Why aren't the columns on my porch straight?

expert EXPERT April 26, 2007

Most of the time, it is safe to assume that a column was installed straight and plumb. Columns may shift because of

• inappropriate foundations and footings
• soil erosion
• frost heave
• mechanical damage (e.g., vehicle impact)
• greater loads than were intended
• eccentric loads (off center)
• deterioration of the column or its connection points
• columns poorly secured at their top or bottom

Columns that have moved may allow the structure they support to fail. These columns may be expensive to stabilize.

To check columns: Look carefully at columns, particularly the top and bottom, for evidence of movement. Look at the column from several angles. When standing on the street looking at a house, columns that are out of plumb to the left or right will be visible, but a column that is out of plumb leaning toward the street may not be noticeable. Push on the column near the bottom and near the top, if possible, to ensure that it's well anchored.

If a column is near a laneway or driveway and has moved or shifted, that may suggest vehicle impact.

Where columns are made of dissimilar materials (bottom brick, top wood) a natural hinge is created and any eccentric loading (load applied off center of the column) will cause the column to bend at the hinge point. A gap will develop between the two sections.

Wood columns sitting in the soil will rot. The bottom of a metal column will rust if it's too close to the soil. Metal and wood columns should have footings that extend above ground more than four inches.