What is foundation settlement?
Settlement is downward vertical movement. Many of our structural engineering case studies involve foundation settlement.
What causes settlement?
Foundation settlement can result from one or many conditions.
- Additional loading. Adding weight to a structure can exceed the capacity of the supporting soil, such as adding a new "heavier" roof covering, a deck, or a second story addition.
- Removing support. Taking a support post out of a basement for a "home theater project" will increase the load on adjacent posts or footings, even if a larger beam is used. Remaining supports must be adequate to support the load change without movement over time.
- Improper construction methods.
- Excavation or compaction errors. Foundation excavation mistakes are "buried". If the excavation is made in the wrong location, or to the wrong depth, the excavator may try to backfill the mistake without taking appropriate measures to properly compact the soil.
- Improper footing construction. The soil may be weaker than assumed, and require a wider footing to properly support the load. The builder may not have requested a soil report, or there may have been a mistake on the construction drawings. Or the builder may not have noticed an increased footing size on the drawings.
- Weather conditions. Extreme weather, whether drier or wetter than usual can cause shrinkage or swelling of some soils, resulting in foundation movement.
- Surface water drainage. Improper drainage can lead to over saturation of one area, which can contribute to foundation movement.
- Vegetation. Some trees remove hundreds of gallons of water per day from the soil. If the root system migrates beneath a foundation, the resulting soil shrinkage can cause foundation damage.
- Animal activity. Burrowing animals can undermine a foundation and cause costly damage. Beware of ground hogs or ground squirrels, chipmunks, rabbits, or other rodents that may want to take up residence close to your foundation. They are fun to feed and watch, but they are very expensive to share space with.
Are all cracks from settlement?
No. Cracks can result from concrete curing shrinkage, chemical degradation, from lateral soil pressure, from expansive soil beneath a slab or behind a wall, from excessive stress, or from vibration such as from near by blasting or heavy equipment movement. Nearby excavation can also cause settlement if proper shoring methods are not used.
Foundation cracks can also occur if the forms are removed too soon, or if the wall is backfilled before the concrete has adequate strength, or if the concrete lacks proper reinforcing.
Heavy equipment collisions, over compacting the soil, or getting a heavy machine or vehicle too close to a wall or slab can also cause damage as operators make mistakes during construction.
Termite activity can cause cracking that looks like that caused by settlement. Getting a second opinion can often help you spend your repair dollars in the right place.
How should a crack be fixed?
Before a crack is fixed, the cause should be identified and remedied. Spending money on a crack repair may not correct the problem, and may worsen the condition that caused the crack.
My builder is an engineer. Why should I get others involved in my project?
You may have all the expertise you need. But, getting a second opinion may help avoid problems. A lot of details go into a successful project, and some problems take years to reveal themselves.
Engineering, like medicine, is a diverse profession. Most engineers start their careers in broad categories like electrical, mechanical, civil, architectural, or computer science, concentrating in more specialized areas as they advance. Basement Engineering and Structural Technologies LLC is a consulting firm composed of licensed professional engineers with extensive local commercial, industrial, and residential construction experience, specializing in foundation inspection, root cause failure analysis, and structural repair design, in consideration of geotechnical engineering soil properties.
Can you help us win a law suit?
You should consult a licensed attorney for legal advice. BEST LLC can give you professional engineering assessments of structural damage or foundation problems. Our staff includes experienced experts, that can assist with court room testimony, and we can help you document conditions and identify the science based probable cause. Often, the clients best investment is in well reasoned repairs, rather than legal remedies.
How much does it cost to dry up a damp, weepy, creepy basement?
If you are considering the purchase of a second property (or first, for that matter), but it has a problem basement, let us tell you how to address that bad basement problem.