Having these green coloured moss/mildew growing on outdoor painted wall in a couple of location. what is cheap chemical to kill these thing (probably need a few litres of stuff).
if I just paint over, guess the green moss will grow back, so want to get rid of it first.

You might want to read up this article for some insight on what you can do next. Some paint companies do have paint solutions specifically targeting mould or mildew but what's important is surface treatment that prevents rainwater infiltration like Mapei siloxane based masonry treatment stuff used to preserve old architecturally significant sites.

This post has been edited by halcyon27: Jan 30 2018, 08:16 AM

Clorox + pressured washer.