A masonry chimney is leaning away from the house wall. What does an inspector report?

A masonry chimney is a heavy, slender stack of units held together by mortar and usually founded on its own footing. When it leans away from the wall, the most common causes are footing settlement, frost heave, or long-term mortar deterioration that lets the stack rack — all of which are below or inside the assembly and invisible from the outside. Two hazards follow. The structural one is collapse, and a chimney is one of the few building elements that can fall on people. The functional one is that a leaning stack opens joints in the flue, which lets combustion gases escape into the building. Because the cause is concealed and the consequence is severe, the finding is reported as observed and referred for evaluation, with the appliances served treated as not usable until that evaluation happens.

The inspector reports what is observable — that the chimney leans — and that the condition warrants evaluation before the chimney is used. The cause is below grade or inside the masonry and cannot be determined visually, while the consequences include collapse and flue gas leakage.

Masonry chimneys bear on their own footings and rely on mortar joints for stability. Home inspectors report observable conditions such as lean, cracking, spalling and deteriorated crowns, and refer causes that lie below grade or within the assembly to qualified specialists.

Report the Lean, Refer the Cause. You can see that it moved; you cannot see why. Say the first, hand over the second.

Note whether appliances vent into the chimney. If they do, the recommendation should include not using them until the chimney is evaluated.

• •Naming a concealed cause the inspection cannot establish
• •Treating torn flashing as the cause rather than a symptom
• •Reporting the lean without addressing the appliances that vent through it