There are some key points to note when preparing to paint exterior areas. Using the correct technique and quality paints will result in a painting job that is faster, cheaper and easier to use than alternative methods.

exterior paint preparation boys play next to pool

Filling and patching

Before painting, remove and replace any rotten or decaying timber. Fill any holes and cracks in your exterior surface with a high quality filler such as Selleys® Plasti-Bond Heavy Duty. Apply the filler with a putty knife, overfilling to compensate for shrinkage as it sets. Where movement is likely to occur, use flexible exterior grade filler such as Selleys® No More Gaps® Exterior & Weatherboard.

Masonry and brick

Prep your masonry and brickwork for painting by scraping away any loose paint. Fill holes with an exterior masonry filler, such as Selleys® No More Cracks™ Exterior Brick & Render, using a broad-bladed knife or scraper. Using a brush or rag, roughen the filler before it dries completely to match the texture of the surrounding surface.

Got a larger hole to fill? Use ready mixed filler such as Selleys® Spakfilla® Heavy Duty on large cracks.


If your paintwork is already in good condition, a light but thorough sand should be sufficient.

Any small areas of peeling or cracking can simply be sanded back. Larger holes and defects should be filled and spot primed. If you’re dealing with painted brick or masonry, wash it with a high-pressure cleaner and a stiff bristled brush. For paintwork and wood all that’s needed is general purpose sandpaper. For bare metal, a cloth backed emery paper will last longer and get the job done quickly.

TIP: if you have a lot of sanding to do, consider using a mechanical sander.

Bare timber & nail heads

Before painting, any timber that has been exposed to the elements for more than four weeks should be sanded back to a fresh, new surface. A grey or weathered surface makes an unsound base that promotes peeling and flaking. Simply sand the surface back to remove all greyed timber.

Replace old steel nails with galvanised nails for improved strength and durability. Ensure any nails are punched at least 3mm below the surface, then spot prime and fill holes with a flexible wood filler and sand smooth.

Tannin staining

Some common building timbers contain a natural staining material called tannin. Timber tannins can often break up and carry through to the timber’s surface via moisture in the wood. Cleaning the surface thoroughly and apply an exterior top coat with tannin blocking properties. 

Bare masonry, bricks and cement sheeting

Before painting any porous surfaces like bare masonry and cement, it’s important to remove all loose material with a stiff brush. Next, prime the surface to improve adhesion and durability. We recommend using Dulux 1Step® Acrylic Primer Sealer Undercoat, or Dulux Prepcoat Sealer Binder if your substrate is particularly powdery.

Cement render, concrete bricks and mortar must be allowed to cure for a minimum of four weeks, and concrete for a minimum of 8 weeks, before painting with an acrylic paint. If you plan to use an oil-based paint, even longer is required.

While it takes time, curing your cement is vital. It protects against excessive moisture loss and makes for strong, sturdy foundations by reducing the chance of cracking.

Bare metal

Ferrous metals like wrought iron and steel are prone to rust. Before painting, ensure they are free of rust by sanding or wire brushing the surface and treating with a Rust Remover. Then use Dulux All Metal Primer before applying the topcoat.

Non-ferrous metals like galvanised iron and Zincalume® should never be treated directly with oil based enamel paints. Instead, prime with Dulux All Metal Primer.

As for aluminium, copper, brass and stainless steel, paint will not stick directly to them. Instead, prep the surface by scrubbing with a scouring pad and water before wiping down with a clean rag. Then prime the surface with Dulux All Metal Primer before applying the top coat.

New plastic down pipes and spouting

Plastic down pipes and spouting need a clean surface for paint to stick to. Wipe them down with a cloth dampened with turps, and then lightly sand to provide a sound key for the paint. Immediately before painting, wipe down once more with a water-dampened rag.

Previously painted surfaces

Want to freshen up an existing paint job? Start by testing the paint in several areas. Cut with a sharp knife and press 10cm or so of adhesive tape firmly across the middle of the cut. Remove the tape quickly. If any pieces of paint come with it, you will need to strip the loose paint off before applying the new top coat.


If you need to strip back any existing paint, use a heat gun or a chemical stripper such as Selleys® Kwik Strip Smart. Only need to strip a small area? A manual or drill mounted wire brush or dry scraper should do the trick.

Blistering, flaking and peeling

Blistering, flaking and peeling on wooden surfaces is usually caused by moisture trapped beneath the paint. You’ll find that it almost always happens on the north and west sides of the surface as these areas receive the most sunlight. It’s also common with dark colours that have been applied over old paint.

The first thing to do is remove the source of the moisture. Around windows and doors, look for cracks and seal them. When it comes to walls, the problem may be condensation. Ensure the area has adequate air-flow and consider installing additional vents.

Strip back as much paint as possible then sand the surface smooth and prepare it for a new top coat with Dulux 1 Step® Acrylic Primer Sealer Undercoat.


Australia’s high UV sunlight means that oil based enamel breaks down over time, leaving a chalky or powdery surface. Before repainting, the chalking should be scrubbed off and the adhesion of the old paint tested.


You can remove mould from your exterior surfaces by diluting 1 part household bleach with 3 parts water. Ensure your eyes, skin and clothing are well protected then apply the solution to the mould with a thick scouring pad. Leave it to do its job for 15 minutes then wash with water. Persistent mould growth may require repeated treatments. To avoid the mould returning, be sure to remove any moisture source where possible and prime with Dulux PRECISION® Stain & Mould Blocker.

Acrylics or enamel?

Acrylics are better than oil based enamel for most exterior situations as they retain their colour better and provide a longer lasting, more durable finish. As enamels age they become brittle and chalky, causing surface cracks and flakes.

For all exterior painting we recommend Dulux Weathershield®. It’s backed by the Dulux promise that guarantees a great finish for as long as you live in your house.

In the Australian sun the paint is touch dry in twenty minutes at 25°C and 50% humidity. This means that during the summer months the drying process is accelerated and the chance of flaking increased.

To slow down the drying rate, add Dulux Hot Weather Thinner to the paint at the rate of 50ml per litre. Another good tip for painting in summer is to avoid painting in direct sunlight or onto a hot surface. Follow the shade wherever possible. You can also add up to 5% water to the paint.

Finally – don’t forget about your brushes. Keep two brushes on hand, one in a bucket of water, and alternate between them to stop them drying out.

Zincalume is a registered trade mark of BlueScope Steel Limited.

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