Walls – this white powder on the walls and around the plumbing


We have a bathroom in a detached structure from our house. We purchased it and have not used this for 6 months.

I just noticed this powder on the walls and I touched some of it on the wall and it just crumbled like baby powder.

It is also on an adjacent wall. There's also white stuff around a hole in the ceiling.

It is also under the sink…around the pipe.

Note this powdery material has build up on the wall so that it is 1/2" or so thick.

I don't know what all of this stuff is and whether it's the same substance in other places in this bathroom.

wall with white powder
ceiling - not directly above wall
under sink opposite wall

Best Answer

Efflorescence! Efflorescence is a crystaline deposit of water-soluble salts on surfaces of masonry, stucco or concrete. Water brings these salts to/toward the surface and then the water evaporates leaving behind the crystaline deposit.

Note: If one has efflorescence on the surface, one can count on having similar deposits just below the surface, too. These sub-surface deposits tend to cause crumbling of the masonry, stucco, or concrete structure.

The presence of mineral deposits on water pipes indicates one of three things:

1) there's a pin-hole in the pipe through which water is penetrating and evaporating to leave behind calcium (and other minerals) behind,

2) water is leaking from a fitting and leaving behind deposits, at the lowest point of moisture travel, before dripping or evaporating,

3) water is carrying minerals from an adjacent wall, ceiling, etc.; which runs down the pipe and leaves behind deposits, from the lowest point of moisture travel, before dripping or evaporating