I can't see the photo either, but I wonder whether it's a lovely lichen rather than a fungus problem? People do confuse the two, but a lichen's a harmless symbiotic relationship between a fungus and an algae that have teamed up to survive in extreme environments.
If so, it's a good sign for your air quality, as they don't like air pollution.
Here's the Natural History Museum's lichen info page http://www.nhm.ac.uk/nature-online/life/plants-fungi/lichens/
And here's their ID guide http://www.nhm.ac.uk/nature-online/life/plants-fungi/lichen-id-guide/index.dsml