2019 semi-detached with saturated back lot (measurable & visible saturation in the roughcast on back & side foundation wall) Noticed effloresence in the mutual concrete block wall in the attic. Since concrete can support capillary action up to 10 km(!!) , I originally thought that the effloresence in the attic was due to water exposure prior to installation of the roof (no signs of leakage in the roof) but once I thought about it and looked up the capillary potential along with the ground saturation, alarm bells went off. I already recommended water management of the lot. NO noticeable humidity in the basement, no measurable humidity in walls, common wall. (all covered with finishing materials). Any thoughts what would be the best recommendation in terms of further investigation & by whom? (And yes…recommendation already made for leaning retainment wall for those inclined to mention it…pun intended)
Any photos?
Did the CMU block have a painted exterior?
Photos posted (CMU… common mutual ?) Foundation wall is poured concrete, the common mutual wall is concrete blocks.
CMU = Concrete Masonry Units = your concrete blocks.
What’s above the roof line? Does the CMU block extend past the roof covering such as pictured below?
I’ll throw a dart at the board…You are in a very cold zone. Could excessive condensation be a source of moisture?
From here it looks like efflorescence possibly caused by block wall cavity not sealed at upper ceiling area. Warm air movement inside block wall condensing in cold attic and also warm air leakage in attic resulting in possible ice damming in winter.
David A. Andersen & Assoc. 
Give me a reason to get out of this heat wave! 