Does anyone know what the possible cause for this is...doesn't look like efflorescence to me as it's in the mortar although I'm happy to be corrected on that! It's below a window on a groundfloor flat.
Efflorescence can develop in mortar. It's either that or lime bloom, and the cause in either case is excess water within the wall drying and drawing salts out.
Lime bloom can be dealt with using a hydrochloric acid. Efflorescence needs dry brushing and time, lots of time.
In either case the source of the excess water needs to be removed.
slightly higher up the wall there's signs of remedial pointing.
why not rake out to 25mm, clean out & re-point the wall including the plinth? it would be worth doing esp in a solid wall like yours.
so far, it only seems to have affected the beds & perps - those good old yellow bricks are holding out well.
the green on the plinth means its taking some splash.
Thanks for all the replies. Just for context this is a job I've been asked to have a look at and not my property. I want to go inside and have a look for a possible water leak but the flat is tenanted and they are hard to get hold of. Does it seem likely that the reason for the salts being there is due to the bricks getting wet from some source other than rain? If so, one the source has been found and rectified is it a simple repointing job?
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