How To Patch Plaster | Advice from Restoration Experts
If you’re looking for how to patch plaster online, it’s vital that you read all instructions carefully and ensure you’ve prepped surfaces needing repairs before you start applying patching compound. Plaster ceiling crack repair and other such fixes are not as easy as putting drywall tape over those cracks and filling them in with putty, as plaster is built in layers and needs to be repaired accordingly.
To patch plaster walls or ceilings:
- Remove all broken and loose plaster all the way to the lath behind the plaster.
- Vacuum out any residual dust.
- Cut a patch of mesh the size of the hole and nail it to the lath.
- Spray the lath with water to moisten it. Start applying a plaster layer.
- Once the first layer is dry, continue adding layers until the crack is filled.
Plaster repair is often more involved and difficult than homeowners realize, and especially so for large, deep cracks. Chunks of missing plaster might also need a bit more attention than hairline cracks, while water damage often requires lath repair or full-scale plaster replacement as well.
Before you attempt DIY plaster repair in your home or business, you might note some added details about how to patch plaster properly and ensure a quality repair that lasts. It’s also helpful to note when you’ll want to call a plaster repair contractor near you, so your home is always in good condition and your repairs blend seamlessly with the surrounding walls or windows.
What Is the Best Way to Repair Plaster Walls?
Even if you’re experienced in drywall repair, you might note some added tips for how to patch plaster walls and ceilings, as these materials are vastly different and need different tools and materials for proper fixes. Remember that it’s good to invest in the cost of a plaster repair contractor near you if you suspect these fixes are too difficult or outside your area of expertise.
- Your first step is to prep the space with a scraper. Scrape and chip away any flaking plaster until you reach fresh, clean plaster. Don’t worry if you make the chip or crack larger, as this is often needed to provide a base for fresh patching compound.
- As you chip at broken or damaged plaster, ensure you don’t break or otherwise push through the wood strips or lath behind the plaster. That lath provides a base for plaster and must be in good condition to hold existing plaster and your patching material.
- Remove any dust and debris on the existing plaster and area needing repairs. Use a stiff-bristled brush or even a vacuum cleaner hose if needed. New plaster can’t attach to dust, so ensure you have a clean surface for new patching material.
- Once the surface is prepped as needed, only mix up as much patching material as needed for each layer as you work, to the consistency of cake batter. Plaster patching material begins to set and dry once mixed, so don’t mix it all at once!
- Use a wide wallboard knife and spread a 1/4” layer of patching material over the crack or chip. As that first layer begins to set, cross-scratch it so that the second layer adheres well.
- For larger chips or chunks of missing concrete, use drywall tape or repair mesh over that first layer, to help hold it in place and provide a solid base for the next layer.
- Once the first layer is dry, apply a second 1/4” layer. Continue to cross-scratch, allow the layer to dry, and mix and apply a new layer as often as needed to fill the damaged area.
- Ensure the last layer is fully set and dry, then sand the area lightly before painting as needed.
Can You Use Drywall to Patch Plaster?
Drywall or joint patching compound is sufficient for filling in hairline cracks along plaster walls and ceilings. For larger chunks, however, can you use drywall to patch plaster or provide a base for new patching material.
To use drywall to patch plaster, remove damaged and flaking plaster and prepare the area as instructed above. Once you have a clean, dry space, measure the depth of existing plaster; insert a putty knife into the crack or chip, using your finger to mark how far it slides into the wall, and then measure that length. Most plaster is 1/2” to 3/4” thick, although it might be slightly deeper.
Once measured, buy a sheet of drywall to that thickness. You’ll want to cut a piece of drywall to fit the crack or chip. If needed, measure the damaged area and draw a rough outline on a piece of paper. Trim the paper until it matches the area needing repairs and then trace that shape onto your drywall.
To cut drywall, score the front with a knife and snap it along that cut. You can then cut the backing with a utility knife. Screw this drywall patch into the lath behind the existing plaster, taking care not to chip or break those wood pieces. Use drywall screws for a secure fit.
After you’ve secured the drywall patch, apply drywall or fiberglass mesh tape around the edges. Use a flat blade to apply drywall patching compound over the screws and tape; add more layers as needed, smoothing each one as you work. Once dry, use 120-grit sandpaper to smooth the patched area and then paint as needed.
Can You Fix Plaster Pulling From the Lath?
The wood strips or lath behind plaster provides the fresh, wet material with a foundation for it to adhere and then dry and set. When plaster pulls from that lath, it’s vital you schedule fixes as quickly as possible; if that lath should break, or the plaster pull from it completely, your wall or ceiling could outright collapse!
Before performing repairs, however, it’s vital that you determine the cause of sagging plaster. If a home has settled and shifted, reattaching and strengthening plaster adhesion is sufficient for a safe, thorough repair. Push the plaster back with your hand; if it lays flat in position and seems to fit back into place, this usually indicates that the lath is in good condition.
To repair this plaster, you’ll need to bore holes through to the lath behind it. Ensure you create these holes in the lath and not the spaces between those wood slats, as the adhesive you inject needs to stick to the lath itself. Use a 1/4” carbide drill bit, to ensure holes are large enough to hold adhesive but small enough to keep plaster in good condition.
After drilling, gently vacuum away dust and debris, being careful not to upset any existing plaster. Inject the holes with an acrylic or latex adhesive; even Liquid Nails or floor tile adhesive is sufficient! Don’t inject too much as this might cause the plaster to shift in place, but use just enough to fill your drill holes. Use a damp sponge to wipe away excess.
If you try to push sagging plaster back into place and you hear a popping sound or feel it shift and move, this might indicate water damaged lath and the need for professional repairs! Water leaks or trapped humidity behind walls lead to damaged wood, including a wood lath, and injecting adhesive is typically insufficient for needed repairs. It’s also vital that you address needed plumbing fixes or inadequate ventilation before performing these repairs.
In many cases a plaster repair expert near you will remove sagging sections of plaster altogether and then replace damaged lath behind it. Adding wire mesh also provides strength and stability to plaster, reducing weight on the lath. Installing new plaster ensures a safe and secure ceiling or wall surface.
Can You Patch Plaster Medallions?
If decorative medallions or other details are suffering hairline cracks, fill these in with spackle or joint compound, ensuring you keep the finished surface smooth so the repair disappears into that design. However, if those details have larger chips or cracks or even missing chunks, it’s best to call a plaster repair contractor near you! He or she will typically make a mold of the design and create new sections of it for replacement, to ensure the finished product looks like new.
Can you repair plaster walls with spackle?
Tiny, hairline cracks along plaster walls and ceilings are not unusual, as plaster moves out of position and then shows minor cracks or chips. A homeowner might fill in those small cracks with spackle or joint compound, and then smooth it over with sandpaper and paint. However, use new plaster compound or plaster repair mix for larger cracks and to fill in severely damaged plaster sections.
How do you fill screw holes in plaster walls?
Use plaster repair compound to fill in screw holes along plaster walls. Apply this compound with a wide, flat knife and then use sandpaper to smooth the surface once dry. Paint as needed.
Should you replace plaster with drywall?
While drywall is often easier to install and repair than plaster, authentic plaster walls and ceilings, especially when decorated with medallions and other details, might add value to your home or commercial structure. Plaster offers a natural look and feel not easily duplicated with drywall, and is easy to maintain once you know how to patch plaster surfaces and keep that material in good repair.