Fresh paint will not hide a rough patch, a greasy wall or a crack that is still moving. In fact, the better the paint sheen, the more it highlights every flaw underneath. Knowing how to prepare walls before painting is what separates a quick cover-up from a clean, durable finish that looks right in daylight as well as at night.
For small, sound walls, preparation is a job many homeowners can manage with care. But if the wall is badly damaged, uneven, damp or covered in recurring cracks, painting over it is usually money wasted. The surface needs to be repaired properly first.
Start by checking the whole wall
Do not begin with a paintbrush. Walk through the room with the lights on and look across each wall from an angle. Side light shows dents, raised patches, plaster joins and uneven repairs that can disappear when viewed straight on.
Look for cracks around doors and windows, nail holes, peeling paint, water stains, loose plaster, mould and soft areas. Run your hand over questionable sections. A wall should feel firm, dry and stable before it is painted.
Hairline cracks in plaster are common, especially in older homes and around openings. They may only need proper filling and sanding. Wider cracks, cracks that keep returning, or cracks paired with sticking doors or ceiling movement can point to movement behind the surface. Those need a closer look before any finishing work starts.
Water stains are another issue not to ignore. Find and fix the source first, whether it is a roof leak, plumbing problem, condensation or external water entry. A stain-blocking primer can stop old marks bleeding through paint, but it cannot solve active moisture.
Clear the room and protect what stays
Preparation gets dusty and messy before it gets tidy. Move furniture out where possible. Cover larger items that must remain in the room, then protect floors with drop sheets. Remove wall hooks, picture frames, switch plate covers and vent covers where safe to do so.
Mask skirting boards, window frames, door trims and fittings with quality painter’s tape. Press the tape down firmly along the edge so paint cannot creep underneath. Cheap tape can tear, lift old paint or leave adhesive behind, so it is not always the saving it appears to be.
If you are working near power points or switches, turn off the power at the board before removing covers. If you are unsure, leave electrical fittings alone and paint carefully around them.
Scrape off anything loose
Paint needs a solid surface to grip. If old paint is peeling, bubbling, flaking or chalky, remove all loose material before filling or priming. Use a paint scraper with a steady hand and avoid gouging the plasterboard or plaster below.
Feather the edge where sound paint meets the exposed area. This means sanding the edge until it tapers smoothly rather than leaving a noticeable ridge. If you can feel a hard edge with your fingertips, there is a good chance you will see it after painting.
Be careful in older properties. Paint applied before the 1970s may contain lead. Do not dry sand or scrape suspected lead paint without taking the right precautions. Professional assessment and controlled removal are the safer option.
Repair holes, cracks and damaged plaster
This is the part that has the biggest effect on the final result. Small nail holes and shallow dents can be filled with a suitable patching compound. Apply it in thin layers with a broad filling blade, allowing each layer to dry before adding more. Overfilling is fine, as long as the excess can be sanded back smoothly.
For cracks, open the crack slightly with a scraper or utility knife to remove weak edges, then clean out dust before applying filler. A simple smear over the top often cracks again because it has not bonded into the gap.
Larger holes, damaged plasterboard corners and failed joins need more than standard filler. They may require a plasterboard patch, joint tape, base coat and finishing coat. The repair must be built out and feathered wide enough to blend into the surrounding wall.
A patch can look flat when you stand directly in front of it but still show as a hump after paint goes on. This is why broad feathering matters. The bigger the repair, the wider the area that usually needs to be skimmed and sanded.
When a repair should be left to a tradie
Call in a professional plasterer or painter when there are multiple cracks, water-damaged sheets, sagging sections, recurring cornice gaps, large holes or walls that need a Level 5 finish. These jobs are not just about making damage disappear. They are about creating a stable, even surface that will hold up after the room is back in use.
For renovation plaster repairs and patch-and-paint work, BIDU Tradies can handle the surface repair and painting as one job. That avoids the usual handover problem where one contractor repairs the wall and another has to work around an uneven finish.
Sand for a flat surface, not just a smooth feel
Once filler is fully dry, sand it until the repair blends into the wall. Start with a medium-fine grit where needed, then use a finer grit to remove scratches. A sanding block or pole sander helps keep broad areas flat. Sanding only with folded paper and fingertips can create dips around the patch.
Do not sand plasterboard paper aggressively. If you damage or fuzz the face paper, seal it with the right primer before painting. Otherwise, moisture from the paint can cause raised fibres or bubbling.
Use a work light held close to the wall, or look along the wall from the side. This simple check reveals imperfections better than staring at the repair head-on. Mark any low spots or ridges, fill again if necessary, and repeat the process. Two careful rounds of filling and sanding often look far better than one rushed attempt.
Wear a dust mask and safety glasses while sanding. Keep doors shut where possible, and vacuum dust rather than sweeping it around the room.
Clean the walls before primer or paint
Sanding dust, cooking residue, fingerprints and cleaning-product residue all affect paint adhesion. Vacuum the walls with a soft brush attachment, including skirting edges and corners. Then wipe the surface with a clean, damp microfibre cloth and allow it to dry completely.
In kitchens, laundries, entryways and around light switches, use sugar soap or a suitable wall cleaner to cut through grease. Follow the product instructions and wipe away any residue with clean water if required. Paint on a greasy wall may look fine for a while, then peel or develop uneven sheen.
Mould must be treated before painting. Wear gloves, improve ventilation and use a suitable mould treatment. More importantly, address the moisture or ventilation issue that allowed it to form. Painting over live mould only hides it for a short time.
Prime the areas that need it
Primer is not always required over sound, previously painted walls when you are using a quality paint system. It is necessary, however, over fresh plaster, plasterboard repairs, bare timber, exposed paper, stain-affected areas and major colour changes.
Spot priming small patches can work with low-sheen paints, but it may leave flashing – areas that reflect light differently from the rest of the wall. If there are many repairs or the wall has mixed surfaces, priming the entire wall is usually the cleaner choice.
Use a stain-blocking primer for water marks, smoke stains, tannin bleed or heavy marker stains. Use a plasterboard or acrylic primer on new plaster repairs. The right primer gives the topcoat an even surface to bond to, which improves both colour consistency and durability.
Check the conditions before you paint
Even a perfectly prepared wall can disappoint if paint is applied in poor conditions. Avoid painting when the room is very cold, excessively humid or poorly ventilated. Moisture slows drying and can affect how the coating cures. On hot days, direct sun can make paint dry too quickly and leave lap marks.
Stir paint thoroughly, use clean rollers and brushes, and keep a wet edge as you work. Cut in one section and roll it while the edges are still wet rather than cutting in the entire room first. Preparation gets the wall ready, but good application is what protects that work.
Before opening the paint tin, run your hand and a side light across the wall one last time. If it feels clean, dry, firm and even, you have given the paint the surface it needs – and the finished room will show the difference every day.
