How to prepare house for painting in Perth is the question that separates a paint job lasting a decade from one that blisters inside twelve months. I have been painting homes across this city for over twenty years. Ninety percent of the result comes from what happens before a brush touches the wall. Here is exactly what needs doing, in the right order, for a finish that holds up to the sun, the heat, and the winter damp.
It starts with accepting what prep really means
The UV index in WA is among the highest in Australia. Summer heat pushes surface temperatures on a north-facing wall past sixty degrees. Winter brings driving rain and morning humidity that sits around eighty percent. Paint on a poorly prepared surface does not stand a chance.
Last summer we took over a repaint in Dalkeith where the previous painter had rolled straight onto walls he wiped with a damp cloth. Six months later the north elevation was peeling in sheets. The paint was fine. The prep was not.
If you are not prepared to spend roughly sixty percent of your project time on preparation, you are not ready to paint. That ratio separates professional work from everything else.
Step one: assess what you are working with
Walk around your property before you buy a drop of paint. Look at every surface critically. Is the existing paint intact or is it flaking and bubbling in patches? Are there chalky deposits on the north-facing brickwork? That is UV degradation and needs stabilising before anything sticks to it.
Check for moisture problems. In older suburbs like Mount Lawley and Bayswater, rising damp in weatherboard and brick homes is common. Paint over a damp wall and it bubbles every time. The moisture source needs fixing first.
Look for plaster cracks, gaps around window frames, holes from old picture hooks. Every one shows through fresh paint. The light in WA is sharp and catches every imperfection.
If you are not confident assessing the condition yourself, professional house painters in Perth can inspect as part of a free quote. We usually spot three or four issues homeowners overlooked.
Step two: wash everything properly
Sounds basic. It is also the step most DIY painters skip. Walls collect a surprising amount of grime. Kitchen grease, dust from the easterly winds, spiderwebs in the eaves, fine red dust from the hills. Paint will not grip dirt.
Sugar soap and warm water. Work from the bottom up so dirty water does not run over clean wall and leave streaks. Rinse with clean water and let the walls dry at least 24 hours. In winter, give it 48. Riversides suburbs like Como stay damp longer and drying times blow out noticeably.
For exteriors, a pressure washer on low setting. Too much pressure damages the paint and the timber underneath. Hold the nozzle at arm's length and let the water do the work. South-facing walls that stay damp longer and grow moss need extra attention.
Step three: scrape, sand, and fill
Take a broad scraper and remove every flake of loose paint. Paint that looks stuck on but lifts at the edge needs to come off. Leave it and the new coat lifts too. We generally find more loose paint than homeowners expect, especially on west-facing elevations that cop the afternoon sun.
After scraping, sand everything. You do not need to strip down to bare timber everywhere, just knock down the rough edges and give the new paint a surface to grip. 120-grit for most surfaces, 80-grit for stubborn areas. Wear a mask. Even paint without lead creates dust you do not want in your lungs.
Fill every hole, crack, and dent. Builders' bog or a flexible gap-filler for timber. For plaster, use a setting-type compound that does not shrink. Let it dry completely, then sand smooth. If you can feel a bump with your finger, you will see it after painting.
For exterior timber, check for rot. Push a screwdriver into the timber near window sills, door frames, and verandah posts. If it sinks in, the timber is compromised. Cut it out and replace it before painting. Rot keeps spreading under the paint regardless of what topcoat you use.
Step four: prime everything bare
Bare timber, bare plaster, bare metal. They all need primer. Primer seals the surface, provides adhesion, and stops the topcoat soaking in unevenly.
Use the right primer for the substrate. Timber needs an oil-based or water-based exterior-grade primer depending on the topcoat system. Plaster needs a high-build interior primer that seals the porous surface. Metal gutters, downpipes, and window frames need a rust-inhibitive primer. Using interior-grade primer on exterior surfaces is a guaranteed failure in the WA climate.
One detail most people miss: if you are painting a dark colour with a light one, get a tinted primer. A grey primer under white topcoat covers better than white primer does. Most paint suppliers can tint the primer for you at no extra cost.
Step five: the critical trade checklist — pre-paint curing and moisture windows
One of the easiest ways to spot an amateur job is checking how long they waited after a repair before painting. Different materials have strict curing windows. Paint over them too soon and residual chemicals or moisture destroy the adhesive bond within weeks.
| Material / Repair Type | Minimum Curing Window | What Goes Wrong If You Rush | How We Verify It On Site |
|---|---|---|---|
| New sand-finish render | 28 days | High alkalinity causes alkali burn, destroying paint binders and bleaching colours | Digital pH pen test must read below pH 9 |
| Fresh Gyprock plaster patches | 24 to 48 hours | Trapped moisture causes localised bubbling and joint tape lifting | Pinless moisture meter must read below 12% |
| Timber builders' bog repairs | 2 to 4 hours | Chemical exothermic reaction releases gasses, creating micro-pinholes in the topcoat | Fingernail indentation test. If it leaves a mark, it is still outgassing |
| Fresh concrete plinths or slabs | 28 days | Hydrostatic pressure forces ground moisture upward, shearing the paint film off | Plastic sheet tape-down test to check for condensation overnight |
Step six: dealing with substrate deficiencies — efflorescence, chalking, and flashing
When prepping an older property, you are rarely dealing with a clean canvas. Decades of environmental exposure create specific problems that need treating during prep, or they show straight through the new paint.
Efflorescence
Looks like a white powdery crust on brickwork and retaining walls. Common in riverside pockets where groundwater carries dissolved salts through the masonry. Paint over it and the salt crystals keep growing, tearing the new paint film off.
Washing with water does not work. It dissolves the salt back into the brick and it returns. Dry-brush the crystals off with a stiff wire brush. Treat the area with a mild acid wash to neutralise the salts. Rinse, let it dry completely, then seal with an alkali-resistant binding primer before any topcoat touches it.
Chalking
Run your hand across a north-facing rendered wall that has not been painted in seven years. If your palm comes away looking like you dusted chalk off a blackboard, that is chalking. The UV has cooked the acrylic binders, leaving loose, unbound pigment dust.
New paint cannot stick to dust. If you topcoat over it, the new layer is just sitting on a loose powder and peels within a single summer. We see this constantly on properties along the coast in Scarborough and Cottesloe where the UV and salt spray accelerate the breakdown. The fix is pressure cleaning with a heavy-duty sugar soap solution, letting it dry, then applying a penetrative masonry sealer to lock down the remaining particles before painting.
Flashing
Flashing is when the finished job looks patchy. Glossy in some areas, flat in others. It happens because porous surfaces like raw plaster patches or bare timber absorb the liquid binders out of the topcoat unevenly.
The solution is straightforward. Every spot where you scraped back to bare substrate or applied filler needs a uniform spot-priming coat. This levels out the porosity across the entire wall so the topcoats dry evenly from edge to edge. Skip it and the patch shows through every time.
Step seven: protect everything you do not want painted
Masking tape and drop sheets. Windows, door handles, light switches, power points, floors, skirting boards. Anything not getting painted needs covering.
Use proper painter's tape. Frog Tape or equivalent. The cheap stuff bleeds paint underneath or leaves adhesive residue. For floors, canvas drop sheets. Plastic is slippery and does not absorb spills. Canvas stays put and catches drips.
For exterior work, protect the garden. Paint mist drifts in the breeze and settles on leaves. Cover shrubs and garden beds. Move pots away. Water the lawn before starting. Wet grass does not absorb paint mist as readily as dry grass.
When you hire interior house painting services, all this protection is included. Commercial-grade masking systems and floor protection that covers more area in less time than anything at the hardware store.
Step eight: check the weather, then check it again
For exterior work in WA, you need three consecutive days of dry weather. Not two. Three. Morning dew settles early in riverside suburbs and paint needs to dry before the temperature drops at night. We generally avoid painting in July and August unless there is a clear five-day dry window in the forecast.
For interior work, avoid painting when humidity sits above 75 percent. That rules out many winter mornings. Paint in high humidity dries slowly and can develop a cloudy finish called blooming. Check the BOM forecast before you start. It takes thirty seconds and saves a world of trouble.
Temperature matters too. Do not paint when the surface is below ten degrees or above forty. In summer, north-facing walls can be too hot by 10 a.m. Start early, finish by midday on the hot side, and work around the house as the sun moves.
How much does professional preparation cost?
If you are weighing up whether to hire a painter, you want to know what the prep component adds. For a detailed breakdown by house size and surface type, see our Perth painting cost guide. The short answer: expect preparation to represent roughly sixty percent of the total quote, because that is where the time and skill goes.
For comparison, read our guide on how long painting takes. It explains why a full exterior repaint runs five to seven days when three of those are just preparation.
Why proper prep saves you money long term
A cheap job that skips prep costs more over the long run. If the surface is not prepared properly, paint fails early. You repaint in three years instead of ten. Labour, materials, disposal. You pay for everything twice. The total cost over a decade can easily hit triple what a single properly done job would have cost.
The homeowners who save the most are the ones who do not cut corners on prep. They clean thoroughly, scrape thoroughly, prime thoroughly, and wait for the right weather. Then they paint once and forget about it for the better part of a decade.
Frequently asked questions
Should I wash walls with sugar soap or TSP?
Sugar soap works for most situations. TSP is stronger and needed for kitchens with heavy grease buildup or exterior walls near a barbecue area. Wear gloves with TSP. It is caustic.
Do I need to sand between coats of paint?
Yes, lightly. A quick sand with 240-grit paper between primer and first coat, and between first and second coats, knocks off dust nibs and gives the next layer something to grip. Small step, visible difference.
Can I prep in winter?
Absolutely. Scraping, sanding, filling, masking. All of that works fine in cooler weather. Just leave the actual painting for a stretch of dry days. Prep in June. Paint in July. That is a realistic winter schedule for most of the metro area.
How do I know if my prep is good enough?
Run your hand over every surface after sanding. It should feel smooth. Look at the walls from an angle with a bright light. Every bump and hollow shows. Fix them before you paint. Once the paint is on, it is too late.
If all of this sounds like more than you want to take on, that is fair. Plenty of homeowners leave it to the pros. Request a free painting quote and we will handle every step from the first scrape to the final coat. Inspect, prep, prime, paint. A finished result guaranteed.