A home’s foundation is not a self-supporting structure. All homes that sit on top of foundations are supported on the ground beneath, and that ground beneath the foundation is made up of natural earth and is subject to our changing environmental conditions. In order for a home’s foundation structure to function properly, the ground beneath needs to be modified to prevent environmental (and other) conditions from impacting the foundation above.
During the design process, a geotechnical engineer will be consulted to determine the existing soil conditions. The geotechnical engineer’s work process begins with a site visit and soil sample collection. The soil samples will be collected in the area of the planned foundation so that the information gathered about the composition of the soil can be applied to the foundation design. Of course, the geotech could thoroughly analyze every square foot of soil beneath the planned foundation to get a more accurate idea of the soil’s composition, but there is a trade off in cost, and such detailed analysis is often ambiguous and not advisable. Once the soil samples are analyzed, the geotechnical engineer will provide recommendations for foundation design and formalize these recommendations in a report that is provided to the structural engineer and the rest of the design team.
With the geotechnical recommendations in hand, the structural engineering team will get to work on the foundation design. The civil engineering team will work in parallel on the grading design to ensure no drainage flows toward the foundation. As you will see in the list below, moisture is the ultimate nemesis for your home’s foundation! Changing moisture conditions is the root cause of a majority of foundation failures. Other failures can be attributed to professional incompetence or environmental disasters such as earthquakes, but we won’t cover these outliers here.
Water is the enemy when it comes to foundation design. The civil engineering design team will create a grading plan that will keep water flowing away from your home. The civil team will need to adhere to local standards as well as statewide building code (unless overridden by local standards). The current building code requires the natural ground to slope at 5% away from your home’s foundation for 10 feet, at which point the water will be carried away in a swale that is sloped at a minimum of 1% grade. It is common practice in today’s market, however, to design side yards with less than a 10 foot setback. In this case, the ground should slope away from the foundation and the fence at 5%, and a swale will carry the water away at a minimum slope of 2%. These standards are fairly new, so in home renovations and additions, these slopes may not be achievable, but the drainage should still flow away from the foundation no matter what. The onus does not stop with the Civil Engineer for this highly critical aspect of foundation design, though. The landscaping contractor that constructs the slopes and the inspector that approves the construction are also responsible for ensuring this critical component functions properly.
The design and construction team can control the grading design, but sometimes accidents happen, and water infiltration can be outside our control. If you have a plumbing leak, it is critical that it gets repaired immediately so as not to leak too much moisture into the ground which can change the soil properties. We will learn more about soil properties in the next section.
As previously mentioned, the geotechnical engineer is responsible for determining the existing soil conditions. In some cases, recommendations may include soil amendment, in which more appropriate soils for the planned construction are mixed in with the existing soil to create a stronger base for the foundation to sit on. In more extreme cases, the existing soil could be completely removed and replaced with imported material in the area of the foundation if the existing material is completely non-suitable. In cases like these, it is critical that contractors adhere to the geotechnical engineer’s recommendations because the integrity of the entire home’s structure depends on it.
It is not possible to know every detail about every square inch of soil, and the geotechnical engineer will be as efficient as possible in acquiring enough sample material to determine the site conditions. In some cases, they may make a recommendation that more sampling is needed, and of course more sampling means more cost. Not all clients or homeowners will want to spend this money, but it could be the reason for foundation failures in the future, so it is always in the best interest of the client or homeowner to take their geotechnical engineer’s recommendations seriously.
Even when the design team believes they have the best available information for a complete design, the soil could experience shrinkage and expansion (swell) that was not accounted for. Soil shrinkage and settlement could occur unevenly across a foundation and this would cause cracking over time. This is more common in expansive soils like clay. It is important to take special precautions when working with clayey soils.
Of course, if you are working with Design Everest, you will be working with licensed professionals with a high level of attention to detail and a long history of successful projects, but these projects require the careful coordination of many different professionals. As you have seen throughout this article, there are many transition points along the way where information is handed off between disciplines, and sometimes this is an iterative process. It is important that your design team is able to take their time in the design process to ensure no small detail is missed, and consistency is maintained across the entire project team. Professional teams can be assembled from a number of different organizations, and if they are not familiar with each other, some details can slip through the cracks. It is highly recommended that you accept your consultant’s recommendations if they refer you to a specific professional. This will ensure they approve of the professionals’ work flow and have worked successfully with them in the past.
In the case where information is being handed off between team members, some information can be lost in translation or lost in assumptions about another team member’s work capacity or ethic. You should be doing your due diligence as a homeowner to ensure you are comfortable with the team you’ve assembled, because if you are not, you could end up with poor performing consultants who miss some details in a rush and therefore end up with a poor design. It may not be “wrong,” but it may not have been properly planned in order to provide you with the highest level of service and quality product. A sub-par design product could be the reason your foundation fails!
Design Everest always holds our teams to the highest standards of quality and is able to move efficiently through your projects because we have assembled a team we can trust.
.Environmental considerations are another potential reason for your foundation’s failure that is out of our control. Extremely hot weather can pull moisture out of the soil around your foundation which could cause movement and therefore cracking. It is important to water your lawn in extremely hot conditions. Additionally, large trees near your foundation can be dangerous. Tree roots pull a surprising amount of water out of the ground, and can again cause soil movement and foundation cracking. It is important to keep your trees hydrated, especially when it’s hot!
At Design Everest, a team of highly skilled and experienced engineers work together to make sure the foundation of your building is built to last and withstand the above mentioned reasons for damage. Give us a call on (877) 704-5687 for a FREE CONSULTATION and quote!