Since you've tried different solutions to no avail, it may be time to bring in a power washer. It should "blast" the mold away. You can probably rent one for a few hours and get the job done once and for all. Then treat the wall with mix of bleach/water to help it from coming back right away.
Every time I clean my mirrors, they end up having tons of streaks and almost look worse than before I started. What could I use to clean them that won't leave streaks...
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I recently used Wet & Forget on some wood siding and haven't seen results, yet. I sprayed it on the house about a month ago and wanted to see if I should give it ...
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My question as I watched these grandparents was always, "Why are you sweeping your yards, and why is there no grass around your house?" We have grass around ours.
Since you've tried different solutions to no avail, it may be time to bring in a power washer. It should "blast" the mold away. You can probably rent one for a few hours and get the job done once and for all. Then treat the wall with mix of bleach/water to help it from coming back right away.
You may not be allowing the formula enough time to remove the moss, and this is moss not mold.
http://homeguides.sfgate.com/kill-moss-landscaping-walls-28693.html
You could always try Wet and Forget. My friends swear by it.
wet and forget is the safest route to go