UPDATE: EXPERT OPINION FROM BILL ROSEGreen Building Advisor’s Technical Director, Peter Yost, went to the rising damp master, BIll Rose, to try to solve this once and for all. Bill is the author of Water in Buildings — the definitive book about how water interacts with buildings.Bill said several interesting things about this photo:1. Usually, a pattern of distress makes you want to draw an arrow to the center of the distress — in this case the “waist.”2. I compare it [rising damp] to paper chromatography, a neat way to separate constituents of solutions. Wherever rising damp occurs from water below, the top level is usually some white, easily-transported salts, then lower are some brown stains and at the lowest level is the distress to the brick or stone.3. One approach I use is to imagine the early stages of this distress. I could picture a ring around the parged and painted chimney where peeling begins and flakes off with pieces of brick. At that early stage there would be no doubt but that something (mortar, ash, rubble) filled to that level at the inside.4. It’s pretty unlikely that there is a concrete floor underneath this 1870s chimney. So while it may appear as though the chimney is perched on dry ground, it probably is wicking quite a bit of water up and out of the soil over the years.5. Basically, I don’t know [referring to the interesting shape]. Good one. Somebody keep a big dog in the basement who liked to scratch his side?So, it seems as though we understand that the degradation of the brick is from rising damp but everyone is still pleasingly puzzled by the shape. Thanks all around — and Chris, it sure seems as though you got your money’s worth on this one!Read the whole discussion in the Q&A discussion forum.Further ResourcesEfflorescence ExplainedIn a recent podcast, Joe Lstiburek’s describes how groundwater and salt break down brick, concrete, and mortar . In a recent discussion from our Q&A forum , Chris Ermides tries to determine what caused severe deterioration of a brick column in the basement of his Victorian home. Chris knows that his basement could use some moisture remediation, but he is puzzled that none of the nearby brick walls have similar signs of decay. Fortunately, the chimney that the column once supported is long gone, and the load of the adjacent beams rests comfortably on lally columns, but Chris is still determined to solve this mystery.Michael Maines tells Chris that either basement-dwelling livestock used the efflorescing minerals in the column as a salt lick (JK), or we’re seeing a phenomenon called “rising damp.” The whitewash on the bricks above is actually one way of dealing with it.Michael Chandler thinks the water that caused the spalling may have entered through the old chimney due to a poorly maintained cap. Michael suggests that the epicenter of the damage may be where the bottom flue tile, or some other obstruction, held the water until it worked its way through the brick.James Morgan doubts that rising damp would occur so high above the ground (especially since the foundation walls don’t show similar deterioration). He agrees with Michael Chandler that water trapped in the old chimney may have been the culprit — possibly from a blocked ash cleanout that has since been filled in. James goes out on a limb to suggest a third scenario: perhaps someone started to demolish the old chimney base but had second thoughts.I also pointed Chris to Joe Lstiburek’s recent Building Science podcast on efflorescence .