Efflorescence Question

[inspectorwill]

I need a little education in building science. My understanding of efflorescence is that several factors are involved for the occurrence: soluble salts in concrete, moisture to dissolve the salts and hydrostatic pressure that pushes the salts to the surface of the concrete.

In this 45 year old apartment complex, the walls are finished with plaster and there is efflorescence at various interior walls, mostly bathrooms and kitchens. I can understand the presence on exterior walls but the interior walls puzzles me. There are no signs of plumbing or roof leaks in these areas. Can a high interior moisture level draw the efflorescence to the surface without the usual hydrostatic pressure we see that pushes the salts to the surface at say foundation walls or slabs? I have attached photo of the interior wall beneath a sink.

[Jim Katen]

Hydrostatic pressure isn't necessary. I see efflorescence as a result of capillary water movement all the time.

[mgbinspect]

Richmond, VA has a ton of homes ranging between the mid 1800s and early 1900s with plaster walls and ceilings over wood lath. Any time moisture intrudes for a long period of time through plaster, efflorescence is the end result. I can't think of a time I observed it being the result of high humidity. It is typically a roofing/flashing issue or missing mortar in solid masonry walls.

[BADAIR]

elementary explanation

water in vapor moves from warm toward cool

think cold adult beverage on a warm summer day where is the condensate?

outside of the adult beverage container

i'd imagine where you're at, warm coastal=moist warm outside, dry cool=air-conditioned inside

capillary transfer would deposit and dry on the interior

air leakage, absence or breeches in vapor barrier might be the causative source

not nice to install building materials incorrectly, argue with mother nature or try to combat physical laws