Our house has raised planters built from concrete block, rendered, painted white and capped with slate coping (20mm slate tiles cut to size 150x400).... Problem is that the grout between the slate copings has caused (what I can only describe as) black "run off" marks running down the face of the walls. I assume the black grout used has over time been washing away due to the British weather and stained the walls -- we tried repainting the walls last year but the marks are visible once it's rained a few times.
So -- I'm planning to remove the grout from the coping stones and want to know what the best thing to use is? I've seen tubes of "instant mortar", is there any form of matt silicon or some sort of outdoor caulk that would be better to use? I don't want to re-grout just to have the same problem occur.
So -- I'm planning to remove the grout from the coping stones and want to know what the best thing to use is? I've seen tubes of "instant mortar", is there any form of matt silicon or some sort of outdoor caulk that would be better to use? I don't want to re-grout just to have the same problem occur.
