Most exterior cleaning damage we get called out to fix was caused by someone using high pressure on a surface that needed chemistry instead.
Pressure washing
High-pressure water, no real cleaning agent. It works by force. That is the right tool for concrete driveways, sidewalks, and sound masonry — hard, non-porous surfaces that can take it.
It is the wrong tool for anything that can be driven apart by force.
Soft washing
Low pressure, with a cleaning solution doing the actual work. It kills the organic growth rather than blasting it off, which means it stays gone longer.
This is what roofs, siding, painted wood, and older brick need.
The damage you cannot undo
Point a pressure washer at vinyl siding and water goes behind the panels. You will not see it that day. You will see it later, in the wall.
On older mortar, high pressure erodes the joints. On painted surfaces, it strips the paint. On a shingle roof, it removes the granules that the shingle depends on, and takes years off its life in an afternoon.
The short version
If the surface is hard and flat, pressure is usually fine. If it is porous, painted, layered, or has something living on it, it needs soft washing.
When you are not sure, ask before you start. Undoing this is more expensive than doing it right.