Concrete Cracks and Expansive Soils – Unavoidable Movement

Date Published: August 26, 2019

A close examination of anything in a house will reveal small details that often go overlooked.  At Scott Home Inspection, we specialize in taking time to look for these details.  Oftentimes, minor details from many different areas of a house can produce a much clearer picture of larger developing conditions.

For example, superficial drywall cracking around a door jamb may not mean very much on its own, but can be a small piece of evidence of structural movement when placed alongside other evidence found in a house.

Similarly, cracks found in concrete installations around a house may not be evidence of improper installation or a larger problem, but may just be caused by normal expansive soil movement.

Concrete cracks in a walkway

What are expansive soils?

Every major population center in Colorado is located at least partially on expansive soils.  Expansive soils contain clay which expands when it comes into contact with moisture.  The expansive soils in a given area dictate which types of structures are permissible and how they are to be built.  This is part of the reason that some developments are built with basements and others are built with crawlspaces.

For decades, developments were designed and houses were built with very little consideration for grading and drainage, after all, most of the Front Range of Colorado is a high desert climate with very little annual precipitation.  The overall grading in a neighborhood built through the ’50s may appear “flat” for instance.

Over time it became abundantly clear that even with the relatively small amount of 15 inches of annual rainfall in Colorado, this water must be very carefully controlled to reduce the stress of the expanding soils on concrete systems around a house, including the concrete foundation.

What can expansive soils actually do?

As home inspectors in Colorado, we expect to see cracks in nearly every concrete surface on most of the houses that we inspect.  You just need to know where to look and pay attention to the very minor details.  Exterior concrete surfaces like a driveway, walkway, and patio are designed to accommodate some movement and cracking.  Concrete does two things, it cures and then cracks.

This is the reason that there are “lines” throughout concrete installations.  These are “control joints” and “expansion joints.” As the clay soils hold water and expand, you will begin to see cracks in concrete ranging from barely noticeable hairline cracks all the way to significant heaving damage, which would require replacement.