The comparison question
The practical question is not whether Masonry salts, efflorescence and spalling is possible. It is which of several routes best explains bubbling paint, peeling finish, powdering plaster, staining or localized surface release at this location and under this trigger.
Candidate pathway A
Use the facet mechanism—How water transports salts and freeze-thaw or crystallization damages masonry surfaces.—as one candidate. Write its predicted timing, location, direction of spread and response to a safe control change.
Candidate pathway B and other lookalikes
Keep active moisture, old coating incompatibility, salt movement, poor preparation, thermal stress and substrate decay visible. A competing cause deserves its own prediction rather than a vague note that it is possible.
Observations that actually separate the candidates
Prefer differences in lag time, event dependence, geometry, direction, operating state and recovery. A generic stain, odor, sound or crack often supports several causes at once and therefore has weak separating power.
False confidence to avoid
Do not count repeated observations of the same non-specific clue as independent confirmation. Do not let the easiest repair define the cause. Cosmetic improvement can reduce visibility without controlling the pathway.
Turn the comparison into a next decision
Choose the next safe observation that produces different expected results for the two leading explanations. If no non-destructive check can separate them, document the uncertainty for a qualified assessment. The source set for this guide includes 4 official records selected for this path. They provide general technical and safety context; they do not determine the condition of a particular house.
Primary references for this topic family
These references ground the general building-science or safety context. They do not diagnose a specific house, replace local requirements or certify a repair.
