Exterior recurring water stains on paint

[JT101]

Hi

Rain water is running off the top tiled surface of this terrace, and carrying any dirt etc with it, and then running down the white painted face as you can see in the photo, leaving stains.

It can't be jet washed off. Can anyone give any suggestions of some sort of paint or thin coating which is washable and repels dirt. Someone suggested chlorinated rubber coating, but this is semi gloss, I'd prefer matt.

Many thanks

james

 

[dcdec]

Why isn't the water being collected by the guttering? (no picture)

There are self cleaning masonary paints, they work by chalking, i know johnstones do one and sure most manufacturers do. Wont completely solve the problem though as its dirty water.