Staining on white rendered wall from stone slabs

[GregH911]

Hi All - Bought a house with lovely white painted rendered garden walls with York stone caps. Every cement joint between the stone caps bleeds horrible dirty brown stains down the walls. How do I stop this from happening? Repainting lasts a month, if that. As you can see, these walls have fence panels in between the pillars - 14 in total and all the same size so you can see the size of my problem. Painting both sides of the wall takes an absolute age. Photo attached

Is my only solution to knock the stone off and render the tops?

 

[Alastairreid]

Form a drip bead on the underside of the coping stones by either using a grinder or a bead of silicone.

 

[KenGMac]

GregH911, good evening.

Your posted image is only accessed on your profile page, it does not appear in your poet?

Having found the image, how much overhang is there on the coping stones and am i correct the overhanging edge is "rounded"?44

Ken

 

[foxhole]

You could give the stone a coat of water repellent which might stop the colour bleeding.