Is this a common, known technique or did he just come up with it in the spot?<p>I assume not every building can do this, or else the city would run out of water? Or it depends where you live?<p>And at the end of the day, is it just a matter of aesthetics, that your walls don't get stained? Or is it doing other things to preserve value?
Also does he risk his insurance rejecting the claim saying he caused the damage? Also although probably negligible your then making the flooding worse for your neighbors.