How to Fix Cracks in Plaster Walls

Small cracks often appear on walls and ceilings over time and the reasons are many. Vibrations from nearby traffic, wear and tear, ageing of the plaster and so on. Fortunately, hairline cracks are not a serious structural problem and can be fixed relatively easily.

So if you:

• Recently purchased a home, which has some cracks on one of the walls.
• Are planning to repaint your walls and want to repair any hairline cracks beforehand.
• A small spot has cracked on your wall after painting and you want to fix it.

Then read along and learn how to fix cracks in plaster walls.

Tools for repairing plaster walls

Before starting this task, be sure to equip yourself with the following tools and materials.

• Dust sheet
• A Stanley knife
• Vacuum cleaner
• Patching compound
• Sandpaper – two kinds, medium and fine
• A sanding block
• A scraper
• A paintbrush
• Primer
• Sponge

How to fix hairline cracks in plaster walls

Small cracks of this sort don’t pose a cause for concern and are easy to fix.

1. Lay a dust sheet – Do this before starting to fix any cracks in the plaster wall, regardless of how big or small they are.
2. Enlarge the hole – use your Stanley knife and dig out the cracks a little bit. The point is to form a V-shaped groove. Cut the plaster until you no longer see the original crack.
3. Vacuum the groove – the groove must be completely clean of any fine dust and debris.
4. Prepare the patching compound – mix some filler powder with water and stir until it becomes a thick paste. You can be sure it’s thick enough when you put your scraper into it and it doesn’t sink to the floor of the bucket.
5. Dampen the groove – use a damp sponge or a spray bottle. The patching compound will stick better if it’s slightly wet and this will stop the plaster from sucking out the moisture from the filler too quickly.
6. Fill the groove with the compound – use your scraper to both apply the material and scrape any excess. You don’t need to make the surface absolutely flat.
7. Wait for the compound to dry – this may take anywhere from 12 to 24 hours. Check the manufacturer’s instructions to make sure.
8. Sand the surface – wrap your sanding block with medium-grade sandpaper and sand the surface. Afterwards, use the fine-grade paper.
9. Prime the repaired area – using your paintbrush, apply the primer onto the repaired crack. Why is this important? The filler will absorb the paint much faster than the rest of the wall, that’s why it needs to be primed. Otherwise, you will see the repaired spot after having it painted.

The hairline crack in the plaster wall is now fully repaired and ready for painting. Congratulations! Also, even though you’ve laid a protective sheet on the floor, you still need to clean the floor. Check out our post on how to clean plaster dust, if you need any information on this topic. It certainly has its specifics.

How to repair holes in plaster

For holes in your plaster wall, you will need to purchase a mesh tape with adhesive on the backside and a piece of plasterboard.

1. Cut a piece of plasterboard – make it a square shape. Place this piece on the plasterboard where the hole is and outline its shape with a pencil.
2. Cut the plasterboard – use your Stanley knife and cut the wall following the outline. Place the piece inside to check if it fits as good as it should. Afterwards, remove it.
3. Clear out the hole – remove any debris, dirt or plaster and cut off any dangling pieces with your Stanley knife. Sand any sharp edges and go over the hole with a damp cloth to remove any fine dust and dirt.
4. Cut a piece of fibreglass mesh – Place your plasterboard piece inside the now clean hole. Cut four strips of mesh and stick each one around the plasterboard piece.
5. Apply a joint compound – you can apply it with your scraper. Cover the entire area of the new plasterboard piece along with the mesh. The point is for it to cover the damaged spot so well, that it blends completely with the rest of the wall. Make a thin coat.
6. Leave the compound to dry – afterwards, you will have to make 2 more coats, again very thin and wait until they dry.
7. Sand the area – use some fine sandpaper and work the surface to make it smooth.

If the hole is smaller, like the size of a coin, then you can carry out the process, but without using a piece of plasterboard. Just glue a piece of mesh tape on the hole and apply joint compound. Repairing holes in plaster can be difficult, which is where you might benefit from a hard surface repair if it seems too difficult.

How to repair chipped plaster corners

External corners in modern homes usually have metal strips that protect them from damage and add extra durability. Older homes, on the other hand, have no such things and your external corner can be easily chipped away by an accidental hit. Fortunately, they are as easy to repair as they are easy to break.

1. Brush the damaged area of any loose dust.
2. Dampen the damaged plaster with either a moist sponge or a spray bottle. Do not soak it.
3. Apply some filler to the damaged spot using your scraper. Be sure not to leave any voids whilst applying the filler compound.
4. Level the filler by running the scraper up and down the surrounding plaster on both sides of the corner.
5. Run your finger down the repaired spot to form its corner. Do this as it begins to harden. You will notice that the rest of the external corner is not completely sharp, so this spot shouldn’t be either.

It is quite possible that the filler may start to shrink as it dries. This is normal, but you need to act by applying a new filler and levelling it. You may have to do this several times.

How to fix cracks in corners of plaster walls

There are two things to know about cracks in inner corner walls:

• If it is a fine crack, meaning the crack is exactly in the corner and doesn’t deviate from it, you can easily fill it with paintable caulking and be done with it.
• If the crack does deviate from the corner to one side, you will need to use paper tape.

This is how you fix cracks in corners of walls:

1. Brush the damaged area of any dust and loose material.
2. Apply joint compound along the crack on both sides of the corner. Apply a thick coat, otherwise, the drywall tape might not stick properly.
3. Cut a piece of tape in the length of the crack.
4. Crease the tape and carefully put it into the corner. Push it gently down, it will stick
5. Grab your scraper and start scraping the extra compound from the middle of the tape to its sides. The point is to have no compound around the tape edges but to keep all the compound underneath the tape.
6. Apply a fast-drying joint compound over the tape and around its edges. Use your scraper. If you have one with a larger size, even better. Apply a thin layer only and wait until it dries. Apply the compound on the two sides of the corner and wait until it dries.
7. Add the final coat. Start above and below the last coat.
8. Sand the area with fine sandpaper and you’re ready for painting.

Hire a professional

If the task of fixing cracks in your plaster walls seems too complicated or the problem is more serious than a hairline crack or a small hole, then call a professional. Fantastic Services works with skilled tradesmen, who have years of experience and are fully equipped to complete the job. Our professional plastering services include plaster repairs, as well as plasterboard installation, wall plastering, skimming and rendering. Call us today and get your plaster fixed as good as new!

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Did you fix the damage on your plaster wall? How did it go? Let us know by leaving a comment!

Image source: Shutterstock / VanoVasaio