How often do you pressure wash exterior/parking lot of your commercial property?

[Courtney Nguyen]

Hi BP community,

I manage a multi-tenant retail strip (9 units).  The property is fairly new (4 years old).  I am seeing some black spots in sidewalks, curbs, some dirt built up in parking lot so I am thinking it's time to have a power wash on the exterior of the building.  But then I also see some places that have way more mildew, mold, algae built up and look like they never got washed.  It makes me wonder how often do these commercial properties get power washed?  And how do you schedule it so that it gets done without disturbing your tenants?  I am thinking of doing it over the weekend, early in the morning while most tenants are not open yet.  However, it still doesn't quite work out since we have a coffee shop which opens early, everyday.

Any advice, tips, info is greatly appreciated.