What Is Efflorescence?
Efflorescence is dissolved mineral salt left at the surface when water travels through brick, mortar, concrete, or concrete roof tile and evaporates. The white bloom is harmless in itself and common on new masonry as construction moisture leaves. Its diagnostic value is the point: recurring efflorescence means liquid water is repeatedly entering the material, dissolving salts, and migrating out — on a chimney, that typically indicts a failed crown, missing cap, or saturated brick faces needing counter-flashing and sealant attention; on concrete tile, persistent bloom marks tiles staying wet from poor drainage or debris. The freeze-thaw implication matters most: masonry wet enough to effloresce is wet enough to spall when it freezes, so the stain often precedes flaking brick faces and crumbling mortar. Homeowners can test by brushing dry — efflorescence powders off — and by watching whether it returns after rain. Treatment is source-side: fix the water entry (crown, cap, flashing), then clean; sealing over an active source traps the water and worsens spalling.
Important Distinction
Note: Efflorescence dissolves in water and brushes off dry (it is salt); hard white crust that will not brush off is lime carbonation, and white staining on shingles below metal is usually corrosion wash. All three read as 'white stains' and mean different things.
Also Known As
These are the search terms and phrases that commonly refer to this topic, so you can find it however you describe it.
How Efflorescence Relates to Other Topics
The white haze on concrete tile is efflorescence - minerals carried to the surface by evaporating water; on tile it is cosmetic and weathers off, but the same haze on chimney masonry signals water actively moving through the material.
Efflorescence concentrated on the uphill face of a chimney is water telling you where it dams: that face takes the roof's runoff head-on, which is the same reason wide chimneys get crickets built behind them.
Related To Efflorescence
Efflorescence appearing below the counter-flashing line means water is entering the masonry above it - the flashing can be perfectly sound while the chimney crown or brick lets water in behind the whole assembly.
Questions about Efflorescence?
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