensure that the surrounding area is free of danger.

    When applying or mixing plaster, make sure to safeguard yourself by donning safety goggles, a dust mask, and protective gloves.

    Repairing a Hole in a Wall Constructed of Solid Plaster or a Wall Constructed of Lath and Plaster

    The key to attaining a high-quality finish when repairing a hole or patching a crack in either a solid plaster wall or a lath and plaster wall is to ensure that you remove all remnants of the old loose plaster, as well as any dust and grease, from the area that you are planning to fix. 

    This is true regardless of whether you are working on a lath and plaster wall or a solid plaster wall. 

    You can accomplish this goal by utilizing a metal or plastic scraper and a wire brush; however, you must not damage the surface around you. 

    After you have cleaned the area you are repairing of any remnants of old plaster and dust, you should apply a base coat made of a mixture of PVA glue and water to the surface that is around the repair.

    What To Use To Fill Holes In Plaster Walls

    When it comes to fixing a crack or patching a hole in a plaster wall, it is important to remember that many different fillers and plaster solutions are available on the market. 

    Additionally, application methods might vary from product to product; therefore, it is important always to check the instructions provided by the manufacturer. 

    Be sure to look for a product best suited for the task at hand; for instance, if you only need a little plaster to complete the repair, you might find using a ready-mixed plaster application easier. 

    Be sure to look for a product that is best suited for the task at hand.

    What Is The Best Way To Patch Plaster Walls?

    worker grinding white wall with sandpaper (1)

    Plaster has the potential to dry up rather rapidly; therefore, it is essential that you take your time and work with a tiny amount of it at a time on the hawk or board. 

    When you are ready to begin, cut a small amount of the wet plaster onto the plastering trowel and apply it to the repair using a smooth circular motion. Make sure to push hard to work the plaster into the damaged area. 

    Once you have completed these steps, you are ready to move on to the next step. When working with plaster, it is a good idea to keep a bucket of warm water nearby so that you can clean your trowel as you go. 

    This will help prevent any lumps from forming in the plaster and will cut down on the amount of work that needs to be done.

    When it comes to filler and plaster adhesive goods, it is important to be aware that some plaster and filler adhesive products shouldn't be applied to a depth that is greater than about 12 mm in a single application. 

    This is something that should be kept in mind. 

    If this is the case, it is possible that you will need to apply a second layer to the patch in order to seal the damaged area thoroughly.

    Achieving A Smooth Finish

    After allowing the plaster to dry as it would normally, moisten the surface of the plaster mix with clean water using a damp sponge or a soft paintbrush, and then produce a smooth finish by working the edge of a clean trowel across the plaster mixture to create a smooth surface.

    Ready For Painting

    For the purpose of getting the surface completely smooth before painting it, you should use sandpaper of a finer quality than normal and lightly sand the region where the repair was done. Before beginning the painting process, applying a sealer or priming paint to the existing wall is always a good idea. 

    This serves as a bonding agent and helps the finishing paint cling to the surface.

    Safety First

    Before fixing a hole in either drywall or plasterboard, inspecting the area around the repair using a cable, pipe, and stud detector is important. Doing so will guarantee that proceeding and cutting through the old plasterboard is safe. 

    Measure The Hole You Are Repairing

    After you have finished all the checks, you are prepared to start. To accomplish this, first measure the hole, and then using a clear marker, mark the dimensions of the hole on a scrap piece of plasterboard. 

    After you have determined the size of the hole that needs to be repaired, add an additional 25 millimeters to both the top and the bottom. 

    The offcut is then cut to size in a careful manner using either a plasterboard saw or a retractable knife. 

    Keep in mind that you should always operate safely you should always wear goggles along with a dust mask and try to work in a room that has adequate ventilation.

    The following step is to use a pencil and a straight edge to mark the original measurements (without the additional 25mm overhangs) onto the wall. 

    Once this step has been completed, draw diagonal lines from the hole into each corner. 

    After that, cut the plasterboard with a plasterboard saw along the diagonal lines.

    Removing The Excess Plasterboard Or Dry Wall

    After that has been completed, you will need a retractable knife and a straight edge to score the plasterboard along the guiding marks and then remove any excess plasterboard that has been scored.

    After the excess plasterboard or drywall has been removed, drill a hole in the center of the plasterboard offcut large enough to hold a nail, and then insert a nail into the hole you just drilled.

    Now go ahead and apply a bead of glue to the top and the bottom of the overhang of the offcut that measures 25 millimeters, and then carefully slide it through the hole and into position. 

    Pull the nail towards you as soon as it is in the correct position to form a secure connection between the glue and the plasterboard. 

    You must only remove the nail once the adhesive has successfully fused, and you must wait until the glue has completely dried before moving on. 

    You can pull the nail out of the adhesive once it has had enough time to dry, and it will fall behind the plasterboard wall.

    Almost Finished

    After that, combine the repair plaster or the ready-mixed filler, and apply it. 

    Putty should be applied to the hole with a clean, flexible putty knife. 

    It should be worked into the hole using a smooth, circular motion until it is filled and leveled with the surrounding plasterboard or drywall.

    Use medium-grade sandpaper and sanding block to create a smooth, level finish once the plaster or ready-mixed filler has been allowed to completely dry. 

    At this point, you are ready to paint the surface.

    How to Repair Lath and Plaster

    Fix the Lath

    Lath should be replaced if any lengths are missing, and all parts should be refastened. 

    Make sure to use drywall screws, and always drill pilot holes to prevent the wood from cracking. 

    If there is no stud available to anchor a lath end, slide a piece of lath into the hollow and screw it to the rear of the existing ones, parallel with the studs. 

    After that, you can attach new or loose lath to it by screwing it into place as though it were a stud.

    Stabilize the Wall’s Edge

    Drill holes around the damaged area using a masonry bit measuring 3/16 of an inch, spacing them every 3 inches and roughly 1 inch from the edge. 

    Drill until the bit comes into contact with the lath. If it does not go through, make a mark next to the hole with a pencil. 

    After that, you should spray plaster conditioner into the holes and then vacuum them. 

    After 15 minutes, use a squirt of plaster adhesive to fill in any holes that were not previously identified. 

    Remove any surplus with a cloth that has been dampened.

    Wet the Substrate

    Wet plaster will have its moisture drawn out by dry lath and the edge of the plaster that is exposed before it has a chance to set. 

    Applying a heavy coat of conditioner to the affected areas will stop this from happening. 

    Use a moist rag to clean up any drips or overspray that may have occurred. 

    Before moving on to Step 4, you must ensure that the conditioner has sufficient time to dry.

    Apply the Scratch Coat

    Plaster Magic mending plaster should be mixed in a clean bucket with cool water from the faucet until it reaches the consistency of natural peanut butter. Spread the mixture over the lath and up against the old plaster edge using a margin trowel, as demonstrated in the image. 

    Maintain a gap between this layer and the original plaster that is equal to half its thickness. 

    Make the patch look more rugged by using a scarifier to scratch it, and then remove any blobs that are on the wall.

    Trowel on the Second Coat

    After waiting for the scratch coat to get hard to the touch, which should take approximately an hour, you should mix up a second batch of plaster to have a somewhat thinner consistency—more similar to buttercream icing. 

    Employing a plastering trowel, level the mixture so that it is flush with the surface of the wall; next, remove any surplus from the wall. Please be patient and wait an additional hour for that coat to set.

    Smooth the Top Coat

    Scrape the patch area until it is smooth using a taping knife 6 inches long, then cover the patch with a thin coating of ready-mixed joint compound. 

    Allow to air dry over the night. After that, you should carefully scrape it smooth and apply another 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 motion. 

    The patch can now be primed and painted when it's ready.

    Conclusion

    Plaster walls can develop cracks, dents, or holes, but with the right tools and techniques, you can quickly patch and restore them. 

    A 3-Coat Plaster System begins with a substructure of lath and three coats of wet plaster. 

    A drywall is a uniform panel of gypsum plaster pressed between thick sheets of paper and can be nailed or screwed to wood or metal studs. 

    Repairing holes in lath and plaster walls requires good techniques and the right materials. 

    Patching cracked walls is a skill between plastering and drywall finishing and can range from hairline size to very wide. For hairline cracks, use joint or spackling compound, tape and “float” technique, map cracking or extensive cracks, and moving cracks. 

    Professional plasterers recommend securing the loose or high side of the crack with plaster washers, perforated discs, and drywall screws before filling in the crack. 

    Before starting, cover the floor and furniture with plastic sheeting and painter's tape. Wear safety goggles, dust masks, and protective gloves when sanding plaster, cutting plasterboard or drywall, and mixing plaster. 

    Remove old loose plaster and dust from the area and dampen it with PVA glue and water.

    Fill holes in plaster walls with a product that best suits your job. 

    Apply plaster using a smooth circular motion. 

    The most important details are to have a bucket of warm water, apply filler and plaster adhesive products to a depth of 12mm in one go, dampen the surface with clean water, prepare the surface for painting, use a cable, pipe & stud detector, measure the hole, cut the offcut, and remove excess plasterboard. 

    Drill a hole and place a nail into the center of the plasterboard offcut, then apply adhesive to the top and bottom of the 25 mm overhang. Mix and apply repair plaster or ready-mixed filler, then sandpaper and sand block to create a smooth finish. 

    Apply the Scratch Coat, Trowel on the Second Coat, Smooth the Top Coat, and Wait for the Patch to Dry before priming and painting.

    closeup hand worker plastering cement wall building house (1)

    Content Summary

    • Luckily, you can easily patch and restore your plaster walls with the right tools and techniques.
    • In this guide, we will walk you through the process of patching plaster walls, from preparation to the final finishing touches.
    • What is a 3-Coat Plaster System?
    • This article concerns itself with three-coat plaster, applied to wood or metal lath and troweled smooth.
    • It isn't as old as plaster, but drywall has a surprisingly long history, with early forms dating back to the late 19th century.
    • It's important to use good techniques and the right materials for lath and plaster repair.
    • It's a common practice to replace missing plaster with a piece of blue board (a wallboard made to be coated with plaster), but troweling on the base coat is faster.
    • Patching cracked walls is a skill that falls somewhere between the trades of plastering and drywall finishing.
    • Can You Repair Plaster Walls Yourself?
    • Repairing or patching holes in plaster walls is pretty straightforward and should be a job you can tackle yourself.
    • But, before we take you through the various ways you can repair or patch holes in plaster walls, it's worth reminding you of the three main types of plaster walls you'll likely be fixing.
    • So before starting to repair any holes or cracks in any plaster wall, you should cover the floor and furniture with clean plastic sheeting and fasten it using painter's tape.
    • Once you have removed any of the old plaster and dust from the area you're repairing, dampen the surface surrounding the repair with a base coat mix of PVA glue and water.
    • Because plaster can dry out quickly, it's important that you take your time and only work with small amounts on the hawk or board at once.
    • Achieving A Smooth Finish Allow the plaster to dry naturally, then use a damp sponge or a soft paintbrush to dampen the surface with clean water and then work across the plaster mix with the edge of a clean trowel to achieve a smooth finish.
    • Once you have measured the size of the hole you're going to repair, add a further 25mm to the top and bottom.
    • After removing the excess plasterboard or drywall, drill a hole that will accommodate a nail into the center of the plasterboard offcut and then place a nail into the hole.
    • Almost Finished Now mix and apply the repair plaster or ready mixed filler.
    • Apply to the hole using a clean, flexible putty knife, working smoothly in a circular motion until you fill the hole and level it with the existing plasterboard or drywall.
    • Stabilize the Wall's Edge Using a 3/16-inch masonry bit, drill holes every 3 inches around the damaged area, about 1 inch from the edge.
    • Drill until the bit hits the lath.
    • Vacuum the holes and spray them with a plaster conditioner.
    • Wait until the conditioner dries—about 20 minutes—before going to Step 4.
    • Apply the Scratch Coat In a clean bucket with cool tap water, mix Plaster Magic patching plaster to the consistency of natural peanut butter.
    • Rough up the patch by scratching it with a scarifier, then scrape any blobs off the wall.
    • Trowel on the Second Coat Wait until the scratch coat is firm to the touch—about an hour—then mix up a new batch of plaster to a slightly thinner consistency—closer to that of buttercream frosting.
    • Smooth the Top Coat Using a 6-inch taping knife, smooth the patch area, and cover the patch with a thin layer of ready-mix joint compound.
    • Let dry overnight.
    • Gently scrape it smooth and apply a second coat.
    • The patch is now ready to prime and paint.

    Frequently Asked Questions About Plaster Walls

    Repairing medium to larger-sized holes in plaster and drywall isn't quite as difficult as one might think. 

    Wall and ceiling repair patches made from fiberglass and perforated aluminum are excellent solutions that help to get the job done in just a few simple steps.

    However, a plaster filler like Polyfilla or a powder filler is the best option for filling plaster cracks, as alternatives such as caulk are best used for other purposes, like sealing gaps around pipes or tiles.

    Tiny holes in the plasterboard can be fixed with filler, but for holes bigger than about 12cm, you'll need to fit a plasterboard patch first so that the filler doesn't just fall embarrassingly into the cavity.

    For best results, keep the optimum temperature for plastering below 41 degrees Fahrenheit (5 degrees Celcius). 

    This will help to speed up the drying process, as well as help to minimize problems with cracking.

    You have to prime the new plaster before painting it. Freshly plastered walls are very dry, and such the moisture out of your paint. 

    Priming the walls with a mist coat first will ensure you end up with a great paint finish that doesn't flake or peel off.

    Google Rating
    5.0
    Based on 44 reviews
    Scroll to Top