What caused my brick porch pier to lean like that?

Posted by in Masonry, Soil Issues | January 20, 2014

porch pier lean

I don’t know how many leaning porch piers we have evaluated, but I can say – “a lot!”

Leaning porch piers are usually noticed by the tenant or owner of the property after a strong wind storm, a vehicle impact of the porch or dwelling, a nearby explosion, etc.  It is then usually proposed that the lean is due to the recent catastrophic event.  In some cases that is true and the leaning pier will exhibit clean, sharp-edged cracking and/or separations; clean, sharp-edged impact marks; or some other accompanying damage that exhibits physical evidence of being recent.

However, many times the leaning has been progressive and due to a more common damage producing mechanism, differential settlement.  That is, one portion or side of the footing of the pier has dropped more than another.  This is similar to the uneven sinking one notices when a four-legged kitchen chair or a step ladder are set on the soft earth in the backyard and the weight of the user is applied.  One side invariably sinking into the ground more than another and the chair or ladder are no longer level.

Just as the weight of a user causes the chair or ladder to sink unevenly, the weight of a masonry pier and the weight of the building components, occupant loads, or snow loads on the pier can cause the footing to sink unevenly.  This sinking is called settlement, and when the sinking is uneven, it is called differential settlement.

There are also other soil related causes for uneven sinking.  Uneven frost heave can lift one side of a pier, and after the ice melts allow it to drop farther than the original elevation.  Differential sinking of the footing may also be caused by uneven shrinkage of the soil from moisture loss during a drought:  that is, just as a cheaper sponge shrinks when it dries out, soil also shrinks causing the objects on it to drop.  Uneven shrinkage causes uneven dropping.  Or when a pier is placed on an inadequately compacted backfill, such as the backfill in the excavation for a basement, the uneven compaction of the soil under the weight of the pier or moisture variations will cause an uneven sinking and a leaning of the pier.

If the leaning of the pier is due to one of these soil related causes, it is often accompanied by physical evidence of previous repairs with patching, adjustments, painting, replacement parts, etc.  These evidences often provide information to help determine the history and/or the cause of the leaning.

Thus, the real cause of the leaning of the masonry pier may determined by the body of evidence available in and around the subject pier.

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