Updated on Oct. 07, 2024
Plaster walls crack and hanging art on them can be a challenge. These tips and tricks from an expert make living with plaster walls easier.
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Whether you view plaster in an old house as a blessing or a curse, like original floors, windows or architectural millwork, it’s a valuable part of the fabric of an old home — and it needs care. If you’re living with plaster, you know it requires some special considerations to keep looking its best.
Traditional plaster — a simple mixture of lime, sand, horsehair and water — has existed for at least 14,000 years. Plaster that’s actively maintained can last hundreds or even thousands of years.
A carbon-neutral and self-healing material, plaster has many advantages over gypsum products like drywall. Learning to appreciate your home’s plaster as a valuable resource, just as you would its other sought-after original details, will give you another reason to love your old home.
Plaster offers greater sound attenuation, mold inhibition and insulating qualities over gypsum drywall. Often installed over wood lath from old-growth forests, plaster can handle a leak without getting ruined.
Best of all, old plaster was applied by talented craftspeople who used their skills and abilities to create your home. Appreciating, caring for and retaining your plaster walls requires you to take a hands-on role, and it ensures more of your home will exist for future generations.
I’ve spent the last two decades learning how to repair, restore and maintain the traditional lath and horsehair lime plaster in my homes. So I can offer you some pragmatic and cost-effective advice on how to manage your plaster.
Over the years I’ve made my fair share of mistakes and learned to overcome them. Throughout, I’ve determined where to find the right materials, and which approaches for repair and restoration work best for me.
Whether you’re a plaster purist or someone just trying to hang a picture without creating a new crack, I hope these tips help you appreciate, care for and live with your plaster walls.
You’re proudly hanging your first picture on your new home’s antique plaster walls. A few minutes later, it’s no longer hanging. And now you now have a bent nail, a large hole and a new diagonal crack.
Spare yourself the agony and grab your drill and the right weight-rated angled Ook hooks.
Attach a 1/16-in drill bit to create a pilot hole for the hook’s nail. Hold the hook as a guide to drill your pilot hole(s) at the correct angle. Gently tap the hook and nail into the wall.
If the nail encounters a piece of lath, the pilot hole will let it pass without damage. If there’s no lath, the angle of the nail and the plaster structure should be sufficient to hold the frame.
To keep your walls looking pristine, consider installing picture rail molding around the upper perimeter of your room. Then you can suspend your wall hangings from the rail with hooks and wire made for this purpose. When your preferences change, swap out or move things with no nail holes to repair.
Modern stud finders simply don’t work on plaster walls. Stud finders use a magnetic sensor to find screws holding drywall to the studs just below the wall’s surface. But thick plaster on wood lath is held to the stud by small nails that are nowhere near the surface. Standard stud finders just aren’t sensitive enough to detect them.
So rather than a traditional stud finder, use the StudPoP magnetic stud finder. This little device comes with a super strong magnet that detects those little lath nails deep below the surface.
When the magnet encounters lath nails, a plastic pin (it looks like a board game piece in the center of the tool) pops up and makes an audible “pop.” Hands down, this is the best product to find studs in a lath and plaster wall.
There are two ways to repair a large hole in plaster, one traditional and one that’s a modern compromise.
The traditional method uses lime plaster with goat hair. It’s applied to the strips of wood, called lath, that are attached to the framing.
When applied, the plaster pushes through the gaps between the lath strips in lumps that harden to create the new “plaster keys.” This “scratch coat,” the plaster’s first coat, establishes the bond with the lath. Before the first coat fully hardens, it’s also scratched in zigzag patterns using a scarifier, roughing the surface for the next coat to bond to.
Following a cure time of several days, apply the second coat, or the “brown coat.” This will completely fill the hole and bring the patched area up to the level of the old surface.
Finally, applying a finish coat of lime putty to blend the patch with the old plaster will make the wall sound again. The advantages are material compatibility and longevity, while the drawbacks are the work’s complexity and the plaster’s expense. We’ll cover exactly where to find these traditional supplies in the “How To Source Plaster Supplies” section below.
A modern repair/patching approach utilizes modern gypsum-based material. You cut a drywall patch, screw it to the lath, and apply a plaster bonding agent like Plaster Weld to prep the surface. You may use gypsum plaster such as Structolite, joint compound or Plaster Magic patching plaster, along with tape, like FibaFuse, to bridge any gaps and bring the patched surface flush. Then apply a finish coat of joint compound.
Ease of obtaining materials is the big advantage here. The drawbacks are potential future cracks from using gypsum materials with lime plaster.
Repairing cracks in plaster can be intimidating, but it’s not difficult and needs a light touch.
The first step is correcting any underlying issue that caused the crack, or it will return. Plaster tends to crack because of stress, resulting in the plaster “keys” breaking and no longer supporting the wall properly. To resolve this issue, grab a stabilizing adhesive like Plaster Magic.
Begin by drilling holes through the surface of the plaster, but not through the lath. Next, spray the Plaster Magic Conditioner into the hole, then inject Plaster Magic Adhesive into the hole and between the plaster and lath. Finally, screw large plastic washers through the holes and lath to clamp the plaster back onto the lath.
After 24 hours, when your wall is stable, remove the washers.
Next, use a taping knife to remove any loose portions of plaster or high spots. Fill any gaps with a plaster patching compound with fibered seam tape. You can use lime putty to keep material consistency, but sandable joint compound will also work if you’re using gypsum products.
For many electrical projects, adding a receptacle or switch in a plaster wall often creates a mess. Not to worry, there’s an easier way.
I like to use “old work” boxes with clips that hold them in place. After marking the location for the junction box with an outline, use an oscillating tool to cut the plaster (not the lath). Then pry the plaster out of the hole with a small pry bar exposing the lath.
Switch to a jigsaw to cut the lath about 95 percent through on either side of each piece, leaving just a little wood to stabilize the lath.
Next, place a drywall screw in the middle of the lath and hold it with pliers while you make the rest of the cut. This keeps the jigsaw from causing vibration damage.
Finally, secure any loose/floating lath to the plaster using Plaster Magic adhesive. Let it cure, then place your junction box. If your plaster and lath are thick and the tabs won’t clamp, swap the box’s screws with #6 pan head screws that are two or three inches long to extend the clamping tabs.
Plaster that’s been around for 100 or more years has likely been covered by wallpaper and/or paint many times over. If you’re fully restoring your plaster and want it to stand the test of time, you must return your plaster to its raw base.
Plaster is resilient and unaffected by applying steam to the surface. A wallpaper, garment or heavy-duty steamer softens old layers of wallpaper and applied texture, like popcorn ceilings, for removal without damaging the underlying plaster.
While steam also works for paint removal, I have the most luck with chemical strippers — specifically, Smartstrip and Peel Away 1.
Smartstrip is less aggressive and tends to work well on modern latex paints. Peel Away 1 will remove a dozen or more layers of paint with a single application, so it’s great for older paint. Peel Away 1 also keeps the paint in a paste or liquid form, so airborne particles are less likely.
Both work while wet, so covering with Peel Away paper or wax paper extends their active life. Peel Away 1 does alkalize the surface, so neutralizing with the included pH balancer is required.
You can’t beat the immediate gratification of paint, but painting plaster requires some considerations you don’t encounter with drywall.
Because old plaster is often lime-based, it naturally absorbs and releases ambient moisture, which can cause modern acrylic latex paint and primer to bubble and fail. And you’re probably painting over existing layers of paint that may have already been compromised. As with most paint projects, preparation is key.
If the prior paint is thick and failing, it must be removed. To completely remove paint, refer to the section above. If the paint is mostly well adhered, remove the peeling portions. Be sure to take safety precautions when you risk dealing with lead paint.
Apply a thin coat of plaster, aka a “skim coat,” over any heavily textured surface with an appropriate restoration product like Master of Plaster. Then select and apply an alkyd or oil primer before applying your chosen paint color. As long as you’re following these steps in priming, you can topcoat with your preferred paint.
If your plaster is bare, select a paint that will let lime plaster breathe. Whether we’re talking clay paint, like those from Eathborn Paints or Fenwick & Tillbrook, or a traditional limewash finish, the key is a permeable surface covering that doesn’t inhibit the plaster’s ability to release moisture.
Like many old house features, plaster is maintainable and can be repaired rather than replaced when a problem occurs.
Plaster cracks or other common failures are often due to underlying structural or water intrusion issues that have been neglected and must be addressed. The most significant aspect of caring for your plaster is maintaining your home proactively.
Beyond issue resolution, ensuring plaster can remain breathable is the next most important step. Nonpermeable insulation (like closed-cell spray foam) behind plaster walls and a solid painted surface create a plaster sandwich that results in eventual failure.
Caring for plaster means choosing the right building materials for wall coverings and insulation that will maintain the vapor permeability of lime plaster.
The final aspect is limiting unnecessary vibrations and impacts that could damage the plaster. Hammering nails, broken door stops, slamming doors and running in the house are all enemies of plaster. Do you think your grandparents yelled at you about those activities to improve your manners? No. It was probably to protect their plaster!
Have you ever heard the term tadelakt? It’s an ancient Morrocan method of using lime plaster on interior and exterior walls to produce a waterproof surface. Given its unique look and physical characteristics, tadelakt has experienced a rejuvenation of sorts.
To achieve this result, you only need a few key elements — lime-based plaster, black soap, carnauba wax and special rubbing stone to polish the finished plaster smooth and waterproof.
Tadelakt does require some special care, like using appropriate non-bleach cleaners. But the time-honored approach provides a traditional finish that’s unique from the tile, stone or fiberglass shower enclosures found everywhere today.
Obtaining the right materials to care for your historic plaster is truly half the battle. Specialty lime plaster products are not available at big box stores and home centers, so you need to know where to look.
It took me many years and much research to find the suppliers that I trust. When shopping for plaster, my three go-to sources are:
Master of Plaster: Located in Columbia, South Carolina, the Master of Plaster team offers high-quality ready-mixed restoration and finish plaster. It’s the most user-friendly plaster with incredible results, but it’s also the most expensive.
Lancaster Limeworks: Located in Lancaster, Pennsylvania, Lancaster Limeworks offers traditional high-calcium lime plasters and masonry mortar that can be used for plaster or historic masonry. I use their products when building up a traditional scratch and brown coat over salvaged lath.
Limeworks.us: Located in Telford, Pennsylvania, their vast array of products includes natural hydraulic lime plasters suitable for repairing, restoring or applying new plaster.
All three companies have incredibly knowledgeable staff who are eager to help.
If you’re interested in learning more about how to restore, repair or apply new plaster, you have several great options. You could follow in my footsteps and use trial and error with YouTube videos and online plaster discussion groups as your guides. But I’d advise against that.
Instead, Lancaster Limeworks and Limeworks.us offer periodic hands-on multi-day workshops that teach the tricks of the trade. Short of taking a sabbatical and becoming a plasterer’s apprentice, these workshops are your best options to lay the foundation for you to become a plaster expert in your home.
How often have you heard, “That plaster is too far gone, it has to go!” In my experience, I’ve dealt with plaster that’s “beyond repair,” only to bring it back from the brink.
Restoring badly damaged plaster involves three phases.
Stabilization: Using an adhesive product such as Plaster Magic allows you to re-secure cracked areas and loose plaster to sound lath. For lath that’s pulled away from the studs, re-secure using plaster buttons. The goal is to ensure the plaster is sound, not bouncy.
Prepare and repair: Remove any loose or peeling paint, or strip the surface bare. If the plaster has any large holes or missing sections, repair it with lime plaster. You are preparing the plaster for the skim coat.
Skim coat: I use a three-coat process of Limeworks.us Takcoat with embedded fiberglass screen, Master of Plaster base coat and finish coat. The Takcoat adheres without a bonding agent; it’s the decoupling layer that prevents future cracks. The final coats achieve a smooth finish. Best of all, no sanding means no dust.
Many of us have encountered a discolored area on a plaster wall or ceiling due to a leak. You identify and stop the leak, but then what? Does the damaged plaster need to come out?
The beauty of lime plaster is that it’s not nearly as fragile as paper-faced drywall or gypsum plaster. A little water infiltration is no match for lime plaster. It inhibits mold growth that traditionally impacts damp paper on drywall because plaster can dry completely without mold or compromise.
The key is to remove any sagging, failed or affected paint so the plaster can breathe and release that moisture. Use a moisture meter to determine when the readings are similar to dry sections of your plaster, then refer to the “How To Paint Plaster” steps to finish your repair.
As much as lime plaster is a traditional building material, fresh plaster must be handled carefully. Lime can be a caustic irritant and gloves are necessary when handling new plaster.
The recipes for plaster have changed some in modern times, as have the paints used to cover plaster surfaces. In the mid-1900s, unsafe manufacturing additives were used as binders, and lead paint covered plaster surfaces.
If your plaster was applied in the mid-1900s and you plan to disturb it, it’s important to send off a small sample for lab testing before you begin demo. Likewise, if your walls were painted before 1978, testing for lead paint and taking proper precautions are necessary if you’re disturbing the paint.
HEPA filtration and vacuums, negative air machines, plastic containment coverings, approved hazardous waste disposal practices and proper particulate respirator masks all play an important role in safety.
