How to Repair Cracked Walls Before Painting
interior painters adelaide painting over a cracked wall rarely solves the problem. If the crack is simply covered with paint, it can remain visible underneath the new coating or reappear after the paint has dried. For a smooth, professional-looking finish, cracked walls should be assessed and repaired before painting begins.
The right repair method depends on the type of wall, the size and location of the crack, and whether the damage is simply cosmetic or related to movement or moisture. Small cracks in plasterboard can often be repaired with filler and sanding, while larger or recurring cracks may require a more substantial repair.
This guide explains how to repair cracked walls before painting, how to prepare the surface, when to use filler or joint tape, and when a crack should be investigated rather than simply patched.
First, Identify What Caused the Crack
Before reaching for the filler, look closely at the crack.
Not every wall crack means the same thing. A fine surface crack in an older painted wall is very different from a wide crack that continues to reopen after repair.
Common causes can include:
- Normal movement of building materials
- Minor impact damage
- Movement around plasterboard joints
- Shrinkage or settlement
- Poorly finished joints
- Changes in temperature or moisture
- Moisture damage
- Movement around doors and windows
The location can also provide useful clues.
A small crack around a plasterboard joint may be a finishing issue, while a crack that repeatedly appears in the same location could indicate movement that needs further investigation.
If a crack is wide, rapidly getting worse, accompanied by sticking doors or windows, significant water damage or other signs of building movement, it is better to have the cause assessed before carrying out a cosmetic repair.
Small Cracks Can Often Be Repaired Before Painting
For minor cracks and surface imperfections, the basic process is relatively straightforward.
The area needs to be cleaned, loose material removed, filled, sanded and prepared for paint.
Australian plasterboard manufacturer Gyprock recommends removing protruding paint and paper remnants around minor damage, applying an appropriate repair compound, allowing it to dry and then sanding the repaired area ready for painting.
Step 1: Remove Loose Paint and Debris
Start by removing loose or flaking paint around the crack.
Use a scraper carefully to remove anything that is no longer firmly attached to the wall. Do not simply apply filler over loose paint because the filler will only be as secure as the surface underneath it.
For plasterboard, avoid damaging the paper face unnecessarily.
The goal is to create a firm edge around the damaged area.
Step 2: Clean the Area
Dust and other contaminants can interfere with adhesion.
The wall should be clean and dry before repair work begins. If the surface contains grease, dirt or other contamination, it should be cleaned using a suitable preparation product and allowed to dry.
Paint manufacturers such as Dulux specify that surfaces should be clean, dry and free from dust, oils, grease and loose material before painting.
This is particularly important in kitchens, laundries and other areas where walls can accumulate grease or moisture.
Step 3: Apply a Suitable Filler
Choose a filler that is appropriate for the wall material and type of damage.
For small cracks and dents in plasterboard, a ready-to-use or powder-based patching compound may be suitable.
Gyprock Rapid Patch, for example, is designed for small cracks, dents and other repairs in plasterboard, fibre cement, timber and masonry.
Apply the filler with a broad knife or filling knife and work it into the crack.
Do not create an unnecessarily thick mound of filler. Instead, feather the edges into the surrounding wall so that the repaired area can later be sanded flush.
Deeper or Wider Cracks May Need More Than Filler
Simply filling a larger crack may not provide a durable repair.
Where a crack involves a plasterboard joint or more significant movement, the repair may require joint tape and multiple coats of compound.
Gyprock’s repair guidance separates minor dents and scrapes from larger holes and damage, with the repair method changing according to the extent of the damage.
For plasterboard joints, reinforcing tape can help create a stronger finished joint when used with the appropriate jointing system.
When should you use joint tape?
Joint tape is particularly relevant when repairing cracks associated with plasterboard joints rather than simply filling a small surface imperfection.
The repair generally involves:
- Removing loose material.
- Preparing the joint.
- Applying suitable joint compound.
- Embedding the appropriate tape.
- Applying additional coats as required.
- Feathering the edges.
- Allowing the compound to dry.
- Sanding the finished area.
The exact system should follow the plasterboard and compound manufacturer’s instructions.
If the board itself has significant damage or movement, filling the visible crack alone may not address the underlying problem.
Sand the Repair Until It Blends With the Wall
Sanding is one of the most important stages when repairing cracked walls before painting.
A repair can feel smooth to the touch but still become obvious once paint is applied, particularly when light falls across the wall from a window or down a hallway.
After the filler has completely dried, lightly sand the area until it is flush with the surrounding surface.
Avoid aggressive sanding that creates a depression or damages the surrounding wall.
Run your hand over the repair and look across the wall from different angles. If you can clearly see a ridge or hollow before painting, it is likely to remain visible after painting.
For a high-quality finish, the transition between repaired and original surfaces should be as subtle as possible.
Prime the Repaired Area Before Painting
A repaired section can absorb paint differently from the surrounding painted wall.
That difference in porosity can produce visible patches or variations in sheen after the topcoat is applied.
Dulux specifically recommends spot-priming repairs containing filler before applying its Wash&Wear interior topcoats.
Primer or sealer can therefore be an important part of the repair rather than an optional extra.
The appropriate product depends on the surface and paint system. Bare plaster, porous repairs, stains and previously painted surfaces can each require different preparation products.
For example, Dulux’s Precision Sealer Binder is designed to seal porous and powdery surfaces and provide a suitable foundation for subsequent coats.
Always follow the paint manufacturer’s preparation instructions.
What If the Wall Has Water Damage?
Do not treat a water-damaged crack like an ordinary cosmetic crack.
Moisture can weaken plasterboard, cause paint to peel and contribute to mould growth. If the source of moisture remains, repairing and repainting the wall without fixing the cause can result in the damage returning.
Gyprock states that plasterboard exposed to substantial wetting should generally be replaced, while minor water exposure requires the board to be allowed to dry and then inspected for deterioration or warping.
Potential sources of moisture can include:
- Plumbing leaks
- Roof leaks
- Bathroom moisture
- Condensation
- External water penetration
- Failed seals around wet areas
If the wall is soft, swollen, warped or significantly water damaged, replacing the affected section may be more appropriate than filling the crack.
Cracks in Bathrooms and Wet Areas Need Extra Attention
Cracks in or around wet areas deserve particular attention because they can potentially allow moisture to reach parts of the wall system that should remain protected.
Gyprock’s installation guidance states that cracks or damaged areas in tiled areas that could allow water into the wall cavity should be repaired promptly.
If the problem involves cracked tiles, failed grout or damaged sealant rather than simply a painted wall, repainting is not the appropriate first repair.
The moisture path needs to be addressed before decorative painting.
When Should You Call a Professional?
DIY repair can be appropriate for small cosmetic cracks and minor plasterboard damage.
Professional assessment becomes more appropriate when:
- The crack is large or widening.
- It repeatedly returns after repair.
- There are several significant cracks.
- The wall appears to be moving or distorted.
- Doors or windows have started sticking.
- There is substantial water damage.
- Plasterboard is swollen or weakened.
- The crack extends through masonry.
- The damage may involve structural movement.
- The wall is part of a fire-rated system.
Large plasterboard repairs can involve replacing sections of board rather than simply filling the damaged area. Gyprock also provides different repair methods depending on the size and severity of the damage.
If you are unsure whether a crack is cosmetic, getting it assessed before painting can prevent you from spending money on a finish that may need to be repaired again.
Preparing the Entire Wall Before Painting
Once the cracks have been repaired, don’t immediately start rolling paint.
Inspect the rest of the wall for:
- Nail holes
- Dents
- Scratches
- Flaking paint
- Uneven patches
- Previous repairs
- Surface contamination
- Differences in texture
Dulux recommends filling imperfections and cracks, sanding repairs smooth and removing dust before applying preparation products or topcoats.
A good final preparation process is:
Repair → dry → sand → remove dust → prime/seal → inspect → paint.
Taking the time to inspect the wall before the final coats can reveal imperfections that would otherwise become much more obvious once the new paint is applied.
Common Mistakes to Avoid
Painting directly over the crack
Paint is not a substitute for filler or joint repair. The crack may remain visible or reopen.
Filling over loose paint
If the surrounding paint is unstable, the repair can fail along with the old coating.
Using too much filler
A thick mound creates more sanding and can leave an obvious patch.
Skipping primer
Filled areas can absorb topcoat differently from the surrounding wall, creating visible differences in appearance.
Sanding too aggressively
Over-sanding can create a depression or damage plasterboard paper.
Ignoring recurring cracks
If the same crack keeps returning, investigate the cause instead of repeatedly covering it.
Painting over moisture damage
Repair the source of moisture and assess the condition of the wall before repainting.
Frequently Asked Questions
Can I paint directly over small wall cracks?
It is better to repair the crack first. Even fine cracks can remain visible through a new coating, particularly under strong side lighting.
What filler should I use for wall cracks?
Choose a filler designed for the specific wall material and repair type. Plasterboard, masonry and timber may require different products. Always follow the manufacturer’s instructions.
Do I need to sand after filling a crack?
Usually, yes. Once the filler has dried, sanding helps create a smooth transition between the repair and the surrounding wall.
Do repaired cracks need primer?
Often, yes. A spot primer or suitable sealer can help equalise the repaired area’s porosity before the topcoat. Follow the paint manufacturer’s system.
Why does my wall crack keep coming back after painting?
A recurring crack may indicate movement, an unresolved plasterboard joint issue, moisture or another underlying problem. Repainting repeatedly without identifying the cause may not provide a lasting repair.
Can I repair a large wall crack myself?
Some larger cosmetic repairs can be undertaken as DIY projects, but significant, widening or recurring cracks should be assessed first. If the wall itself is damaged or movement is suspected, professional advice is preferable.
Final Thoughts
Repairing cracked walls before painting is about more than making the wall look smooth. The repair needs to address the type of damage, prepare the surface correctly and create a stable foundation for the new coating.
Small cosmetic cracks can often be repaired with suitable filler, careful sanding and appropriate spot priming. Larger cracks, recurring damage, moisture problems and significant plasterboard deterioration require more careful assessment.
If your walls have multiple cracks or the same areas continue to fail after previous repairs, consider having the surfaces inspected before starting the painting project. A professional painter can also identify preparation work that may be needed to achieve a consistent, durable finish.
