Hairline cracks and holes in plaster walls are unsightly, aren’t they?
But that’s not what worries you the most.
You’re probably thinking:
Has it gone kaputt?
Do I need to replace it altogether?
I can’t say we blame you. Damaged plaster has an aspect of finality to it. And the notion of carrying out repairs or replacing plaster walls sounds like it’s a lot of work, not to mention costly.
Thankfully, fixing hairline cracks in plaster walls shouldn’t be a major cause of concern. It’s at least the case most of the time. If you can believe it, it is easier to repair than its more popular counterpart. Yes, drywall is harder to repair.
Yes, you can patch it with minimal expense and effort. All you need is some knowledge on how to do it the right way.
As to that, we’ve got you covered.
Ready? But before we get started, here’s a bit of background on what it is. We’ll talk about how it’s made before we get started on repairing those hairline cracks in plaster walls.
Table of Contents
How to repair hairline cracks in plaster walls
It goes without saying: the smaller the crack, the easier it will be to repair. It’s at least as long as the plaster is still securely attached to the lath inside the wall cavity. How do you determine if it is about to break away from the lath? Simple: give it a gentle push. Is it moving in a way that seems like it will break away from its foundation? In that case, you must contact a specialist who can install a new plaster for you.
But if it feels like it’s going to hold, then good on you. However, you still need to patch it up. Here are the steps to do that:
How to repair hairline cracks in plaster
- Widen it.
The first step to fixing a small crack is to widen it. Grab a putty knife or a lever-type can opener. Stick the point inside the crack, and open the edges to about ⅛ of an inch. That should give the joint compound some wiggle room for later.
- Brush off the dust.
Clear the affected area of dust or any dirt sticking to it. Dip a medium-bristle brush in a TSP and water solution and gently brush away any crumbs or dust from the crack.
- Cut strips of tape.
Measure and cut short lengths of paper drywall tape or fiberglass mesh joint tape and then cover the crack. It bears noting that this should be done before applying a compound to prevent folds and bumps from forming. Use scissors when cutting to ensure that the tape doesn’t have ragged edges. It allows for smoother application and prevents the compound from invading the crack.
- Apply the joint compound.
Applying a joint compound is an essential step to ensure a great finish. Dip your putty knife into the compound and then use it to smooth the tape over. Do this at least twice to ensure that the tape is adhering nicely around the crack.
- Apply the joint tape.
Apply the tape to the crack and then smoothen it with your putty knife. Don’t overdo it, or you risk scoring the tape. Once the tape is evenly applied, leave the joint compound to dry for a few minutes.
- Apply another layer of joint compound over the tape.
You don’t want the taped area to be visible once you’re finished, so you can apply another layer of joint compound over the tape. It makes sure that it extends a few inches past the tape’s edges. Once the joint compound is fully dry, sand it down with 8-grit sandpaper to make the joint compound blend nicely with the surrounding areas.
- Prime it.
Apply latex primer over the area to make it easy for topcoat paints to adhere to the surface. Once the primer is fully dry, apply the top coating over the surface. Always refer to the product’s instructions to determine dry-off time. To make everything match, use the same paint color as the surrounding area.
The Inverted V Method
- Open the crack to an inverted “V” shape (like a dovetail) and remove any excess dirt and debris. Doing this will give the patch a foothold to cling onto.
- Cut strips of drywall tape and adhere it along the crack’s length.
- Apply some moisture on the lath and plaster surrounding the area. This will allow the patch to stick to the surface.
- Apply at least two layers of mixed joint compound over the crack. Then sand it down with fine sandpaper until the surface is smooth enough.
- Gently push the compound with a trowel to make sure that the newly applied plaster is adhering securely to the lath.
- Apply at least two coats of joint compound. Don’t forget to sand the surface between coatings.
- Apply the final layer of joint compound to create a smooth and seamless base for the paint.
- Paint over the surface if you like.
Holes
Here are the steps to patching up holes in plaster walls.
- Remove any excess debris, dirt, or plaster from the hole. Cut off any dangling pieces. If the edges are rough or jagged, smooth them out with sandpaper. To remove remaining dirt, wipe the hole’s interior and exterior with a clean rag.
- Cut a portion of self-adhesive fiberglass mesh that is big enough to cover not just the hole but also the areas extending 2-3 centimeters past around its perimeter. Center the mesh over the hole and make sure that it’s at least in close contact with the wooden lath inside. If the mesh is non-adhesive, nail the mesh to the wooden lathe inside the hole.
- Apply a ready-mixed filler over the area with a spatula or a putty knife. Allow some of the filler to pass through the holes of the mesh until it’s all filled up. Make sure that the area around the sides of the mesh is completely covered. The idea here is to completely seal the affected area so that it will blend well with the surrounding area. Once the hole is fully patched up, remove any excess filler by brushing at them with a downward stroke of the putty knife or spatula.
- Use fine sandpaper to gently sand the area until it’s smoothed over.
- Apply another layer of ready-mixed filler over the area. Wait for it to dry.
- Brush off any excess dirt or dust with a clean rag.
- Paint over the area if desired.
Wide cracks
Using a joint compound won’t be enough to patch up the damage for wider or bigger cracks. Do the following steps to repair bigger cracks in your plaster.
- Using a masonry bit, drill 2.54 centimeter-holes about 1.5 inches from both sides of the crack’s edges and 3 inches apart.
- Apply some adhesive along the holes using a caulk gun before removing any excess adhesive with a sponge.
- Secure washers into the holes by driving a 2” drywall screw into each one.
- Leave the adhesive to dry before removing the washers.
- Patch it up with a drywall knife.
- Install a crackstop fabric repair mesh over the damaged area.
- Apply two layers of coating and sand gently.
Why They Occur
While durable, even plaster walls can incur damage through wear and tear and poor maintenance. Before we delve into how to repair hairline cracks in plaster walls, let’s go over why they happen in the first place.
To be sure we’re on the same page, let’s define what a “hairline crack” is. To put it simply, it is a line that appears along the surface of a wall. It’s not just plaster. It indicates a split that appears as if it is breaking apart. Small hairline cracks are not usually a cause for concern, but they must be addressed as soon as possible before they get worse.
A wide range of things can cause them, and they include:
- Poor installation
- Seasonal changes
- Shrinkage
- Corrosion
Poor installation
Sadly, some contractors won’t follow building codes because they can get away with it. At the same time, some are not competent or diligent enough to do the job properly.
Either way, it’s you who loses.
So many things can go wrong when constructing it. For instance, a construction professional might forget to rake the background surface before applying plaster. Another possible scenario is when he or she overlays it without applying chicken wire mesh in the masonry first.
Whatever the reason for the poor installation, a crack is something you can’t afford to ignore.
Seasonal changes
One drawback of using it is that it’s vulnerable to moisture. Moisture becomes prevalent in the atmosphere when seasons change frequently. Allow moisture to come in contact with it regularly, and it will seep through. It causes it to expand and form damage.
Shrinkage
Water from freshly applied plaster tends to evaporate rapidly, reducing the surface layer’s volume. This volume reduction causes it to shrink, resulting in the formation of cracks in the surface layer. To prevent shrinkage from appearing, always check if the plaster has been cured and sanded thoroughly before application.
Corrosion
Using concrete that is of poor quality contributes to corrosion. Weak concrete has a porous surface, making it easy for moisture to seep inside. Once the moisture comes in contact with the cement for too long, the protective layer holding the structure together becomes corroded. It causes hairline cracks to form. Ones caused by corrosion can be even more annoying than the regular ones because of their rusty color.
Foundation shifts
Natural disasters such as earthquakes and hurricanes can produce stresses in the wall’s foundation. It causes cracks not just on the surface but also the structure itself. Ones due to foundation shifts are more likely to expand since the source of the damage is coming from the subsurface.
Vegetation growth
Do you have large trees or vines near your home? You might want to check if they’re growing into your plaster. If cracks result from growing vegetation, you can trim the “excess growth” with pruning shears.
Settlement
Cracks can occur when the house “settles” long enough to create stresses in the home’s foundation, causing the plasterwork to shift. It leads to cracks. They are usually vertical and likely run along the home’s exterior. Ones caused by settlements should not be taken lightly because they may lead to structural problems. It will be wise to have them investigated immediately upon discovery to ensure that the structure of the home hasn’t been compromised in any way.