Despite what Shannon Lush tells us, sometimes the best cleaner for external surfaces is a high pressure cleaner.
What pressure do you need?
The optimum is around 3000 PSI. When you get much below this you don’t get much efficacy – and this generally refers to electric units. So you really need a powered unit. They start at about 2000PSI and the sky’s the limit, although once you get above about 3000PSI the costs start to escalate dramatically.
But you don’t want to go much above 3000 anyway, as once you get around 3500 PSI you start poking holes in mortar – around 4000 you start poking holes in bricks and cement.
Here in Australia the best value for money unit I have seen is a Ryobi from Bunnings. It’s a 3200 PSI unit and costs around $700. Best of all it comes with a 2 year replacement warranty.
A word of advice, however. The cheaper units (like the Ryobi) are direct drive units. this means that when the engine is running it’s constantly pushing water through. If the trigger is closed, then the entire unit is pressurised and the pump can be damaged. So where possible, keep the trigger open and water squirting when the engine is running