When exterior paint starts to flake on a coastal Perth home, the paint itself is rarely the reason.
Usually, it is due to substrate contamination that high-end specialist teams like Perth City Painters have to strip back and decontaminate before a fresh coat of paint can be applied.
New paint cannot magically restore a crumbling foundation. It’s like trying to put a band aid on a snapped femur.
If the underlying render is sandy or detached from the brickwork then the new coating essentially acts as a sail, catching the wind until it eventually pulls the surface away from the wall.
Why coastal walls sound hollow
There is a concept called drummy render, this means the substate has de-bonded. This happens when the bond between the plaster and the masonry fails which creates an air pocket.
You can find this by tapping the surface of your walls. If it sounds hollow like a drum it most likely means the render is no longer structurally sound and will eventually blow off the wall.
Because this gap exists, moisture becomes trapped behind the paint film. The Western Australian sun then heats this moisture, turning it into vapour that expands and forces the paint to bubble and peel.
Its like a little science experiment happening on your wall.
The chemical impact of the Fremantle Doctor
Living near the ocean brings constant salty air. Every afternoon when the Fremantle Doctor blows through leaving behind a fresh layer of salt.
This salt penetrates the pores of the masonry and undergoes a process called efflorescence. As the mineral deposits dry they crystallise and expand with enough force to snap the internal bonds of the cement.
These seemingly harmless little crystals will turn your solid render into sand. When white powder appears on a wall it is a sign that the masonry is being destroyed from the inside out by salt movement.
Identifying Surface Rot
- Hollow sounds when tapping indicate that the render has detached from the brickwork.
- White powdery fur on the surface signals active salt destruction of the masonry.
- Vertical splits in the render serve as the primary entry points for water ingress.
- Crumbly render at the base of a wall is a sign of active rising damp.
The risk of paint only quotes
You might get a great looking quote but reading the details of the quote is important. If they have just quoted you for a fresh coat of paint, they are avoiding arguably the most important part of the job.
If a scope of work does not include mechanical grinding or deep decontamination, the project is likely to fail.
A cheap contractor will often paint directly over dirt and salt crust. They might bog up cracks with rigid interior fillers that cannot handle the thermal movement of a Perth summer.
Without this flexibility the new finish will suffer from flashing. This means every little patch work will be visible through the top coat, not the best look.
The technical process of restoration
Professional restoration requires a grinder rather than just a brush. Failing render must be ground back to a solid, fresh surface to allow the new coating to bond properly.
On many Dalkeith or City Beach projects, large sections of south facing walls must be stripped. This is because the render has become too sandy to hold a primer.
Once the loose material is removed, the wall must be decontaminated. Commercial high pressure cleaners are used to strip away salt crust and old chalky paint residue.
If you paint over dusty or sandy old paint, you’re simply asking for it to look terrible and not last.
Managing thermal shock
The trend for dark charcoals and deep greys in Perth puts stress on masonry. Darker colours absorb solar energy which leads to extreme surface temperatures.
This heat causes the render to expand rapidly which is thermal shock. This shock creates tiny spiderweb cracks that may not be noticeable but allows water to seep in.
Solar reflective coatings are the professional solution for these darker colours which reflects the infrared spectrum, keeping the walls cooler and preventing heat related cracking.
Key Takeaways
- Mechanical grinding is required to remove failing render before painting.
- High pressure washing is the only effective way to neutralise salt contamination.
- Flexible membranes are essential to accommodate the thermal movement of Perth homes.
- Solar reflective paints protect dark coloured render from thermal shock and cracking.
Assessing structural integrity
Property owners should not wait for a winter storm to show you where the cracks are. By the time the water reaches inside the internal damage has been done.
A professional moisture analysis and tap test can determine the state of your render. This can decide if you need a full restoration or a simple refresh.