The number, and why it is not that useful
A quality exterior coating in Sydney generally wants redoing every seven to ten years. That is the honest average and you will see it quoted everywhere.
It is also close to meaningless applied to a specific house, because the same paint on the same building fails at very different rates depending on which wall you are looking at. A sheltered south facing wall can go fifteen years. The west facing wall on the same house might be chalking at six.
So rather than working to a calendar, learn to read the wall.
The four signs it is time
In rough order of how early they appear.
- Chalking. Rub your hand firmly across the wall. If it comes away with a powdery residue, the binder has broken down under UV. This is the earliest reliable sign and it is the one most people never check
- Fading, especially uneven fading between elevations. Strong colours go first, and reds and deep blues fade fastest
- Hairline cracking or crazing in the film itself, which looks like a fine net across the surface. The coating has lost its flexibility
- Flaking, peeling or blistering. By this point water is already getting behind the film and you are no longer just repainting, you are repairing
Why the west wall always goes first
Two reasons, and they compound.
Australian UV is among the most intense in the world, and a west facing wall takes the full afternoon sun at the hottest part of the day. UV breaks down the binder that holds the pigment together, which is what chalking actually is.
Then there is thermal movement. A dark west facing wall in a Sydney summer can reach surface temperatures well above sixty degrees in the afternoon, then drop more than thirty degrees overnight. The coating expands and contracts through that cycle every single day. Eventually it loses flexibility and starts to craze.
North facing walls get the same treatment slightly less severely. South and east elevations have a far easier life.
What shortens it
Coastal salt is the big one. Within about five hundred metres of open surf, expect meaningfully shorter intervals. Salt settles on the wall, dissolves in humidity, soaks in, then crystallises as the wall dries, and those crystals push coatings apart from underneath.
Poor preparation last time is the other. If the previous job painted over chalking or flaking without dealing with it, the new coating was bonded to a failing one from day one, and it will come off at the same rate the old one was already going.
Dark colours shorten it, because of the thermal cycling. And moisture problems shorten it dramatically, whether that is rising damp at the base of a wall, a leaking gutter, or a fence with no capping letting water into the top of the masonry.
Repainting early is cheaper than repainting late
This is the part worth taking away. There is a real difference between repainting a wall that is chalking and repainting one that is flaking.
A chalking wall needs washing, a binding primer and two coats. A flaking wall needs scraping, sanding, filling, spot priming and two coats, and it takes far longer. If water has been getting in behind the film, you may also be repairing render before anything gets painted at all.
Catching it at the chalking stage can be the difference between a straightforward repaint and a job that costs substantially more and takes twice as long. Check your western wall once a year with the back of your hand. It takes ten seconds.