A home is often the biggest single expense an individual or family will make during their lifetime so to maintain it well and keep it in good condition is critical. There are thousands of components that go into the structure of a house. Some of the components will be subject to the elements of nature, such as temperature changes, precipitation, winds, and soil movement. This interplay of natural forces causes expansion and contraction or “give” in the home from the foundation up. One of the most indispensable and crucial structural components of a home is its foundation, and it is critical that homeowners maintain it properly, especially in Colorado.

Along Colorado’s Front Range, there are expansive soils that swell when they get wet and shrink as they dry out, often causing movement beneath a house. In fact, a very large portion of Colorado is subject to expansive soils as shown in this map of Colorado. It is required by law for new home builders to inform buyers of expansive soils and provide a soils report.

In addition to expansive soils, a foundation’s walls are subject to extreme temperature differentials. Outside portions of the foundation wall below ground usually have a constant temperature of about 50 degrees while the inside part of the wall will vary in temperature depending on the temperature to which the residence basement is heated. Portions of the foundation wall above ground are subjected to temperature variations of 20 degrees below zero to over 100 degrees. All of this can cause cracking in foundations and concrete flatwork. There will always be some amount of cracking, and builders have tolerance levels in their warranties that determine when the amount of cracking will affect integrity and safety.

The foundation walls of modern homes are designed by an engineer based on the soils report on the site the home is being built upon. The swell rate of the soils at a specific site will dictate the type of foundation and basement floor that will be used to give the home the best possible stability. In areas where there is no soil swelling, a home is often built on a foundation with spread footers. Due to the presence of expansive soils in Colorado, it is rare in a new home today that the engineer will suggest using a spread footer system. Modern design could include caissons drilled to bedrock, floating basement slabs, engineered basement slabs, wood basement floors, French Drains with a sump pump, and other options. 

No matter what foundation system is selected, it is imperative to have proper drainage around the house to keep the underlying soils dry and free of large swings in moisture content. Large amounts of water collecting near the foundation can cause problems no matter how solid the foundation system is. In the Boulder area during the 2013 flood, homeowners learned very quickly whether or not their homes had proper drainage. Since we received so much rain in that storm, even homes with good drainage had water in the basement due to seepage from the ground up. The most important part of the drainage system is maintaining a positive grade around the foundation walls for the first 10 feet from the foundation. Next, is making sure that the gutters and downspouts are clean, free of leaks, and are properly directing water away from the foundation. Any French Drain/sump pump system should be checked at least once a year to make sure everything is functioning.

Sprinkler systems installed next to foundation walls can cause huge problems when they leak. I know of a house in which the sprinkler line broke and water ran for more than a week under the home while the owners were on vacation. That much water in an expansive soil area can lift your whole house! The bottom line is that you should not have sprinkler systems or landscaping requiring water next to the foundation of your home.

The garden hose sillcock can be a big problem too. In areas where it freezes in winter, sillcocks with the valve inside the wall are used to prevent the connection from freezing. A common problem occurs when the homeowner leaves the hose on during the winter. The outwards pressure of the ice inside the hose and valve can cause the sillcock to break inside the wall. When it thaws out, water can start flowing down next to the foundation. Depending on the break location, it might be leaking inside the wall without the homeowner knowing it until the flood has happened!

In Colorado, it is pretty rare to have a 100% crack free foundation and concrete work, but a proper design for the specific lot, maintaining the grade and the drainage system, will ensure the least amount of problems due to expansive soils in our area.

By Duane Duggan. Duane graduated with a business degree and a major in real estate from the University of Colorado in 1978. He has been a Realtor^® in Boulder since that time. He joined RE/MAX of Boulder in 1982 and has facilitated over 2,500 transactions over his career, the vast majority from repeat and referred clients. Living the life of a Realtor and being immersed in real estate led to the inception of his book, Realtor for Life. For questions, e-mail duaneduggan@boulderco.com, call 303.441.5611 or visit BoulderPropertyNetwork.com.

Distribution of swelling soils and bedrock (shaded areas) in Colorado.