Chimney, porch or steps pulling away from the house

Why these move

Separate concrete, separate behaviour

Porches, patios and steps are commonly poured after the house slab and are not tied into it. They ride on the top few inches of soil, the part that shrinks and swells the most.

A masonry chimney is a tall, narrow load on one small patch of ground. A little settlement at the base becomes a visible lean at the roofline.

Roof water is a frequent culprit. A downspout that empties beside a porch washes soil out from under it.

At the inspection

What a company checks

Whether the chimney stands on part of the house slab or on a footing of its own, and how far out of plumb it is.

Whether the porch is separate flatwork or carries part of the roof. A porch that holds up columns and a roof is structure, not paving.

The house slab next to the gap. If the wall, floor and doors there are sound, the problem may stop at the porch.

If it needs repair

What might be proposed

For a chimney, piers under its footing to stop the movement and, where practical, draw it back toward the wall.

For a sunken porch or walk, lifting the concrete by pumping grout or expanding foam beneath it, or breaking it out and pouring it again.

Afterwards the joint is sealed so rain does not run down behind the brick.

In the meantime

Sensible precautions

If the chimney has shifted, have the flue looked at before you light the fireplace again.

Measure the gap at the top and bottom and write it down with the date. A gap that has not changed in a year is a different conversation from one that grew over a summer.