White spots on roof - lichen?

After soft Washing this roof we were able to kill and remove the moss but all these white spots remained… we thought it was white lichen but I guess not? Anyone have experience with these? They seem to be common out here in the pacific northwest.

What did you use for chems?

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A local surfactant and H. Diluted it was probably around 4-5%

Another sofwashing company believes it’s efflorescense. I’ve never seen efflorescense like this before - but maybe?

Are those cedar shake shingles?

There just looks like a whole lot of organics left, all that blackness. How old was your SH? Did you use a 12v or try to DS/xjet? Any idea what those shingles are made of, and what color they’re supposed to be?

If those are cedar shakes, isnt there an issue with cedar having an occasional reacting with SH where it leaves white spots like this? I forget what it was called.

They are actually concrete tiles. They are dirty because the treatment was done 8 months ago but apparently the white spots never went away where the organic greens did. This is why I think this is efflorescence from the concrete.

Are their a lot of birds in the area? Seriously you don’t usually see efflorescence in spots like that.
Have you talked to the manufacturer?

Sorry for the late reply here - definitely not bird droppings. We tried applying SH on it again with no difference or results. We did a small patch with an efflorescence product which seemed to do more than the SH but still not fully removed it - it just made it fade. Contemplating using Muriatic Acid next time I come across this as I’ve already parted ways with client.