A curiosity

I took a break from doing job applications this afternoon to deliver yesterday's leaflets and noticed that in several places along this newish wall the mortar was curling out with moss still attached, something I've never seen before. Has the moss caused the damage, I wonder, and if so how? I know that ivy can take all the moisture out of mortar so that it crumbles, but moss?

One job application in, one deadline missed (I got the dates muddled) and one application I'm part-way through. As I try to match myself to the selection criteria for this one I feel more and more bored and find the applicant becoming more and more boring.

I think I'll go back to googling 'mortar damage'.

Edit: my reliable informant tells me that moss couldn't do this unless the mortar was a bad mix in the first place - probably too much sand/not enough cement.