10 Steps to Fixing Wall Cracks
Wall cracks signal potential structural issues, which pose risks to a building’s stability due to settling, temperature changes, or structural movements. Although cracks are common, it is vital to understand what causes them and promptly address them.
Timely repair is essential to prevent further damage and maintain structural integrity. Here’s a brief guide to effectively fixing wall cracks and ensuring long-lasting durability for your building.
Make Sure It Is Not a Structural Issue!
It’s crucial to speak with a structural engineer about large wall cracks. The engineer will evaluate the extent of the cracks, locate structural hazards, and discover underlying causes such as instability or foundation issues.
To maintain the building’s integrity and tenant safety, engineers provide specialised solutions to reinforce buildings, implement possible fixes, and avert future problems.
Understanding Wall Cracks
- Foundation Settling: Over time, buildings naturally settle. This settling can cause minor shifts that lead to cracks in walls. These cracks are often vertical and may not indicate severe structural issues but should be monitored and repaired.
- Temperature Changes: Fluctuations in temperature can cause building materials to expand and contract. This thermal movement can result in cracks, especially in areas where different materials meet, such as at the junction of walls and ceilings.
- Structural Movements: Buildings experience various loads and stresses, including those from wind, seismic activity, and the weight of the structure itself. These forces can cause structural movements that lead to cracks.
- Wear and Tear: Everyday wear and tear, including the natural ageing of building materials, can cause small cracks over time. While these are often superficial, they should still be repaired to prevent further deterioration.
Tools and Material Needed
| Tools | Materials |
| Drop cloth | PVA (Polyvinyl Acetate) mix (1 part PVA, 2 parts water) |
| Safety gloves | Bonding Coat Plaster |
| Safety glasses | Polyfilla (for a smooth finish) |
| Wire brush | Paint |
| Milwaukee Multi-Tool (for stubborn parts) | |
| Dust brush | |
| Clean bucket | |
| Trowel | |
| Putty knife (for smaller cracks) or scraper (for larger cracks) | |
| Rubbish bag | |
| Multi-Tool Attachements | |
| Cloth | |
| Paint Brush | |
| Paint Kettle Bucket | |
| Paint Roller with Tray | |
| Paint can Oppener/Stirrer | |
| Hoover |
Step-by-Step Guide for Wall Crack Repair
Step 1: Preparation and Safety
- Lay down a drop cloth on the floor to protect it.
- Put on safety gloves and safety glasses.
Draper 83714 3.6 x 2.7m Laminated Cotton Dust Sheet
Predator PUUH-13 Coloursafe Emerald Gloves (Size 10 / XL)
Bolle Safety BOLSILEXPSI SILEX Safety Glasses – Clear
Step 2: Cleaning and Preparing the Wall Crack
Tools needed:
- Wire brush
- Milwaukee Multi-Tool
- Dust Brush
Instructions:
Using a Wire Brush: Start by manually scrubbing the wall crack with a wire brush. This tool effectively loosens and removes any loose bits of plaster, debris, or old paint from the crack.
Using a Milwaukee Multi-Tool: Attach the appropriate tool to your Milwaukee multi-tool. Depending on the nature of the crack and the material involved, choose from the following attachments:
- Sanding Platen Blade: Ideal for smoothing rough surfaces or removing paint.
- Sharp Scraper Blade: Useful for scraping away stubborn debris or old plaster.
- Flexible Scraper: Effective for reaching into tight corners or angles.
Cleaning Stubborn Parts: Switch on the Milwaukee multi-tool and gently guide the attachment over stubborn parts of the crack, applying light pressure. Move the tool back and forth to gradually remove any remaining loose material or tough residue. Be cautious not to apply too much force, which could damage the wall surface.
Dust Removal: Once the wall crack is cleaned of debris and loose bits, use a dust brush or a clean cloth to remove all the dust.
| If your wall crack is small, skip steps 3, 4, and 5 and go directly to Step 6, followed by Step 7 (Polyfilla); however, PVA protects the wall crack from cracking again. |
Milwaukee M18 FMT-0X 18V FUEL Multi-Tool (Body Only)
Sealey WB05Y Wire Brush Stainless Steel
Faithfull FAIPBDUST Dusting Brush 100mm (4 in)
Step 3: Applying PVA Mix
Tools and Materials Needed:
- PVA (Polyvinyl Acetate) mix (1 part PVA, 2 parts water)
- Brush
Instructions:
- Prepare a PVA mix by combining 1 part PVA with two parts water.
- Brush a thin layer of the PVA mix into the crack. Let it dry until it’s tacky, about 80% dry (not completely dry, but not too wet).
Illbruck WD120 Weather Proof PVA 5kg
Stanley STASTPPDS3Z DynaGrip™ Set of 3 Synthetic Brush Pack
Step 4: Preparing Bonding Coat Plaster
Material and Tools Needed:
- Trowel
- Clean bucket
- Bonding Coat Plaster
Instructions:
- Start by putting some cold water in a bucket (not too much).
- Always add the bonding plaster to the water, not vice versa.
- Gradually add bonding plaster to the water using a trowel, mixing against the sides of the bucket to achieve a creamy consistency (flowable but not runny).
| After mixing the bonding plaster, you have about 30 to 40 minutes of working time before it begins to set. Make sure to apply it within this window for the best results. |
Faithfull FAI3GBUCKET Bucket 14 Litre/ 3 Gallon (Black)
Ragni R129SG Soft Grip Gauging Trowel 7in
Faithfull FAIST107 Professional Putty Knife 38mm
Step 5: Applying Bonding Coat Plaster
Materials and Tools Needed:
- Putty knife (for smaller cracks) or scraper (for larger cracks)
- Wire brush ( If needed for multiple layers)
- The bonding coat plaster mix from the previous step.
Instruction:
- Apply the bonding coat plaster to the crack using a putty knife for smaller cracks or a scraper for larger ones.
Putty Knife (for smaller cracks):
- Load a small amount of bonding plaster onto the trowel.
- Take the needed amount with a putty knife.
- Press the plaster into the crack, ensuring it fills the entire depth of the crack.
- Smooth the plaster over the crack with the flat edge of the putty knife.
- Remove any excess plaster and ensure the surface is flush with the surrounding wall.
- Take the needed amount with a putty knife.
Scraper (for larger cracks):
- Scoop an appropriate amount of bonding plaster onto the trowel, then transfer the necessary amount onto the scraper.
- Apply the plaster to the crack using a firm, sweeping motion.
- Fill the crack with the plaster, ensuring it extends slightly beyond the wall’s surface.
- Use the flat edge of the scraper to level the plaster, smoothing it evenly across the crack.
- Remove excess plaster as you go to maintain a neat application.
- Only apply up to 8mm thick at a time.
- If the crack is deeper, apply in multiple layers, allowing each layer to dry for around 2-3 hours before adding the next.
- After each layer, use a wire brush to roughen the surface lightly (after 2-3 hours).
- Reapply the PVA mix and wait until it becomes tacky before applying another layer of bonding plaster.
- You can apply up to 3 layers, ensuring the total thickness does not exceed 25mm (2.5 cm).
- When you finish, allow the bonding coat plaster to dry completely for 24 hours. This step is crucial for achieving a professional finish in your home improvement project.
| If your wall crack is small, skip steps 3, 4, and 5 and go directly to Step 6, followed by Step 7 (Polyfilla); however, PVA protects the wall crack from cracking again. |
Step 6: Sanding
Tools Needed:
- Milwaukee Multi-Tool with the right attachment (sanding platen blade)
- Cloth
Instructions:
- Prepare the Multi-Tool: Attach the sanding attachment to the multi-tool according to the manufacturer’s instructions.
- Sanding the Wall: Use the multi-tool with the sanding attachment to gently sand the surface of the dried bonding plaster.
- Move the sanding attachment in smooth, circular motions to achieve an even finish.
- Pay attention to areas where the bonding plaster meets the existing wall surface, ensuring a smooth transition.
- After Sanding, remove the dust with a cloth.
Faithfull FAIMFKIT10 Multi-Function Tool Mixed Blade (Set of 10)
Sealey CC71 Sheen Microfibre Cloth
Step 7: Applying Polyfilla
Materials and Tools Needed:
- Polyfilla
- Scarper (filling knife)
Polycell PLCMPPR1KGS Multi Purpose Polyfilla Ready Mixed 1kg
Instructions:
- Prepare Polyfilla: Take a small amount of Polyfilla onto the filling knife.
- Positioning the Filling Knife: Hold the filling knife at a 45-degree angle to the wall where the crack or hole is located.
- Applying Polyfilla: Press the Polyfilla firmly into the crack or hole using the filling knife.
- Smoothing the Surface: Smooth the Polyfilla evenly across the repaired area, ensuring it fills any depressions and blends seamlessly with the surrounding wall.
Step 8: Painting Preparation
Materials Needed:
- Mist coat: 1 part water, 3 parts paint (always check for the manufacturer’s instruction)
- Paintbrush
- Paint kettle
- Paint can stirrer
Instructions:
- Prepare the Paint: Stir the paint thoroughly in its container to ensure consistency before mixing the mist coat.
- Mixing the Mist Coat: In a paint kettle or bucket, combine 1 part water with three parts well-stirred paint. Mix thoroughly to achieve a uniform solution.
- Preparing the Brush: Dip the paintbrush into the mist coat mixture, ensuring it’s adequately loaded but not dripping.
- Applying the Mist Coat: Start at one edge of the repaired area and apply the mist coat with smooth, even strokes.
- Work in sections, overlapping each stroke slightly to ensure thorough coverage.
Stanley Tools STA429932 Plastic Paint Kettle 2.5 litre
Stanley STA126102 Max Finish Mini Roller Kit 100mm
Sealey PA05 Paint Can Opener/Stirrer – Pack of 5
Step 9: Painting
Tools and Materials Needed:
- Paint
- Paint Roller with Tray
- Paint kettle
- Paint brush and Tray
- Paint can stirrer
Instructions:
Mix the Paint: Use a paint stirrer to thoroughly mix the paint in its container until it reaches a uniform consistency.
Mixing the Paint: Use a paint stirrer to thoroughly mix the paint in its container until it reaches a uniform consistency.
Using a Paint Brush:
- Dip the paintbrush into the paint in the kettle bucket, ensuring it is adequately loaded but not dripping.
- Begin painting along the edges and corners of the repaired area, using smooth and even strokes.
- Feather the edges to blend the paint seamlessly with the surrounding wall.
Using a Paint Roller:
- Pour paint from the kettle bucket into a paint tray.
- Dip the paint roller into the tray, rolling it back and forth to distribute the paint on the roller cover evenly.
- Start rolling the paint onto the wall in a “W” or “M” shape to ensure even coverage.
- Work in sections, overlapping each stroke slightly to avoid visible seams.
Finishing Touches: Allow the first coat of paint to dry completely according to the manufacturer’s instructions. If necessary, apply additional coats, following the same method and allowing each coat to dry before applying the next.
Step 10: Cleanup
Tools Needed:
- Hoover
- Cloth
Draper 90107 15L Wet & Dry Vacuum Cleaner 1250W 230V
Instructions:
- Remove the drop cloth from the floor to expose the cleaned area.
- Use the Hoover to thoroughly clean up any dust and debris from the work area.
- Optionally, use a cloth to wipe down surfaces for a final clean finish before completing your project.
FAQ
What happens if I don’t wait 24 hours for the bonding plaster to dry?
If you don’t wait 24 hours for the bonding plaster to dry completely, several issues can arise:
- Poor Adhesion: The subsequent layers of plaster or paint may not adhere properly to the surface, leading to peeling or flaking.
- Cracking: The bonding plaster may crack as it continues to dry under subsequent layers, compromising the repair’s integrity.
- Uneven Surface: Incomplete drying can result in an uneven surface, making it difficult to achieve a smooth and professional finish.
- Mould and Mildew: Trapped moisture can create a breeding ground for mould and mildew, especially in damp or poorly ventilated areas.
- Extended Drying Time: The overall drying time for the entire repair process will increase as the moisture from the bonding plaster will still need to evaporate.
Allowing the bonding plaster to dry completely for 24 hours ensures a durable and professional-quality repair.
Can I skip the mist coat and just paint directly over the Polyfilla?
No, applying a mist coat before the final paint is important. The mist coat helps seal the filler and creates a smooth, even surface for the topcoat of paint.
Can I use other tools if I don’t have a Milwaukee Multi-Tool?
While a Milwaukee multi-tool is recommended for its versatility and efficiency, you can use other suitable tools, such as a manual scraper, sander, or other multi-tools.
What safety precautions should I take during this repair?
Wear safety gloves and safety glasses to protect yourself from dust and debris. Ensure the room is well-ventilated, and use a dust mask if necessary.
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