How to Prepare Walls for Painting: Professional Checklist
By James Thornton, Perth Painting Services | 11+ years painting Perth homes | Updated 3 October 2026
Quick answer
To prepare walls for painting: clear the room, check for safety hazards, clean the walls, scrape loose paint, fill cracks and holes, sand smooth, remove dust, spot-prime repairs and stains, then mask the edges. Good prep takes longer than painting itself, and it’s the biggest factor in whether your paint looks smooth and lasts.
Key takeaways
- Prep decides the finish. Even premium paint will peel or look patchy over dirty, damaged or glossy walls.
- Clean first, then repair, then sand, then dust off, then prime.
- Older homes can contain lead paint or asbestos. Check before you sand or scrape.
- Spot-prime every patch, or filled areas will show through as dull spots.
- Inspect the walls in good light before the first coat goes on.
What you’ll need
| Item | What it’s for |
|---|---|
| Drop sheets and masking tape | Protecting floors, skirting boards, power points |
| Sugar soap (or mild detergent) and clean cloths or sponge | Cleaning dirt, grease and marks |
| Paint scraper | Removing loose, flaking paint |
| Flexible filling knife and filler | Holes, dents and cracks |
| Flexible gap filler (caulk) and gun | Gaps at cornices, skirting and architraves |
| Sandpaper or sanding block (120–180 grit) | Smoothing filler and glossy surfaces |
| Dust mask, safety glasses, gloves | Protection |
| Stain-blocking primer or undercoat | Sealing patches, stains and bare surfaces |
| Torch or work light | Spotting flaws |
| Ladder or extension pole | Reaching high areas safely |
Before you start: check for lead and asbestos
If your home is older, do this first.
- Lead paint. Homes built before the 1970s may have lead-based paint under later coats. Never dry-sand or scrape suspected lead paint. Use a lead test kit and get advice before disturbing it.
- Asbestos. Australian homes built before the mid-1980s can contain asbestos in fibro sheeting, eaves, textured ceilings and wet-area walls. Don’t sand, scrub or drill suspected asbestos material. The Asbestos Safety and Eradication Agency explains how to identify and manage it.
If you’re unsure, stop and get a professional opinion before you start prepping.
How long does wall prep take?
| Task | Typical time |
|---|---|
| Single bedroom (clean, fill, sand, spot-prime) | A few hours of work, plus drying time |
| Living room or open plan | A day or more |
| Whole house | Often several days |
Fast-drying fillers can be sanded in as little as 30 minutes, but deep repairs need more time and layers. Always follow the product label.
How to prepare walls for painting: 10 steps
Step 1: Clear the room and protect surfaces
Move furniture out or into the centre of the room and cover it. Lay drop sheets over floors, and remove curtains, wall hooks, switch plates and nails. Turn the power off at the switchboard before removing covers from switches or power points. For help with this stage, see how to prepare your home for painters.
Step 2: Inspect the walls in good light
Hold a torch at a shallow angle to the wall. This “raking light” shows dents, bumps, hairline cracks and joins that normal light hides. Mark problem spots with a pencil or sticky dots.
Step 3: Dust and clean
Dust down walls, cornices and skirting boards, including cobwebs. Then wash from top to bottom with sugar soap diluted as the packet directs, using a clean cloth or sponge. Rinse with clean water and let the wall dry completely. Paint and filler won’t bond properly over grease, residue or damp.
Kitchens and bathrooms need the most cleaning, because grease and soap film stop paint sticking.
Step 4: Deal with mould
Black or green spots need treating before anything else. Use a mould-killing wash (or a diluted bleach solution as directed), scrub, rinse and let it dry. Then find and fix the moisture source, such as a leaking pipe, poor ventilation or a roof leak. Painting over mould just hides it for a short time.
Step 5: Scrape off loose and flaking paint
Hold the scraper at about 45 degrees and remove anything that’s loose, bubbling or peeling. Feather the edges of remaining paint so there’s no hard step. Wear a dust mask and safety glasses.
Step 6: Fill holes, cracks and dents
Use pre-mixed filler for small holes and dents. Apply it with a flexible knife, slightly proud of the surface, and fill deep holes in layers, letting each dry. Use flexible gap filler where walls meet cornices, skirting boards and architraves, because those joints move.
Step 7: Sand smooth
When filler is dry, sand the patches flush with a sanding block, working in light, even strokes. Fine sandpaper (around 150–180 grit) suits previously painted walls. Also give glossy walls and trim a light scuff sand so new paint can grip. Don’t press hard, or you’ll make dips.
Step 8: Dust off again
Sanding dust left on the wall causes rough, gritty paint. Wipe with a slightly damp cloth, or vacuum with a brush attachment. Let it dry.
Step 9: Spot-prime or prime
Apply a stain-blocking primer or undercoat to filled patches, stains, bare plaster and any areas you scraped back. Without spot-priming, patches soak up paint differently and show through as dull spots, a problem called “flashing”. If you’re making a dramatic colour change, prime the whole wall (see the priming table below).
Step 10: Mask the edges
Apply painter’s tape along skirting boards, architraves, window frames and fittings. Press the edge down firmly, and remove the tape before the paint fully cures, at a shallow angle, for clean lines.
Finish with a last look under raking light. Anything you can still see now will be obvious once painted.
Prepare different wall surfaces
| Surface | Key prep steps |
|---|---|
| Painted plasterboard | Clean, spot-fill, sand, spot-prime. Scuff glossy areas |
| New (unpainted) plasterboard | Dust off, then prime with a suitable sealer or primer |
| Brick | Scrub with a stiff brush, treat mould and efflorescence (white salt bloom), let dry fully, use a primer suited to masonry |
| Concrete or render | Clean thoroughly, repair cracks, check for dampness, use a masonry primer |
| Wallpapered walls | Remove paper, soften and scrape off glue residue, wash, let dry, fill and prime. Some wallpapers can be painted over, but results vary |
| Timber panelling | Wash, fill, sand back glossy finishes, use a suitable primer and undercoat |
| Previously glossy or oil-based paint | Clean, scuff-sand, and prime with a product made for bonding to glossy surfaces |
Common wall problems and how to fix them
| Problem | What to do |
|---|---|
| Greasy marks (kitchens) | Degrease with sugar soap or detergent, rinse well |
| Water stains | Fix the leak first. Let the area dry, then seal with a stain-blocking primer |
| Nicotine or smoke stains | Wash, then use a stain-blocking primer. Ordinary paint will let stains bleed through |
| Crayon or marker | Clean as much as possible, then seal with a stain-blocking primer |
| Hairline cracks | Fill with flexible filler or gap filler, sand, spot-prime |
| Wide, growing or stair-stepped cracks | Don’t just fill. Get a builder or engineer to check for structural movement |
| Nail pops (plasterboard) | Re-fix the screw or nail, fill, sand, prime |
| Peeling paint | Scrape back to a firm edge, sand, prime, fill the step |
| Bubbling paint | Cut open the bubble, find the cause (moisture or poor adhesion), repair and prime |
| Gritty or textured old patches | Sand smooth, dust off, spot-prime |
Do you need to prime?
| Situation | Prime? |
|---|---|
| Clean, sound walls, same or similar colour | Usually not needed, though spot-prime repairs |
| Filled or patched areas | Yes, spot-prime |
| Bare plaster or new plasterboard | Yes, full coat |
| Stains (water, smoke, grease) | Yes, use a stain-blocking primer |
| Dark to light colour change | Yes, undercoat or tinted primer helps coverage |
| Glossy surfaces | Yes, use a bonding primer after a scuff sand |
Perth-specific prep tips
Fast drying. Perth’s heat and low humidity mean filler, primer and paint dry quickly. That’s convenient, but walls in direct afternoon sun can dry too fast, which causes lap marks. Prep and paint sun-exposed walls in the cooler part of the day where you can.
Seasonal movement. Cracks often appear around door and window corners and where walls meet ceilings. Use flexible gap filler in these spots, because rigid filler can crack again.
Older Perth homes. Character homes in suburbs such as Mount Lawley, North Perth and Leederville often have layers of old paint, plaster repairs and period detail, which means more prep. Check for lead and asbestos first.
Dry-looking walls can still hold moisture. Check bathroom, laundry and external-wall areas for damp before sealing and painting.
Common wall prep mistakes
- Painting over dirt, grease or dust
- Skipping the sand after filling, so the patch shows
- Skipping spot-priming
- Using rigid filler on joints that move
- Painting over mould or damp without fixing the cause
- Sanding or scraping old paint without checking for lead
- Removing tape too late, or too aggressively
- Rushing the dry times between steps
DIY or hire a painter?
DIY prep can save money if the walls are in good condition and you have the time. But prep is the most time-consuming and skilled part of painting, and mistakes show up in the finish. Consider a professional if:
- The home is older and may contain lead or asbestos
- There’s widespread cracking, flaking or damp
- You have high ceilings or stairwells
- You want a flawless finish, or you’re preparing to sell
A professional quote usually includes prep, which is often the biggest part of the labour. For pricing, see our interior house painting cost guide and how much it costs to paint a room in Perth. Professionals also follow the Australian guide to painting buildings, AS/NZS 2311, as a benchmark for preparation. If you decide to hire, read 12 checks to choose a reliable painter in Perth.
Checklist: are your walls ready to paint?
- ☐ Checked for lead and asbestos (older homes)
- ☐ Walls clean, rinsed and completely dry
- ☐ No mould, and the moisture source is fixed
- ☐ Loose and flaking paint removed
- ☐ Holes, cracks and dents filled
- ☐ Gaps at cornices and skirting sealed with flexible filler
- ☐ Filled areas sanded smooth
- ☐ All dust removed
- ☐ Patches, stains and bare areas primed
- ☐ Edges, fittings and floors masked and protected
- ☐ Final check under raking light
What to do next
Once the walls are ready, choose your colour with our guide to interior paint colours in Perth, and plan the timing with how long it takes to paint a house in Perth.
Frequently asked questions
What is the first step in preparing walls for painting?
Clear the room and protect floors and furniture. Then inspect the walls in good light, and check for hazards like lead paint or asbestos in older homes.
Do I need to wash walls before painting?
Yes. Dirt, grease and dust stop paint sticking. Wash with sugar soap or mild detergent, rinse, and let the walls dry fully.
Do I need to sand walls before painting?
Yes, at least lightly. Sand filled patches flush, and scuff-sand glossy surfaces so new paint grips. Remove all dust afterwards.
Do I need to prime walls before painting?
Not always. Spot-prime repairs, stains and bare surfaces, and prime the whole wall for big colour changes or new plasterboard.
How do I fill holes and cracks before painting?
Use filler for holes and dents, applied in layers for deep ones, then sand smooth. Use flexible gap filler at joints that move.
How long should filler dry before sanding?
It depends on the product. Some fast-drying fillers can be sanded in about 30 minutes, but deeper repairs need longer. Follow the label.
How do I get rid of mould before painting?
Treat with a mould-killing wash (or diluted bleach as directed), scrub, rinse and dry. Then fix the cause of the moisture, or the mould will return.
Can I paint over old gloss paint?
Yes, but not directly. Clean it, scuff-sand it, and apply a bonding primer first.
Is it safe to sand old paint?
Not always. Homes built before the 1970s may contain lead paint, and older homes may contain asbestos. Test before sanding and get professional advice if unsure.
How much does professional wall prep cost?
Prep is built into most painting quotes and is often a large share of the labour. See our Perth interior painting cost guide.
Want a professional finish without the prep work?
Perth Painting Services provides interior painting, house painting and residential painting across Perth, including Bayswater, Morley, Balcatta and Joondalup. Our team has 11+ years of experience in thorough surface preparation.
Free quote: Contact us
Phone: 0434 675 004
Email: info@perth-painting-services.com.au
Hours: Mon–Fri 8am–6pm | Sat 9am–2pm | Sun & public holidays closed
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