You don’t need to be an expert to repair cracks, dents, or holes in walls and concrete caused by various issues in your home. In this guide, we explain practical methods and materials you can use to fill holes and fix cracked walls. Plus, at the end of the page, we answer many common questions about wall crack repairs.
How to Repair Holes and Cracks in Walls and Concrete
When repairing a hole or crack in a wall, it’s important to use the right material based on the size and cause of the damage. Start by determining whether the crack is caused by paint or plaster, then choose the appropriate repair method. Keep in mind that different materials may be required for fixing holes versus cracks.
Some fine cracks in walls may result from paint issues. In such cases, light sanding may be all that’s needed. However, if the plaster or wall itself is damaged, a more thorough repair will be necessary.
To fix holes and cracks in walls, you can use ready-made repair putty, finish plaster, skim coat, polyurethane sealant, or even paint. But which one should you choose for different types of cracks? Let’s break it down.
1-Ready-to-Use Wall Fillers
Ready-made wall crack fillers are excellent for quick repairs. Sold in toothpaste-like tubes or buckets, they are ideal for fixing hairline cracks, small gaps, and holes in walls.
These fillers are similar to plaster and have a consistency close to pre-mixed plaster. Apply the filler directly onto the hole or crack using a putty knife, spread it evenly, and allow it to dry completely. Once dry, sand the area with 180-grit sandpaper. After sanding, you can apply primer and paint to achieve a smooth, professional finish.
2-Polyurethane Sealants
Polyurethane sealants are similar to silicone, but their main purpose is to fill gaps. Since they are paintable, polyurethane sealants are a great option for sealing wall cracks.
They are also weather-resistant, making them suitable for both indoor and outdoor use. These sealants work well for cracks or plaster damage about the width of a pencil. Apply the sealant using a caulking gun, let it dry for 24 hours, and then cover it with plaster or wall filler before painting. Alternatively, you can paint directly once it dries.
Sealants come in acrylic and polyurethane types. Compared to other sealants, polyurethane types provide better stretch, superior bonding, and enhanced durability. However, for fine hairline cracks, ready-made wall filler or satin plaster is often a better choice.
3-Finish Plaster
If the crack is as thin as the tip of a pencil, finish plaster is a good option. This is one of the most commonly used methods for repairing wall cracks. For deeper or wider cracks, use base coat plaster first. For fine, shallow cracks, satin plaster (a smoother, thinner type of finish plaster) is ideal.
Before painting, wall cracks should be repaired with finish plaster. Mix the plaster with water until it reaches a soft, dough-like consistency, then apply it using a metal spatula. After it dries completely (usually within a day), you can prime and paint the surface.
If you’re using finish plaster to cover wall holes, proper preparation and consistency are key. While this method takes more effort than using ready-made filler, it’s better suited for large repairs. For bigger areas, satin plaster may be a more economical option.
Finish plaster is also ideal for surfaces with peeling paint or small holes. It acts as a final coat that creates a smooth, uniform finish. Knead it thoroughly with a spatula before applying, then sand with 180, 200, or 220-grit sandpaper after it dries. Finish with primer and paint.
4-Base Coat Plaster
Base coat plaster is a thicker type of plaster used to fill large gaps, such as holes the size of a fist or larger. It’s often spread across the whole wall surface prior to applying the finish plaster.
If cracks are 3–4 inches wide or more, base coat plaster is the best option. Once the base coat is dry, apply a skim coat on top for a smoother finish. Then sand, prime, and paint.
5-Paint
Minor plaster repairs may leave visible marks. In these cases, painting can help blend the repaired area. For small cracks in paint, a few coats of paint may be all you need. Simply sand the area with 180-grit sandpaper and repaint. Be aware, though, that there may be some color difference between the old and new paint.
What is The Best Way to Fill Cracks in Walls?
The best way to fill cracks in walls depends on the size and type of crack:
For Small Hairline Cracks
Use wall filler or spackling paste. Apply with a putty knife, smooth it out, let it dry, then sand before painting.
For Medium to Large Cracks
Use joint compound and drywall tape. Spread a layer of joint compound, place drywall tape over it for reinforcement, and apply another coat on top. Sand smooth once dry.
For Deep or Wide Cracks
Start with bonding plaster or base coat plaster to fill the crack. When dry, cover the area with a thin layer of finish plaster to achieve a smooth, paint-ready finish.
For Movement-Related Cracks
If cracks are due to structural movement or settling, use flexible polyurethane sealant. It allows for expansion and contraction without reopening.
For Paint Cracks
Lightly sand the area and repaint. Use multiple coats if needed to cover the damage.
How do You Permanently Fix Cracked Walls?
- Prepare the Crack: Clean the crack and remove any loose material.
- Apply Joint Compound: Spread compound over the crack.
- Embed the drywall tape into the wet compound to strengthen the crack repair.
- Add More Compound: Cover the tape with another layer and smooth it out.
- Cover with More Compound: Allow the area to dry fully.
- Sand the Area: Use fine-grit sandpaper to even out the surface.
- Prime and Paint: Apply primer and paint to blend the repair with the rest of the wall.
Frequently Asked Questions
Below, we’ve answered the most frequently asked questions about wall crack repairs. If you have any other questions about wall crack repair, feel free to ask.
How to Repair Deep Cracks in Plaster Walls?
To repair deep cracks in plaster walls, start by cleaning the crack to remove any loose plaster and debris. Next, use a utility knife to widen the crack into a V-shape, which helps the repair material adhere better. Press bonding plaster firmly into the full depth of the crack to ensure a strong repair. Once the bonding plaster has set, apply a finish plaster or skim coat over the area to level the surface. Allow the plaster to dry completely before sanding it smooth. Finally, prime and paint the area to match the surrounding wall.
Can I Just Paint over Cracks in Walls?
Deep cracks need to be repaired before painting. However, if the crack in the wall is caused by the paint, you can simply sand it with a fine-grit sandpaper and paint directly.
Can You Plaster over Cracked Walls?
Yes, you can plaster over cracked walls. First, clean the crack and remove any loose material. If necessary, widen the crack for better adhesion. Apply a bonding agent for deep cracks, then spread plaster over the crack using a putty knife. Even out the surface and let it dry fully. Once dry, sand the area and finish with primer and paint for a seamless repair.
Does Primer Fill in Cracks?
Primer can cover fine paint cracks. However, before using primer, the cracked wall needs to be sanded. Applying multiple coats of both primer and paint can also help cover the crack.
How to fill in Hairline Cracks?
To fill in hairline cracks, start by cleaning the crack and removing any loose debris. Apply a thin layer of wall filler or spackling paste with a putty knife, pressing it into the crack. Smooth the surface and allow it to dry completely. Once dry, sand it lightly to create a smooth finish, then apply primer and paint to blend the repair with the rest of the wall.
What is The Best Filler for Cracked Plaster?
The best filler for cracked plaster is a plaster repair compound or joint compound. For deep cracks, use bonding plaster to fill the gap and ensure a strong bond. For surface-level cracks, finish plaster or ready-to-use wall fillers work well to smooth out the surface. These fillers provide strong adhesion, flexibility, and a smooth finish for a long-lasting repair.
