I had one just like that last week. I hit the bad spots with 3-4 percent using the Ryobi EZ Clean until all the clumps turned white, then downstreamed everything with house wash. Took a Mountain Dew break, gave it all another house wash mix & rinsed everything off a few minutes later. The mortar joints were in bad shape so I could only use minimal pressure. 2540 nozzle on a 2 foot lance worked great for rinsing away all the clumps.
The mortar joints were in bad shape. I let the hot sauce and dwell time do the heavy lifting. Just enough pressure to push the clumps out of the way worked for me.
Strong pre-mix to kill moss, then surface clean depending on joints. You’ll actually do less damage to joints surface cleaning than using a wand. Cobblestones like that always take 3 times as long as concrete to rinse, reason your minimum price should be in the .25-.30 per ft on pricing, at least. Be aware, if a lot of moss, the roots will grow down in joint and if you take it out, you’re going to be breaking out the mortar too. If a sand joint with a lot of moss, sell them on re-sanding before you start.
Or you can just lightly softwash like Jason did, but you’ll need a strong mix.
Yeah, you’ll want 3-4% on that, and the highest GPM you can. Easiest to sell them a resand and seal and just blast it off once you treat it…much bigger check too.
