Information to Build On
Do I Need Soil Borings and Soil Testing for My Residence
Building Codes: All of the major metropolitan areas in the greater Jackson/Metro typically enforce the 2012 International Residential Code for new residential construction. The code states: “Where quantifiable data created by accepted soil science methodologies indicate expansive, compressible, shifting, or other questionable soil characteristics are likely to be present, the building official shall determine whether to require a soil test to determine the soil’s characteristics at a particular location”. In short for new residential construction it is up to the discretion of the city building official to specify if a soils investigation is warranted. However, currently it is not mandatory for new construction, thus you can build a home without any soil information. If you will note the phrase “Where quantifiable data created by accepted soil science methodologies indicate expansive, compressible, shifting, or other questionable soil characteristics are likely to be present …”. Given the broad description, one of those conditions could realistically exist at any location in the country. However focusing on local geology, given that the Jackson Group Geologic Formation (Yazoo Clay) being a well documented expansive clay formation and extending beneath the entire Jackson/Metro area, not to mention other potentially problematic expansive clays located in areas throughout the State of Mississippi, the requirement for soil borings and soil testing for every new residential construction within Mississippi is warranted by the code's definition.
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Home Warranties: If you are thinking warranties should cover any issues … consider this. There are indeed 10-year “limited” warranties available on “major structural defects”. The key words in this phrase are “limited” and “major”. The only components with "major structural defect potential" whose failure is deemed to affect the safety of the building occupants (safety of the building occupants is a key phrase) are generally roof framing members, floor framing members, bearing walls, bearing columns, headers or lintels above doors and windows, girders, load-bearing beams and foundation walls and footings. Some load-bearing elements, such as roof sheathing and subflooring, are excluded because these are not considered major structural elements. Other elements that most homeowners would consider structural elements, such as interior partition walls, doors, windows, drywall and any type of exterior siding, are excluded because these are not load bearing. Even elements with "major structural defect potential" are generally not covered unless they pass the structural defects test. Most warranties have a criteria based on an "unlivable, uninhabitable" standard, rather than a precise measurement. The damage must generally be sufficient to cause the load-bearing element to fail and render the house unsafe and uninhabitable. These can be hard standards to meet. Generally speaking, the most common catalyst to meet these standards is fire. It can be difficult at times to discern whether an element has failed, and uninhabitable can mean it must be condemned by a local jurisdiction. In my experience, the bulk of foundation movement and distress generally results in un-level floors and predominately cosmetic issues as opposed to rendering “uninhabitable” or structurally unsound conditions. So by those criteria, most typical foundation movement and distress would not be covered by warranty. When it comes to your foundation, for my money I would not rely on any warranty.
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Residential Disclosures: I would now like to reference to language included in the disclosure agreement I signed for the purchase of my own house. It reads: Buyer understands that expansive soils/clays have been found to have caused foundation problems in certain areas of Mississippi. Buyer assumes the responsibility to have the subject property tested and/or inspected to determine if expansive soils/clay are present and if foundation damage has been caused thererby. Buyer acknowledges that a soil test has been recommended. This is typical boiler plate language for disclosure agreements in the area and puts the responsibility solely on you, the buyer. The responsibility is the buyer’s to protect themselves. I have performed a soil boring and soil testing at every house I have ever purchased for this very reason, to protect my investment.
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Why we are diligent before construction: One last and maybe most important point to consider is that the reason that we recommend thorough investigation, soil testing, and evaluation, and address problematic soil conditions prior to construction is because once a home is built, that is it…it’s on the ground. There is no going back and re-building it, nor can you go back and mitigate soil issues after the fact. The lion’s share of issues with foundations locally is generally expansive clay. The most problematic property of expansive clay is that it will expand and shrink as soil moisture changes. This will occur as long as the clay is present. It is next to impossible to modify a site such that the moisture in the ground is not going to change to some degree over the years and seasons, even with the best of drainage efforts. Also given that conditions are dependent primarily upon moisture, if prevailing weather is steady for a long period time, movement may not manifest for many years. It is not unheard of for a house to be constructed for 10 or 12 years before signs of movement are noticed, it just depends on the perimeter conditions of the house and the prevailing weather. It is also not unheard of for foundations to steadily shift for 10 or 12 years, due to the generally slow and steady absorption rates of clays. And this does not account for utility leaks that could compound the problem. Utility leaks can happen for any number of reasons and they feed moisture into ground the same as weather does, and they can certainly cause significant problems when in an expansive clay environment. In short, if potential expansive clay issues are not discovered and addressed properly at the time of construction, there is a high probability that a new foundation will experience some degree of movement throughout its working life, and most times even if "foundation repairs" are performed movement will persist.
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General Takeaway: Any structure that is going to be constructed on the ground is going to perform only as well as the ground on which it is constructed. One of my college professors once told me that the only time you don’t need a soil boring is if you are going to hang a new structure in the air from a skyhook.
Consider the average cost of a foundation repair is from about $3,000.00 to $5,000.00, and much greater in some situations. And realistically, most “foundation repair” is going to be a band aid at best, will likely not address or tackle the real problem, and most likely will not be a permanent fix. As an example, I was recently provided for review a cost estimate submitted by a popular foundation repair company for a home to install 9 re-leveling piles...for a cost of $12,000.00.....for 9 piers. Reviewing the situation, the house does not need piers, piers may end up causing more of a problem than a fix, and there was no attempt by the repair company to actually find out what was causing the problem. Another much more extreme case I encountered was a home that had been subject to extensive movement due to settling soils. The purchase price of the home was around $350,000.00, the initial estimate for repair.....$420,000.00. In contrast, the average residential geotechnical investigation or soil boring generally does not exceed about $1,500.00, and is more often around $500.00 to $1,000.00. My question is, is there anyone who can afford not to have a soil boring ? Anyone is better served by taking the time to confirm the subsoil is in good condition as opposed to roll the dice and assume it is and just wait to see what happens.
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Proper geotechnical engineering studies for residential projects will result in a quality foundation system. This will also significantly reduce the potential liability problems to the builders/designers. In general the cost of these services is minimal compared to the total coast of the project and potential foundation repair cost (generally less than about 1% of the construction cost). I would strongly urge that prior to constructing a new home or buying a constructed home, do all of your due diligence and have a qualified engineer perform soil borings and soil testing and investigate the subsurface conditions and render an opinion as it relates to construction, purchase, potential issues, or repair. ABTS can provide a detailed investigation and engineering direction as to lot development and mitigation, if necessary.