Getting walls ready properly makes a huge difference to the final paint job. If you can see nail holes, hairline cracks or patchy repairs once the paint goes on, the finish will look rough even if you use a top-quality paint from Dulux, Taubmans or British Paints. The good news is that most small surface defects are easy to fix with the right filler, a bit of patience and proper sanding.
This guide covers how to fill nail holes and cracks before painting in a typical Australian home, whether you are patching plasterboard, plaster, fibre cement sheet or timber trim.
Start By Checking What You’re Repairing
Before you reach for the filler, have a close look at the surface. Nail holes in plasterboard are usually simple cosmetic repairs. Hairline cracks in cornices, cornices joints or along plasterboard seams can be movement-related and may need flexible patching compounds. If the crack is wide, keeps reappearing, or is near doors, windows or structural elements, it may point to ongoing movement in the building. In that case, a painter can often advise, but a builder or plasterer may be needed if the issue is more than surface deep.
For homes with fibre cement products such as James Hardie sheets, or older plaster walls, use a filler suited to the surface. Read the label carefully at Bunnings or Mitre 10 and match the product to the material you are repairing.
What You’ll Need
- Spackling paste, interior filler or patching compound
- Flexible filler for fine cracks
- Putty knife or filling blade
- Sandpaper or sanding sponge in fine grades
- Dust brush or vacuum
- Paintable gap filler or caulk for small joins
- Primer or undercoat, if required
- Drop sheet and dust mask
For larger repairs, you may also need a mesh patch, setting compound or a plaster repair kit from a local hardware store.
How To Fill Nail Holes And Small Dents
First, make sure the area is clean and dry. Remove any loose paint, dust or crumbling material. For tiny nail holes, press a small amount of filler into the hole with a putty knife, then scrape off the excess so the patch sits just proud of the wall. For slightly larger holes or dents, apply the filler in thin layers rather than trying to fill the whole gap at once.
Let the product dry as directed on the packaging. Drying time depends on the product type, the temperature and ventilation. Once dry, sand lightly with a fine sanding sponge until the surface feels smooth and blends into the surrounding wall. Wipe away the dust before painting.
How To Repair Hairline Cracks
Hairline cracks need a little more care than nail holes. Start by opening the crack slightly with a scraper or utility knife if the product instructions suggest it. This helps the filler bond properly. Remove dust, then apply a paintable flexible filler or crack repair compound along the line of the crack. Smooth it off with a filling knife or a damp finger if the label allows it.
If the crack is where two materials meet, such as wall and skirting, a flexible paintable gap filler is often better than hard filler because it can cope with minor movement. For wider cracks, you may need to apply compound in stages or use reinforcing tape before patching.
Let It Dry, Sand It Back, Then Prime
Patience matters here. If you sand or paint too early, the patch can shrink back and show through the finish. When the filler is fully dry, sand the repair flush with the wall. Run your hand over the area to check for ridges, pinholes or edges you may have missed. A second thin coat is often better than one thick coat.
Once the repair is smooth, prime bare filler before topcoating. This helps stop the patch flashing through the final colour, especially on walls that will be painted in a darker colour or finished with low sheen paint. On porous surfaces such as plaster or raw filler, primer is especially important.
Choosing The Right Product For The Job
| Repair Type | Best Product | Notes |
|---|---|---|
| Nail holes | Interior filler or spackle | Quick to apply and sand |
| Hairline cracks | Flexible crack filler | Better for minor movement |
| Gaps at trims | Paintable gap filler | Use where wall meets skirting or architraves |
| Larger surface damage | Setting compound or patching system | May need mesh tape or multiple coats |
If you are unsure which product suits plasterboard, fibre cement, timber or masonry, ask for advice at Bunnings, Mitre 10 or your local paint supplier. The right filler will save time and help the repair last longer.
Safety, Moisture And When To Call A Pro
Always use a dust mask and eye protection when sanding. Keep the area ventilated, and follow Safe Work Australia guidance for handling dust and using tools safely. If you find soft, stained or mouldy material, deal with the moisture source first rather than just patching over it. In bathrooms, laundries and other damp areas, repeated cracking can be a sign of moisture or movement that needs proper investigation.
Painting itself is usually a DIY job, but work involving electrical, gas or certain plumbing components must be done by a licensed professional in Australia. If your repair area is around power points, light fittings, gas appliances or plumbing penetrations, switch off power where appropriate and get a licensed tradie if there is any risk or if the defect goes beyond surface patching. For more serious building defects, check local state-based licensing and Fair Trading guidance, and make sure any repair work complies with the National Construction Code.
Once your walls are smooth and primed, the topcoat will go on much more evenly and look far more professional. And if you are comparing renovation advice across the ditch, you can also visit Trade Directory NZ.
If you’d rather hand the prep work to someone experienced, find trusted local painters on Aussie Trade Directory and get your walls ready for a clean, lasting finish.