Crack in your walls? Here’s what to do!

Johannes van Graan Johannes van Graan
Exterior Renovation Kgodisho Solutions and Projects Classic style houses
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A crack in a wall now and again is natural, but when is it cause for concern? Just look at houses and buildings right here in South Africa and try counting the number of wall cracks you discover. Most of those are not serious and are simply due to slight settlement of the structure’s foundations, mortar shrinkage, or tiny roof movements. 

Then again, there are certain cracks that can be potentially dangerous, seeing as they result from significant foundation issues, water penetration, or major roof movements. 

Let’s delve a bit deeper into the issue of wall cracks – and what to do about it!

1. When is a wall crack dangerous?

Wall cracks, according to the National Home Builders Registration Council (NHBRC), can be classified as follows: 

• Crack width under 1mm – slight problem – normal decoration for repairing. 

• Crack between 1 and 5mm – minor issue – normal decoration for repairing. 

• Crack between 5 and 15mm – moderate problem – normal repairs / minor masonry replacement required. 

• Crack between 15 and 25mm – severe concern – extensive repair work / replacing wall sections required. 

• Wider than 25mm – very dangerous – major repair work / partial rebuilding required.

2. Cracked walls: Fixing drywall

Got a crack in a drywall somewhere? You’re in luck, for drywall is the easiest of the three wall types to rectify. 

With a utility knife, cut a 3-6mm V-notch along the length of the crack. Vacuum out all debris and dust. Use either mesh joint tape or joint compound and paper tape to cover the crack. This should be followed by a thin layer of joint compound, extending roughly 5cm on each side of the tape. Allow to dry. Afterwards, apply a second coat of joint compound, feathered about 15-17cm on either side of the crack. Let it dry overnight. The next day, lightly sand the surface until smooth to make the wall ready for paint or wallpaper.

3. Cracked walls: Patching plaster wall

House Swart (Cameron Court Unit 1) Swart & Associates Architects Walls
Swart & Associates Architects

House Swart (Cameron Court Unit 1)

Swart & Associates Architects

Minor cracks in plaster can be treated similar to drywall, with joint compound. But if the plaster is pulling away from the lath, the wall must first be shored up with a conditioner spray and adhesive.

First, drill holes with a 4.76mm masonry bit that will penetrate the plaster but not the wood lath, every 7cm along the crack’s length. Vacuum all dust and debris from the drilled holes. Spray the adhesive conditioner into each hole and allow dwell time as per the manufacturer’s instructions.

Inject the adhesive into each hole, starting from the lowest point. Use a damp sponge to clean up excess adhesive. Using a drill, immediately attach plaster rings to pull the plaster tight against the wall. Allow to cure according to manufacturer’s instructions.

Remove the plaster rings. Using a coat of joint compound, hide the holes and original crack. After lightly sanding the surface, apply a second coat of joint compound. When dry, sand the surface smooth.

4. Cracked walls: Concrete

An epoxy repair kit is required to repair a crack in a concrete wall, as the epoxy will ensure a watertight seal in the crack.

Start your repair process by tapping 7-cm finish nails partially into the crack every 30cm – these nails will attach injection ports. Epoxy comes in two parts, A and B, which will need to be mixed just before using. Make sure you mix equal parts of the epoxy on a scrap piece of wood with a putty knife. Apply a small amount of the mixed epoxy on each injection port tab; then, by covering each of the finish nails with one port, attach each port against the wall.

Spread the mixed epoxy over the crack, covering about 2cm on either side. Make sure to cover the flange of each injection port with epoxy as well. To feather the epoxy at the edges, use a paintbrush dipped in mineral spirits. Leave it for about 6 – 10 hours. 

With a caulk gun, inject liquid concrete repair into the ports, starting at the bottom. Inject until liquid oozes from the port. Ensure to plug each port before moving on to the next one. Allow to cure for at least five days, then, using a hacksaw, cut the port flush with the wall.

5. Cracked walls: Repairing deeper damage

Concrete Lovers Minimal Studio Dining roomAccessories & decoration
Minimal Studio

Concrete Lovers

Minimal Studio

If wall cracks in drywall or plaster are deeper than 6.40mm, it’s recommended to first fill the crevice with a filler compound prior to taping with joint compound. Mix the compound according to the manufacturer’s instructions. Fill the crack until it is flush with the rest of the wall’s surface. Then cover with tape and joint compound (as instructed earlier) to achieve a smooth wall surface.

6. Cracked walls: Signs of structural damage

Concrete walls are load-bearing walls, especially in a foundation. And although it is easier to patch minor cracks (hairline cracks), major problems are a sign of poor structural integrity.

Note that a horizontal crack stretching the length of a wall is definitely evidence of serious damage. Don’t even try and DIY these types of cracks – always rely on a professional to rectify the issue the correct way.

One such professional to rely on is Kgodisho Solutions and Projects, based in Pretoria. This seasoned construction company is a dynamic, multi-disciplinary firm accredited with the NHBRC, and is known for providing an array of construction services across the Gauteng region. Building renovations might be their core focus, yet they are experienced enough for any form of project requiring alterations, extension, and renovations.

Some of their most popular services include:   

• Building,    

• Painting,    

• Kitchen and bathroom designs,    

• Built-in cupboards,    

• Paving and decking,    

• Wood/laminate flooring,    

• Plastering,    

• Waterproofing,    

• Roof designs and repairs, and many others. 

Done fixing a crack? Let’s move on to Painting Walls: 6 Ideas You've Never Thought of Before!

Where in your house is a little wall crack waiting to be DIYed?

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