Exterior wall

[Blackhorse5]

Have this coming through white masonry paint. The base of the wall is brown and doesn't have this problem. When scratched it's yellow underneath. Any help gratefully appreciated.

 

[sparkwright]

I am guessing the wall was not cleaned off from moss and algae before painting.

 

[michealangelo]

I am guessing the wall was not cleaned off from moss and algae before painting.

Yep , looks exactly that

 

[Deleted member 265726]

What is the substrate underneath the paint? What was the masonry paint used? Most have a fungicide in them but if the walls were really green they should have been cleaned with a specialist render/brick cleaner or just a diluted bleach solution prior to painting to kill it off. Realise it's a bit late now. If the paint has not adhered properly, it will need to be removed or you can wait until it starts removing itself and then begin the process of removing it, which will make your job easier.